Ändra sökning
Avgränsa sökresultatet
1234567 151 - 200 av 320
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 151. Jarret, Mark
    et al.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Child, R. K.
    Jimenez, C.
    Courcoux, N.
    Emde, C.
    Heygster, G.
    Sreerekha, T. R.
    Eriksson, P.
    Rydberg, B.
    Foster, P. R.
    Rose, T.
    Davis, C.
    Evans, K. F.
    Heymsfield, A.
    Lohmann, U.
    Stubenrauch, C.
    Establishment of mission and instrument requirements to observe cirrus clouds at sub-millimetre wavelengths: Final report, ESTEC contract no. 19053/05/NL/AR2007Rapport (Övrigt vetenskapligt)
  • 152.
    Jimenez, Carlos
    et al.
    Observatoire de Paris, Laboratoire d'Etudes de Rayonnement et de la Matire en Astro-physique, Centre National de la Recherche Scientifique, Paris.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Performance simulations for a submillimetre-wave satellite instrument to measure cloud ice2007Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr Suppl.2, 129-149 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of a conically scanning satellite instrument for the measurement of cloud ice was studied. The instrument measures radiances in 12 channels placed around the 183, 325 and 448 GHz water vapour lines and the 243, 664 and 874 GHz window channels, and is designed to provide estimations of ice water path (IWP), the equivalent sphere diameter (DME), and the median ice mass height (ZME). Overall median relative errors of around 20% for IWP, 33 µm for DME, and 240 m for ZME for a midlatitude winter scenario, and 17% for IWP, 30 µm for DME, and 310 m for ZME for a tropical scenario were found. Detection limits (relative retrieval error reaching 100%) of around 2 gm-2 were estimated for both scenarios. The performance of a five-receiver instrument, where either the 664 or 874 GHz channel is dropped, was close, but with increased errors for very thin and high clouds. A trade-off between having the 874 GHz receiver or two infrared channels at 10.7 and 12 µm emerged, as very similar performance was found between the six-receiver instrument and the five-receiver instrument with the infrared channels. Another trade-off between receiver selection and noise was also apparent, with some of the four-receiver selections operating at half noise levels being able to compete with the standard six-receiver instrument. Dual-polarized measurements were also tested, but they did not significantly improve the retrievals of IWP or DME.

  • 153. Jiménez, Carlos J.
    et al.
    Gulkis, Samuel L.
    Beaudin, Gérard
    Encrenaz, Th. H.
    Eriksson, Patrick
    Chalmers University of Technology.
    Kamp, Lucas W.
    Lee, S.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sub-millimeter observations of the terrestrial atmosphere during an Earth flyby of the MIRO sounder on the Rosetta spacecraft2013Ingår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 82-83, 99-112 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sub-millimeter spectra recorded by the MIRO sounder aboard the Rosetta spacecraft have been used at the time of an Earth flyby (November 2007) to check the consistency and validity of the instrumental data. High-resolution spectroscopic data were recorded in 8 channels in the vicinity of the strong water line at 557 GHz, and in a broad band continuum channel at 570 GHz. An atmospheric radiative transfer code (ARTS) and standard terrestrial atmospheres have been used to simulate the expected observational results. Differences with the MIRO spectra suggest an anomaly in the behavior of four spectroscopic channels. Further technical investigations have shown that a large part of the anomalies are associated with an instability of one of the amplifiers. The quality of the MIRO data has been further tested by inverting the spectra with an atmospheric inversion tool (Qpack) in order to derive a mesospheric temperature profile. The retrieved profile is in good agreement with the one inferred from the Earth Observing System Microwave Limb Sounder (EOS-MLS). This work illustrates the interest of validating instruments aboard planetary or cometary spacecraft by using data acquired during Earth flybys.

  • 154.
    Johansson, Mattias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evaluation of Sensor Solutions & Motor Speed Control Methods for BLDCM/PMSM in Aerospace Applications2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The goal of this thesis was to evaluate sensors and motor speed control methods for BLDC/PMSM motors in Aerospace applications. The sensors and methods were evaluated by considering accuracy, robustness, cost, development gain and parameter sensitivity. The sensors and methods chosen to simulate were digital Hall sensors and sensorless control of BLDC motors. Using Matlab Simulink/Simscape some motor speed control methods and motor speed estimation methods were simulated using the Hall sensors and sensorless control as a basis. It was found that the sensorless control methods for BLDC motors couldn't estimate the speed accurately during dynamic loads and that the most robust and accurate solution based on the simulations was using the digital Hall sensors for both speed estimation and commutation and this was tested on a hardware setup.

  • 155.
    John, V. O.
    et al.
    University of Miami.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuvatov, M.
    Universität Bremen.
    Soden, B. J.
    University of Miami.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Toward a long-term homogenized UTH data set derived from satellite microwave measurements2006Ingår i: Microwave remote sensing of the atmosphere and environment. V. / [ed] Azita Valinia; Seiho Uratsuka; Tapan Misra, Bellingham, Wash: SPIE - International Society for Optical Engineering, 2006, 64100K- s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article presents some ideas and issues related to the creation of a long-term upper tropospheric humidity (UTH) data set using satellite based microwave measurements. Polar orbiting satellites have been measuring UTH for more than a decade now. There are three microwave instruments which can measure UTH from Space: Special Sensor Microwave/Temperature-2 (SSM/T2), Advanced Microwave Sounding Unit-B (AMSU-B), and Microwave Humidity Sounder (MHS). These instruments have channels at 183.31±1.00GHz which are sensitive to UTH. Retrieval of UTH and cloud issues are discussed in detail. Advantage of microwave measurements of UTH over infrared measurements are demonstrated. Preliminary results on the inter-calibration of these instruments are also shown.

  • 156.
    John, Viju O.
    et al.
    Met Office Hadley Centre, Exeter.
    Allan, Richard P.
    Department of Meteorology, University of Reading.
    Bell, William
    Met Office Hadley Centre, Exeter.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Assessment of intercalibration methods for satellite microwave humidity sounders2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 10, 4906-4918 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three methods for ntercalibrating humidity sounding channels are compared to assess their merits and demerits. The methods use the following: (1) natural targets (Antarctica and tropical oceans), (2) zonal average brightness temperatures, and (3) simultaneous nadir overpasses (SNOs). Advanced Microwave Sounding Unit-B instruments onboard the polar-orbiting NOAA 15 and NOAA 16 satellites are used as examples. Antarctica is shown to be useful for identifying some of the instrument problems but less promising for intercalibrating humidity sounders due to the large diurnal variations there. Owing to smaller diurnal cycles over tropical oceans, these are found to be a good target for estimating intersatellite biases. Estimated biases are more resistant to diurnal differences when data from ascending and descending passes are combined. Biases estimated from zonal-averaged brightness temperatures show large seasonal and latitude dependence which could have resulted from diurnal cycle aliasing and scene-radiance dependence of the biases. This method may not be the best for channels with significant surface contributions. We have also tested the impact of clouds on the estimated biases and found that it is not significant, at least for tropical ocean estimates. Biases estimated from SNOs are the least influenced by diurnal cycle aliasing and cloud impacts. However, SNOs cover only relatively small part of the dynamic range of observed brightness temperatures

  • 157.
    John, Viju O
    et al.
    Met Office Hadley Centre, Exeter.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Allen, Richard P.
    Department of Meteorology, University of Reading.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Parker, David E.
    Met Office Hadley Centre, Exeter.
    Soden, Brian J.
    Rosenstiel School of Marine and Atmospheric Science, University of Miami.
    Clear-sky biases in satellite infrared estimates of upper tropospheric humidity and its trends2011Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use microwave retrievals of upper tropospheric humidity (UTH) to estimate the impact of clear-sky-only sampling by infrared instruments on the distribution, variability, and trends in UTH. Our method isolates the impact of the clear-sky-only sampling, without convolving errors from other sources. On daily time scales, IR-sampled UTH contains large data gaps in convectively active areas, with only about 20-30 % of the tropics (30 degrees S-30 degrees N) being sampled. This results in a dry bias of about -9 % RH in the area-weighted tropical daily UTH time series. On monthly scales, maximum clear-sky bias (CSB) is up to -30 % RH over convectively active areas. The magnitude of CSB shows significant correlations with UTH itself (-0.5) and also with the variability in UTH (-0.6). We also show that IR-sampled UTH time series have higher interannual variability and smaller trends compared to microwave sampling. We argue that a significant part of the smaller trend results from the contrasting influence of diurnal drift in the satellite measurements on the wet and dry regions of the tropics.

  • 158.
    John, Viju O.
    et al.
    Met Office Hadley Centre, Exeter.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Atkinson, Nigel
    Met Office Hadley Centre, Exeter.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Monitoring scan asymmetry of microwave humidity sounding channels using simultaneous all angle collocations (SAACs)2013Ingår i: Journal of Geophysical Research: Atmospheres, ISSN 2169-8996, Vol. 118, nr 3, 1536-1545 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simultaneous all angle collocations (SAACs) of microwave humidity sounders (AMSU-B and MHS) on-board polar orbiting satellites are used to estimate scan-dependent biases. This method has distinct advantages over previous methods, such as that the estimated scan-dependent biases are not influenced by diurnal differences between the edges of the scan and the biases can be estimated for both sides of the scan. We find the results are robust in the sense that biases estimated for one satellite pair can be reproduced by double differencing biases of these satellites with a third satellite. Channel 1 of these instruments shows the least bias for all satellites. Channel 2 has biases greater than 5 K, thus needs to be corrected. Channel 3 has biases of about 2 K and more and they are time varying for some of the satellites. Channel 4 has the largest bias which is about 15 K when the data are averaged for 5 years, but biases of individual months can be as large as 30 K. Channel 5 also has large and time varying biases for two of the AMSU-Bs. NOAA-15 (N15) channels are found to be affected the most, mainly due to radio frequency interference (RFI) from onboard data transmitters. Channel 4 of N15 shows the largest and time varying biases, so data of this channel should only be used with caution for climate applications. The two MHS instruments show the best agreement for all channels. Our estimates may be used to correct for scan-dependent biases of these instruments, or at least used as a guideline for excluding channels with large scan asymmetries from scientific analyses.

  • 159.
    John, Viju O.
    et al.
    Met Office Hadley Centre, Exeter.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Candy, Brett
    Met Office Hadley Centre, Exeter.
    Saunders, Roger W.
    Met Office Hadley Centre, Exeter.
    Perker, David E.
    Met Office Hadley Centre, Exeter.
    Understanding intersatellite biases of microwave humidity sounders using global simultaneous nadir overpasses2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, D02305- s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simultaneous nadir overpasses (SNOs) of polar-orbiting satellites are most frequent in polar areas but can occur at any latitude when the equatorial crossing times of the satellites become close owing to orbital drift. We use global SNOs of polar orbiting satellites to evaluate the intercalibration of microwave humidity sounders from the more frequent high-latitude SNOs. We have found based on sensitivity analyses that optimal distance and time thresholds for defining collocations are pixel centers less than 5 km apart and time differences less than 300 s. These stringent collocation criteria reduce the impact of highly variable surface or atmospheric conditions on the estimated biases. Uncertainties in the estimated biases are dominated by the combined radiometric noise of the instrument pair. The effects of frequency changes between different versions of the humidity sounders depend on the amount of water vapor in the atmosphere. There are significant scene radiance and thus latitude dependencies in the estimated biases and this has to taken into account while intercalibrating microwave humidity sounders. Therefore the results obtained using polar SNOs will not be representative for moist regions, necessitating the use of global collocations for reliable intercalibration.

  • 160.
    John, Viju Oommen
    et al.
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Courcoux, N.
    A cautionary note on the use of Gaussian statistics in satellite-based UTH climatologies2006Ingår i: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 3, nr 1, 130-134 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter presents a cautionary note on the assumption of Gaussian behavior for upper tropospheric humidity (UTH) derived from satellite data in climatological studies, which can introduce a wet bias in the climatology. An example study using European Centre for Medium-Range Weather Forecasts reanalysis data shows that this wet bias can reach up to 6 %RH, which is significant for climatological applications. A simple Monte Carlo approach demonstrates that these differences and their link to the variability of brightness temperatures are due to a log-normal distribution of the UTH. This problem can be solved by using robust estimators such as the median instead of the arithmetic mean.

  • 161.
    John, Viju Oommen
    et al.
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Engeln, A. von
    EUMETSAT, Darmstadt.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Kuhn, Thomas
    University of Köln, Physikalisches Institut.
    Brocard, E.
    University of Bern, Institue of Applied physics.
    Koenig-Langlo, G.
    Alfred Wegener Institute for Polar and Marine Research, Bremerhaven.
    Understanding the variability of clear-sky outgoing long-wave radiation based on ship-based temperature and water vapour measurements2006Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 132, nr 621, 2675-2691 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-resolution radiative transfer model calculations with the Atmospheric Radiative Transfer Simulator (ARTS) were used to simulate the clear-sky outgoing long-wave radiative flux (OLR) at the top of the atmosphere. The unique set of radiosonde data collected by the research vessel Polarstern of the Alfred Wegener Institute for Polar and Marine Research during 27 expeditions in the years 1982 to 2003 was used to investigate the sources of clear-sky OLR variability for ocean areas in different climate zones and seasons. For this dataset, tropospheric temperature variations contribute approximately 33 W m(-2) OLR variability. tropospheric relative humidity variations 8.5 W m(-2), and vertical structure 2.3-3.4 W m(-2). Of these, 0.3-1.0 W m(-2) are due to structures on a vertical scale smaller than 4 km, which cannot be resolved by conventional remote-sensing instruments. It was also found that the poor absolute accuracy of current humidity data in the upper troposphere, approximately 40% relative error in relative humidity, leads to a significant uncertainty in OLR of about 3.8 W m(-2) (for a midlatitude summer atmosphere), which should be put in the context of the double CO2 effect of only 2.6 W m(-2) (for the same atmosphere).

  • 162.
    Johnson, Jeffrey R.
    et al.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    III, J.F. Bell
    Arizona State University.
    Bender, S.
    Planetary Science Institute, Tucson.
    Blaney, D.
    Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Cloutis, E.
    University of Winnipeg, Manitoba.
    DeFlores, L.
    Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Ehlmann, B.
    California Institute of Technology, Pasadena.
    Gasnault, O.
    Université de Toulouse, CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Gondet, B.
    Institut d’Astrophysique Spatiale, Batîment 12, 91405 Orsay Campus.
    Kinch, K.
    Niels Bohr Institute, University of Copenhagen.
    Lemmon, M.
    Texas A&M University, College Station.
    Mouélic, S. Le
    Université de Nantes, Laboratoire de Planétologie et Géodynamique.
    Maurice, S.
    Université de Toulouse, CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Rice, M.
    California Institute of Technology, Pasadena.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars2015Ingår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, 74-92 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400–840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets’ housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (<1 nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich “raised ridges” tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600 nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the “blast zone” immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by the ChemCam passive measurements as well. Ongoing efforts to model and correct for this dust component should improve calibration of the relative reflectance spectra. This will be useful as additional measurements are acquired during the rover’s future examinations of hematite-, sulfate-, and phyllosilicate-bearing materials near the base of Mt. Sharp that are spectrally active in the 400–840 nm region.

  • 163.
    Johnston, Marston
    et al.
    Chalmers University of Technology, Chalmers University of Technology, Department of Earth and Space Sciences.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrik
    Chalmers University of Technology, Chalmers University of Technology, Department of Earth and Space Sciences.
    Forbes, R.M.
    European Centre for Medium-Range Weather Forecasts, Reading, ECMWF, Shinfield Park, Reading.
    Gettelman, Andrew
    National Center for Atmospheric Research, Boulder, Colorado.
    Räisänen, Petri
    Finnish Meteorological Institute, Helsinki.
    Zelinka, M.D.
    Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore.
    Diagnosing the average spatio-temporal impact of convective systems: part 2:a model intercomparison using satellite data2014Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, nr 16, 8701-8721 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The representation of the effect of tropical deep convective (DC) systems on upper-tropospheric moist processes and outgoing longwave radiation is evaluated in the EC-Earth3, ECHAM6, and CAM5 (Community Atmosphere Model) climate models using satellite-retrieved data. A composite technique is applied to thousands of deep convective systems that are identified using local rain rate maxima in order to focus on the temporal evolution of the deep convective processes in the model and satellite-retrieved data. The models tend to over-predict the occurrence of rain rates that are less than 3 mm 1 compared to Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA). While the diurnal distribution of oceanic rain rate maxima in the models is similar to the satellite-retrieved data, the land-based maxima are out of phase. Despite having a larger climatological mean upper-tropospheric relative humidity, models closely capture the satellite-derived moistening of the upper troposphere following the peak rain rate in the deep convective systems. Simulated cloud fractions near the tropopause are larger than in the satellite data, but the ice water contents are smaller compared with the satellite-retrieved ice data. The models capture the evolution of ocean-based deep convective systems fairly well, but the land-based systems show significant discrepancies. Over land, the diurnal cycle of rain is too intense, with deep convective systems occurring at the same position on subsequent days, while the satellite-retrieved data vary more in timing and geographical location. Finally, simulated outgoing longwave radiation anomalies associated with deep convection are in reasonable agreement with the satellite data, as well as with each other. Given the fact that there are strong disagreements with, for example, cloud ice water content, and cloud fraction, between the models, this study supports the hypothesis that such agreement with satellite-retrieved data is achieved in the three models due to different representations of deep convection processes and compensating errors.

  • 164.
    Johnston, Marston
    et al.
    Chalmers University of Technology.
    Eriksson, Patrik
    Chalmers University of Technology.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Jones, Colin
    SMHI.
    Forbes, R.M
    ECMWF, Shinfield Park, Reading.
    Murtagh, Donal
    Chalmers University of Technology, Department of Earth and Space Sciences.
    The representation of tropical upper tropospheric water in EC Earth V22012Ingår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, nr 11, 2713-2731 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tropical upper tropospheric humidity, clouds, and ice water content, as well as outgoing longwave radiation (OLR), are evaluated in the climate model EC Earth with the aid of satellite retrievals. The Atmospheric Infrared Sounder and Microwave Limb Sounder together provide good coverage of relative humidity. EC Earth's relative humidity is in fair agreement with these observations. CloudSat and CALIPSO data are combined to provide cloud fractions estimates throughout the altitude region considered (500-100 hPa). EC Earth is found to overestimate the degree of cloud cover above 200 hPa and underestimate it below. Precipitating and non-precipitating EC Earth ice definitions are combined to form a complete ice water content. EC Earth's ice water content is below the uncertainty range of CloudSat above 250 hPa, but can be twice as high as CloudSat's estimate in the melting layer. CERES data show that the model underestimates the impact of clouds on OLR, on average with about 9 W m -2. Regionally, EC Earth's outgoing longwave radiation can be ~20 W m -2 higher than the observation. A comparison to ERA-Interim provides further perspectives on the model's performance. Limitations of the satellite observations are emphasised and their uncertainties are, throughout, considered in the analysis. Evaluating multiple model variables in parallel is a more ambitious approach than is customary.

  • 165.
    Johnston, M.S.
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Forbes, R.M.
    European Centre for Medium-Range Weather Forecasts, Reading.
    Wyser, K.
    Swedish Meteorological and Hydrological Institute, Norrköping.
    Zelinka, M.D.
    Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore.
    Diagnosing the average spatio-temporal impact of convective systems: part 1: A methodology for evaluating climate models2013Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, nr 23, 12043-12058 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An earlier method to determine the mean response of upper-tropospheric water to localised deep convective systems (DC systems) is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009), several fields related to moist processes and radiation from various satellites are composited with respect to the local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the earlier study are the isolation of DC systems in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterisation of the DC-system-induced anomalies. The observed DC systems in this study propagate westward at similar to 4 ms(-1). Both the upper-tropospheric relative humidity and the outgoing longwave radiation are substantially perturbed over a broad horizontal extent and for periods > 30 h. The cloud fraction anomaly is fairly constant with height but small maximum can be seen around 200 hPa. The cloud ice water content anomaly is mostly confined to pressures greater than 150 hPa and reaches its maximum around 450 hPa, a few hours after the peak convection. Consistent with the large increase in upper-tropospheric cloud ice water content, albedo increases dramatically and persists about 30 h after peak convection. Applying the compositing technique to EC-Earth allows an assessment of the model representation of DC systems. The model captures the large-scale responses, most notably for outgoing longwave radiation, but there are a number of important differences. DC systems appear to propagate east-ward in the model, suggesting a strong link to Kelvin waves instead of equatorial Rossby waves. The diurnal cycle in the model is more pronounced and appears to trigger new convection further to the west each time. Finally, the modelled ice water content anomaly peaks at pressures greater than 500 hPa and in the upper troposphere between 250 hPa and 500 hPa, there is less ice than the observations and it does not persist as long after peak convection. The modelled upper-tropospheric cloud fraction anomaly, however, is of a comparable magnitude and exhibits a similar longevity as the observations.

  • 166.
    Kah, Linda C.
    et al.
    University of Tennessee, Knoxville.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Images from Curiosity: A New Look at Mars2015Ingår i: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, nr 1, 27-32 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface of Mars has been sculpted by flowing water and shaped by wind. During the first two years of its exploration of Gale Crater, the Mars Science Laboratory mission's Curiosity rover has recorded abundant geologic evidence that water once existed on Mars both within the subsurface and, as least episodically, flowed on the land surface. And now, as Curiosity presses onward toward Mount Sharp, the complexity of the Martian surface is becoming increasingly apparent. In this paper, we review the nature of the surface materials and their stories, as seen through the eyes of Curiosity.

  • 167.
    Kahanpää, Henrik
    et al.
    Finnish Meteorological Institute, Helsinki.
    Newman, C.E.
    Ashima Research, Pasadena.
    Moores, John E.
    Center for Research in Earth and Space Science, York University, Toronto, York University, Toronto, York University/Earth and Space Science and Engineering, North York, Ontario, York University, North York, Ontario.
    Zorzano, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Navarro, Sara
    Centro de Astrobiologia, INTA-CSIC, Madrid , Centro de Astrobiología (CSIC-INTA), Madrid, Centro de Astrobiologia, Madrid.
    Lepinette, Alain
    Centro de Astrobiología (CSIC-INTA), Madrid, Centro de Astrobiologia, INTA-CSIC, Madrid , Centro de Astrobiologia, Madrid.
    Cantor, Bruce
    Malin Space Science Systems.
    Lemmon, Mark T.
    Department of Atmospheric Sciences, Texas A&M University, Texas A&M University, College Station.
    Valentin-Serrano, Patricia
    CSIC-UGR - Instituto Andaluz de Ciencias de la Tierra (IACT), Granada, Centro de Astrobiologia, Madrid.
    Ullán, Aurora
    Centro de Astrobiologia, Madrid.
    Schmidt, W.
    Finnish Meteorological Institute, Helsinki.
    Convective vortices and dust devils at the MSL landing site: annual variability2016Ingår i: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 121, nr 8, 1514-1549 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two hundred fifty-two transient drops in atmospheric pressure, likely caused by passing convective vortices, were detected by the Rover Environmental Monitoring Station instrument during the first Martian year of the Mars Science Laboratory (MSL) landed mission. These events resembled the vortex signatures detected by the previous Mars landers Pathfinder and Phoenix; however, the MSL observations contained fewer pressure drops greater than 1.5 Pa and none greater than 3.0 Pa. Apparently, these vortices were generally not lifting dust as only one probable dust devil has been observed visually by MSL. The obvious explanation for this is the smaller number of strong vortices with large central pressure drops since according to Arvidson et al. [2014] ample dust seems to be present on the surface. The annual variation in the number of detected convective vortices followed approximately the variation in Dust Devil Activity (DDA) predicted by the MarsWRF numerical climate model. This result does not prove, however, that the amount of dust lifted by dust devils would depend linearly on DDA, as is assumed in several numerical models of the Martian atmosphere, since dust devils are only the most intense fraction of all convective vortices on Mars, and the amount of dust that can be lifted by a dust devil depends on its central pressure drop. Sol-to-sol variations in the number of vortices were usually small. However, on 1 Martian solar day a sudden increase in vortex activity, related to a dust storm front, was detected. 

  • 168.
    Kasai, Y.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kreyling, D.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Dupuy, E.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Baron, P.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Suzuki, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sato, T.O.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Nishibori, T.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mizobuchi, S.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Ozeki, H.
    Toho University, Funabashi, Chiba.
    Sugita, T.
    Luleå tekniska universitet.
    Fujiwara, M.
    Toho University, Funabashi, Chiba.
    Irimajiri, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Walker, K.A.
    University of Toronto.
    Bernath, P.F.
    Old Dominion University, Norfolk, Virginia.
    Boone, C.
    University of Waterloo.
    Stiller, G.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Clarmann, T. von
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Orphal, J.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Urban, J.
    Chalmers University of Technology.
    Murtagh, D.
    Chalmers University of Technology.
    Llewellyn, E.J.
    Institute of Space and Atmospheric Studies, University of Saskatchewan.
    Yasui, M.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Validation of stratospheric and mesospheric ozone observed by SMILES from International Space Station2013Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 6, nr 9, 2311-2338 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We observed ozone (O3) in the vertical region between 250 and 0.0005 hPa (~ 12–96 km) using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the Japanese Experiment Module (JEM) of the International Space Station (ISS) between 12 October 2009 and 21 April 2010. The new 4 K superconducting heterodyne receiver technology of SMILES allowed us to obtain a one order of magnitude better signal-to-noise ratio for the O3 line observation compared to past spaceborne microwave instruments. The non-sun-synchronous orbit of the ISS allowed us to observe O3 at various local times. We assessed the quality of the vertical profiles of O3 in the 100–0.001 hPa (~ 16–90 km) region for the SMILES NICT Level 2 product version 2.1.5. The evaluation is based on four components: error analysis; internal comparisons of observations targeting three different instrumental setups for the same O3 625.371 GHz transition; internal comparisons of two different retrieval algorithms; and external comparisons for various local times with ozonesonde, satellite and balloon observations (ENVISAT/MIPAS, SCISAT/ACE-FTS, Odin/OSIRIS, Odin/SMR, Aura/MLS, TELIS). SMILES O3 data have an estimated absolute accuracy of better than 0.3 ppmv (3%) with a vertical resolution of 3–4 km over the 60 to 8 hPa range. The random error for a single measurement is better than the estimated systematic error, being less than 1, 2, and 7%, in the 40–1, 80–0.1, and 100–0.004 hPa pressure regions, respectively. SMILES O3 abundance was 10–20% lower than all other satellite measurements at 8–0.1 hPa due to an error arising from uncertainties of the tangent point information and the gain calibration for the intensity of the spectrum. SMILES O3 from observation frequency Band-B had better accuracy than that from Band-A. A two month period is required to accumulate measurements covering 24 h in local time of O3 profile. However such a dataset can also contain variation due to dynamical, seasonal, and latitudinal effects

  • 169.
    Kasai, Yasuko
    et al.
    National Institute of Information and Communication Technology, Tokyo.
    Sagawa, Hideo
    National Institute of Information and Communication Technology, Tokyo.
    Kuroda, Takeshi
    Institute of Space and Astronautical Science, Chuoku, Sagamihara, Kanagawa.
    Manabe, Takeshi
    Osaka Prefecture University, Naka, Sakai.
    Ochiai, Satoshi
    National Institute of Information and Communication Technology, Tokyo.
    Kikuchi, Ken–ichi
    National Institute of Information and Comunications Technology, Koganei, Tokyo.
    Nishibori, Toshiyuki
    Japan Aerospace Exploration Agency.
    Baron, Philippe
    National Institute of Information and Communication Technology, Tokyo.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Hartogh, Paul
    Max-Planck-Institut für Solar System Research.
    Murtagh, Donal
    Chalmers University of Technology.
    Urban, Joachim
    Chalmers University of Technology.
    Schéele, Fredrik von
    Swedish Space Corporation.
    Frisk, Urban
    Swedish Space Corporation.
    Overview of the Martian atmospheric submillimetre sounder FIRE2012Ingår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 63-64, 62-82 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a submillimetre-wave atmospheric emission sounding instrument, called Far-InfraRed Experiment (FIRE), for the Japanese Martian exploration programme Mars Exploration with Lander-Orbiter Synergy (MELOS). The scientific target of FIRE/MELOS is to understand the dust suspended meteorology of the Mars. FIRE will provide key meteorological parameters, such as atmospheric temperature profiles for outside and inside dust storms, the abundance profile of the atmospheric compositions and their isotopes, and wind velocity profiles. FIRE will also provide the local time dependency of these parameters. The observational sensitivity of FIRE/MELOS is discussed in this paper. FIRE will explore the meteorological system of the Martian atmosphere including the interaction between its surface and atmosphere

  • 170.
    Kereluk, Jason A.
    et al.
    University of Toronto, Institute for Aerospace Studies.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Task-based optimization of reconfigurable robot manipulators2017Ingår i: Advanced Robotics, ISSN 0169-1864, E-ISSN 1568-5535, Vol. 31, nr 16, 836-850 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reconfigurable Manipulators are structurally redundant robots that utilize a subset of their joints to perform a specific task optimally. This paper presents a method of finding a task-based optimal configuration for a new type of reconfigurable robot manipulator, called the modular autonomously reconfigurable serial (MARS) manipulator. The reconfiguration optimization treats the joint space of the MARS manipulator as a 12-dimensional smooth configuration manifold. The manifold is discretized and ranked based on a variety of criteria, and then clustered into attractive and repellent regions. The user then specifies which regions are desired in the target configuration, and the manifold is reduced in dimension in order to maximize the number of attractive regions and minimize the number of repellent regions. Six manipulator configurations are synthesized using this approach, and their effectiveness is compared.

  • 171.
    Kereluk, Jason Alexander
    et al.
    Space Mechatronics Group, Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A New Modular, Autonomously Reconfigurable Manipulator Platform2015Ingår i: International Journal of Advanced Robotic Systems, ISSN 1729-8806, E-ISSN 1729-8814, Vol. 12, 71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper discusses the design and development of a new Modular, Autonomously Reconfigurable Serial manipulator platform for advanced manufacturing, termed as the MARS manipulator. The platform consists of i) an 18-Degree-of-Freedom (DOF) serial-link manipulator capable of locking any of its joints at any position in their continuous range, such that it can emulate fewer-DOF serial manipulators with different kinematic and dynamic parameters, and ii) an integrated simulation and design environment that provides control over the manipulator hardware as well as a toolset for the design, implementation and optimization of a desired manipulator configuration for a given task. The effectiveness of the MARS manipulator to adapt its configuration to various tasks is examined by assuming two well-known configurations, SCARA and articulated, and by performing a specific task with each of them. The variation in effectiveness of the two configurations in terms of the end-effector trajectory, end-effector accuracy and power consumption is discussed. Further, these configurations are optimized with respect to their performance accuracy, and compared to their pre-optimized versions. Finally, the accuracy model of the simulation is compared against the physical hardware system, running the same task.

  • 172.
    Kettig, Peter
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Benchmarking of C++ image processing libraries within the Euclid project2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this report, the issue of selecting a C++ image processing library for the Euclid science ground segment (SGS) is tackled. A new benchmark is proposed to objectively compare libraries according to both static, development-related, and dynamic, execution-related criteria.

    Instead of comparing isolated functions, a much more realistic scenario is implemented: a complete processing pipeline based on a use-case algorithm, called L.A. cosmic. Already existing in the SGS and used multiple times for the flagging of galactic cosmic rays (GCRs), this algorithm is the optimal choice for setting up the benchmark. This makes the results much more usable than with classical single- function benchmarks.

    First, the used tools as well as both categories are explained with their respective criteria listed, all tailored to the needs of the SGS. This also introduces the statistical profiling used throughout the project. Additionally, a scientific validation is introduced that monitors the accuracy of the implementations created.

    Afterwards, the benchmark is conducted and the results are presented and discussed. Indeed, including static criteria helps taking into account development and debugging time – key elements of the project life. Moreover, most library contenders are lacking important functions required for the implementation of the reference algorithm and are therefore excluded from further measurements. Documenting the missing or unclear functions gives then an overview about how user-friendly a library is to develop with.

    The scientific validation depicts that a missing function in one of the contenders and the resulting deviation from the reference results in a lower accuracy. Leaving out the problematic part of the pipeline improves the results, yet only with a higher amount of stars being misinterpreted as GCRs.

    The dynamic criteria report that all contenders perform better than a python reference version as well as a consistent linear dependency to the input image size, while also offering an approach to multi-core processing. Yet, the latter exhibits problems of some libraries to scale appropriately with more resources, leaving the results divided between the single- and multi-core setups for this benchmark.

    When taking this parameter of cores into account, the benchmark allows to recommend the most appropriate library to the SGS. 

  • 173. Kiefer, M.
    et al.
    Arnone, E.
    Dudhia, A.
    Carlotti, M.
    Castelli, E.
    Clarmann, T. von
    Dinelli, B. M.
    Kleinert, A.
    Linden, A.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Papandrea, E.
    Stiller, G.
    Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra2010Ingår i: Atmospheric Measurement Techniques Discussions, ISSN 1867-8610, E-ISSN 1867-8610, Vol. 3, nr 2, 1707-1742 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine volume mixing ratios (vmr) retrieved from limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). In level 2 (L2) data products of three different retrieval processors, which perform one dimensional (1-D) retrievals, we find significant differences between species' profiles from ascending and descending orbit parts. The relative differences vary systematically with time of the year, latitude, and altitude. In the lower stratosphere their monthly means can reach maxima of 20% for CFC-11, CFC-12, HNO3, H2O, 10% for CH4 and N2O. Relative differences between monthly means of 1-D retrieval results and of the true atmospheric state can be expected to reach half of these percentage values, while relative differences in single vmr profiles might well exceed those numbers. Often there are no physical or chemical reasons for these differences, so they are an indicator for a problem in the data processing. The differences are generally largest at locations where the meridional temperature gradient of the atmosphere is strong. On the contrary, when performing the retrieval with a tomographic two dimensional (2-D) retrieval, L2 products generally do not show these differences. This implies that inhomogeneities in the temperature field, and possibly in the species' fields, which are accounted for in the 2-D algorithm and not in standard 1-D processors, may cause significant deviations in the results. Inclusion of an externally given adequate temperature gradient in the forward model of a 1-D processor helps to reduce the observed differences. However, only the full tomographic approach is suitable to resolve the horizontal inhomogeneities. Implications for the use of the 1-D data, e.g. for validation, are discussed. The dependence of the ascending/descending differences on the observation strategy suggests that this problem is to be expected to affect in general 1-D retrievals of infrared limb sounders, if the line of sight of the instrument has a significant component in the direction of the horizontal temperature variation.

  • 174.
    Kiewiet, Luca
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Université Toulouse III Paul Sabatier.
    Design of the Hold-Down and Release System for the Concur™ Solar Array Wing2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Publikationen är tillgänglig i fulltext från 2018-12-31 08:00
  • 175.
    Kindberg, Peter
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a miniature Gridded ion thruster2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 176.
    Kirkwood, Sheila
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Belova, Evgenia G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Dalin, Peter A.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mihalikova, Maria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Mikhaylova, Daria
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Murtagh, Donal P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Satheesan, K.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Urban, Joachim B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Wolf, Ingemar
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: The importance of nitric oxide2013Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 31, nr 2, 333-347 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic I K indices) is examined. Calibrated PMSE reflectivities for the period May 2006-February 2012 are used from two 52.0/54.5 MHz radars located in Arctic Sweden (68 N, geomagnetic latitude 65 ) and at two different sites in Queen Maud Land, Antarctica (73/72 S, geomagnetic latitudes 62/63 ). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle precipitation, the delayed response can largely be explained by changes in nitric oxide concentrations. Observations of nitric oxide concentration at PMSE heights by the Odin satellite support this hypothesis. Sensitivity to geomagnetic disturbances, including nitric oxide produced during these disturbances, can explain previously reported differences between sites in the auroral zone and those at higher or lower magnetic latitudes. The several-day lifetime of nitric oxide can also explain earlier reported discrepancies between high correlations for average conditions (year-by-year PMSE reflectivities and indices) and low correlations for minute-to-day timescales

  • 177.
    Kloos, Jacob L.
    et al.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Moores, John E.
    York University, Toronto.
    Lemmon, Mark
    Texas A&M University, College Station.
    Kass, David
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Francis, Raymond
    Jet Propulsion Laboratory/Caltech.
    Juarez, Manuel de la Torre
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Zorzano, María Paz
    Centro de Astrobiología (CSIC-INTA), Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    The First Martian Year of Cloud Activity from Mars Science Laboratory (Sol 0 - 800)2016Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 57, nr 5, 1223-1240 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using images from the Navigation Cameras onboard the Mars Science Laboratory rover Curiosity, atmospheric movies were created to monitor the cloud activity over Gale Crater. Over the course of the first 800 sols of the mission, 133 Zenith Movies and 152 Supra-Horizon Movies were acquired which use a mean frame subtraction technique to observe tenuous cloud movement. Moores et al. (2015a) reported on the first 360 sols of observations, representing LS = 150° to 5°, and found that movies up to LS = 184° showed visible cloud features with good contrast while subsequent movies were relatively featureless. With the extension of the observations to a full Martian year, more pronounced seasonal changes were observed. Within the Zenith Movie data set, clouds are observed primarily during LS = 3° - 170°, when the solar flux is diminished and the aphelion cloud belt is present at equatorial latitudes. Clouds observed in the Supra-Horizon Movie data set also exhibit seasonality, with clouds predominantly observed during LS = 72° - 108°. The seasonal occurrence of clouds detected in the atmospheric movies is well correlated with orbital observations of water-ice clouds at similar times from the MCS and MARCI instruments on the MRO spacecraft. The observed clouds are tenuous and on average only make up a few-hundredths of an optical depth, although more opaque clouds are observed in some of the movies. Additionally, estimates of the phase function calculated using water-ice opacity retrievals from MCS are provided to show how Martian clouds scatter sunlight, and thus provide insight into the types of ice crystals that comprise the clouds.

  • 178.
    Kohlbacher, Anton
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a Novel Relative Localization Sensor2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    By enabling coordinated task execution and movement, robotic swarms can achieve efficient exploration or disaster site management. When utilizing Ultra-wideband (UWB) radio technology for ranging, the proposed relative localization sensor can be made lightweight and relatively indifferent to the ambient environment. Infrastructure dependency is eliminated by making the whole sensor fit on a swarm agent, while allowing for a certain amount of positional error. In this thesis, a novel algorithm is implemented in to constrained hardware and compared to a more traditional trilateration approach. Both algorithms utilize Particle Swarm Optimization (PSO) to be more robust towards noise and achieves similar accuracy, but the proposed algorithm can run up to ten times faster. The antenna array which forms the localization sensor weighs only 56g, and achieves around 0.5m RMSE with a 10Hz update rate. Experiments show that the accuracy can be further improved if the rotational bias observed in the UWB devices are compensated for.

  • 179.
    Korablev, Oleg I.
    et al.
    Space Research Institute IKI, Moscow.
    Dobrolensky, Yurii
    Space Research Institute IKI, Moscow.
    Evdokimova, Nadezhda
    Space Research Institute IKI, Moscow.
    Fedorova, Anna A.
    Space Research Institute IKI, Moscow.
    Kuzmin, Ruslan O.
    Space Research Institute IKI, Moscow.
    Mantsevich, Sergei N.
    Space Research Institute IKI, Moscow.
    Cloutis, Edward A.
    The University of Winnipeg.
    Carter, John
    Institut d'Astrophysique Spatiale IAS-CNRS/Université Paris Sud Orsay.
    Poulet, Francois
    Institut d'Astrophysique Spatiale IAS-CNRS/Université Paris Sud Orsay.
    Flahaut, Jessica
    Université Lyon 1, ENS-Lyon, CNRS.
    Griffiths, Andrew
    Mullard Space Science Laboratory, University College London, Dorking.
    Gunn, Matthew
    Department of Physics, Aberystwyth University.
    Schmitz, Nicole
    German Aerospace Center DLR, Köln.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rodianov, Daniil S.
    Space Research Institute IKI, Moscow.
    Vago, Jorge L.
    ESA ESTEC, Noordwijk.
    Stepanov, Alexander V.
    Space Research Institute IKI, Moscow.
    Titov, Andrei Yu.
    Space Research Institute IKI, Moscow.
    Vyazovetsky, Nikita A.
    Space Research Institute IKI, Moscow.
    Trokhimovskiy, Alexander Yu.
    Space Research Institute IKI, Moscow.
    Sapgir, Alexander G.
    Space Research Institute IKI, Moscow.
    Kalinnikov, Yurii K.
    Space Research Institute IKI, Moscow.
    Ivanov, Yurii S.
    Main Astronomical Observatory MAO NASU, Kyiv.
    Shapkin, Alexei A.
    Space Research Institute IKI, Moscow.
    Ivanov, Andrei Yu.
    Space Research Institute IKI, Moscow.
    Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover2017Ingår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, nr 6-7, 542-564 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ∼1° field of view and covers the spectral range between 1.15 and 3.30 μm with a spectral resolution varying from 3.3 nm at 1.15 μm to 28 nm at 3.30 μm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described.

  • 180.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Representation and diurnal variation of upper tropospheric humidity in observations and models2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The role of water vapour is manifold in its climate regulation of the Earth system. Most important of all despite its low concentration, is the role it plays in the upper troposphere. It assumes an important role in its contribution to greenhouse warming by way of its positive feedback effect, amplifying the radiative forcing due to increasing CO2 concentrations. Understanding the variability and distribution is thus important from a climate point of view and critical because the challenges involved in it are far too many. This thesis consists of an introduction and three research articles focusing on the study of upper tropospheric humidity (UTH). The first two articles are on two important sources of UTH data, the radiosondes and satellite data, and the third is associated with climate models, important tools for simulating and reproducing global climate features. The summaries of these three articles are as follows:Radiosondes have been the primary sources for vertical profiles of various atmospheric parameters and are one of the crucial components in numerical weather predictions and satellite validations. However, they are known to have certain issues withmeasurements of humidity in the upper troposphere. The first article highlights the importance of radiosonde humidity corrections by using satellite measurements as the reference. The infrared and microwave measurements from NOAA-17 polar orbiting satellite were used as the reference in this study. Collocated radiosonde measurements from the Atmospheric Radiation Measurement (ARM) campaign were converted into satellite radiances using the ARTS radiative transfer model. The comparisons with satellite measurements were done separately for daytime and nighttime soundings of radiosonde under clear sky conditions. An empirical correction procedure meant to address the mean bias error and solar radiation error was applied to the radiosondes. The empirical correction was found to significantly reduce the dry bias of radiosondes in the upper troposphere. The impact of the correction is prominent over daytime radiosonde measurements on account of the bias removal associated with the solar radiation error.Long term time-series measurements of tropospheric humidity are available from polar orbiting satellites but the measurements from these satellites have been found to be affected by diurnal sampling bias, which is caused by a drift in the orbital height of the satellites, thus changing the local sampling time of the satellites over course of time. This therefore introduces a spurious trend into the time-series data obtained from these satellites. A methodology for the correction of orbital drift error applied on microwave humidity measurements from NOAA and MetOp-A satellites forms the subject of the second article included in this thesis. Climatological diurnal cycles of microwave humidity measurements were obtained from 5 different polar orbiting satellites to infer and thereby correct the diurnal sampling bias in microwave humiditymeasurements. The diurnal cycles were generated separately for the 5 microwave channels. A Monte Carlo error analysis also determines the significance of diurnal amplitudes. The impact of diurnal correction has been evaluated by analyzing the surface channel brightness temperature time-series of NOAA-16 and UTH channel time-series of NOAA-17 satellites. The impact of diurnal correction is greater for the surface channels when compared to the UTH channels due to the larger diurnal cycle amplitudes in the surface channels.Climate models are one of the main tools for the prediction of future climatechange. Most processes associated with water vapour appear in climate models as parameterizations since they are too small-scale or complex to be physically represented in models. Therefore, frequent validation of models against observations is needed to assure their reliability. The third article evaluates the performance of two climate models, in simulating the diurnal cycles of upper tropospheric humidity taking combined microwave humidity measurements from four different satellites as the reference. The comparisons were made over the convective land and oceanic regions over the tropics. The diurnal cycle differences between infrared and microwave observations and the reason for these differences are also analyzed. It is shown that the cloud sensitivity differences in infrared data can shift the diurnal phase relative to microwave data. The models exhibit considerable differences in the diurnal phase and amplitude of UTH as against microwave observations over both land and oceanic regions.

  • 181.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Satellite and radiosonde measurements of atmospheric humidity2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This licentiate thesis is based on two papers which are related to the study ofatmospheric humidity. The first paper mainly focuses on a non linear method forretrieving atmospheric humidity from infrared sounder satellite measurements basedon fuzzy clustering which could potentially improve the retrieval accuracy. The mainaim of this study was to provide a better first guess humidity profile for physicalretrieval algorithms which can further improve retrieval accuracy. This method hasbeen compared against linear and non linear regression retrievals which are the gen-erally used methods to get the first guess profile. The results reveal that the retrievalaccuracy is better for the new method as compared to the conventional methods.Generally, the accuracy of the humidity measurements of radiosonde is poor in theupper troposphere (UT) and is worse for day time measurements due to solar heatingof the humidity sensor. Several methods have been developed to correct the humiditymeasurements of radiosondes in the UT. The second paper presents a detailed analysisof the implications of these corrections and depicts how important they are for satellitevalidation. The corrections have been applied separately for daytime and nighttimeradiosonde measurements and their effects have been quantified by comparing againstthe coinciding satellite measurements in the infrared and microwave spectral rangeused for humidity measurements.

  • 182.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, Viju
    Hadley Centre, UK MetOffice, Exeter, UK.
    Evaluating the diurnal cycle of upper tropospheric humidity in two different climate models using satellite observations2016Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The diurnal cycle of upper tropospheric humidity (UTH) is known to be influenced by such processes as convection and the formation of clouds. These processes need to be parameterized in global climate models. In this study, we evaluate the performance of the climate models CAM-5 and GA-3 in simulating the diurnal cycle of UTH by taking combined microwave measurements from four different polar orbiting satellites as the reference. These comparisons were made over two convective land regions in South America and Africa, and over oceanic regions, in the Atlantic, Indian and West Pacific for the month of January, 2007. In addition to the comparison with microwave data, comparisons with the diurnal cycle generated from IR observations from METEOSAT were done for the African and Atlantic regions. We analyzed how the diurnal cycles from IR and microwave instruments differ, and the reason for these differences. The models exhibit considerable discrepancies in diurnal amplitude and phase relative to the microwave observations, and these discrepancies have different magnitudes over land and ocean. We also confirm that the cloud sensitivity difference is the main reason for the observed differences in the diurnal cycles of IR and microwave UTH.

  • 183.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, Viju O.
    UK Met Office, Exeter.
    Miloshevich, Larry M.
    Milo Scientific LLC, Lafayette, Colorado.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    On the importance of Vaisala RS92 radiosonde humidity corrections for a better agreement between measured and modeled satellite radiances2012Ingår i: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 29, nr 2, 248-259 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study has been carried out to assess the importance of radiosonde corrections in improving the agreement between satellite and radiosonde measurements of upper-tropospheric humidity. Infrared [High Resolution Infrared Radiation Sounder (HIRS)-12] and microwave [Advanced Microwave Sounding Unit (AMSU)-18] measurements from the NOAA-17 satellite were used for this purpose. The agreement was assessed by comparing the satellite measurements against simulated measurements using collocated radiosonde profiles of the Atmospheric Radiation Measurement (ARM) Program undertaken at tropical and midlatitude sites. The Atmospheric Radiative Transfer Simulator (ARTS) was used to simulate the satellite radiances. The comparisons have been done under clear-sky conditions, separately for daytime and nighttime soundings. Only Vaisala RS92 radiosonde sensors were used and an empirical correction (EC) was applied to the radiosonde measurements. The EC includes correction for mean calibration bias and for solar radiation error, and it removes radiosonde bias relative to three instruments of known accuracy. For the nighttime dataset, the EC significantly reduces the bias from 0.63 to −0.10 K in AMSU-18 and from 1.26 to 0.35 K in HIRS-12. The EC has an even greater impact on the daytime dataset with a bias reduction from 2.38 to 0.28 K in AMSU-18 and from 2.51 to 0.59 K in HIRS-12. The present study promises a more accurate approach in future radiosonde-based studies in the upper troposphere.

  • 184.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Correcting diurnal cycle aliasing in satellite microwave humidity sounder measurements2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 1, 101-113 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microwave humidity measurements from polar orbiting satellites are affected by diurnal sampling biases which are caused by changes in the local observation time of the satellites. The long term data records available from these satellites thus have spurious trends, which must be corrected. Diurnal cycles of the microwave measurements have been constructed by combining data over the period 2001--2010 from five different satellite platforms (NOAA-15, -16, -17, -18, and MetOpA). This climatological diurnal cycle has been used to deduce and correct the diurnal sampling bias in AMSU-B and MHS measurements. Diurnal amplitudes for channels which are sensitive to surface temperature variations show a sharp land-sea contrast with the amplitudes exceeding 10 K for land regions, but less than one Kelvin for oceanic regions. The humidity channels sensitive to the upper and middle troposphere exhibit a seasonal variation with large diurnal amplitudes over convective land regions (often above 3 K) in comparison to oceanic regions. The diurnal peak times of these channels over land occur in the early mornings. The diurnal sampling bias correction has a greater impact over land regions when compared to oceanic regions due to the large diurnal amplitudes over land. The diurnal cycle of humidity generated as a part of this study could be used to evaluate diurnal cycles in climate models.

  • 185.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Thapliyal, Pradeep
    Space Applications Centre, ISRO, Ahmedabad.
    Shukla, Munn
    Space Applications Centre, ISRO, Ahmedabad.
    Pal, Pradip
    Space Applications Centre, ISRO, Ahmedabad.
    Joshi, Prakash
    Space Applications Centre, ISRO, Ahmedabad.
    Ranganath, Navalgund
    Space Applications Centre, ISRO, Ahmedabad.
    A new technique for temperature and humidity profile retrieval from infrared sounder observations using adaptive neuro-fuzzy inference system2010Ingår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 48, nr 4, 1650-1659 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accuracy of the atmospheric profiles of temperature and humidity, retrieved from infrared sounder observations using physical retrieval algorithm, depend primarily on the quality of the first guess profiles. In the past, forecasts from the numerical weather prediction models were extensively used as the first guess. During past few years, the first guess for physical retrieval is being estimated using regression techniques from sounder observations. In the present study, a new non-linear technique has been described to improve the first guess using simulated infrared brightness temperatures for GOES-12 Sounder channels. The present technique uses fuzzy logic and data clustering to establish a relationship between simulated sounder observations and atmospheric profiles. This relationship is further strengthened using Adaptive Neuro-Fuzzy Inference System (ANFIS) by fine-tuning the existing fuzzy rule base. The results of ANFIS retrieval have been compared with the non-linear (polynomial) regression retrieval. It has been found that ANFIS is more robust and shows remarkable improvement as it reduces RMS error by 20% in humidity profiles retrieval compared to the non-linear regression technique. In addition, it has been shown that the ANFIS technique has an added advantage of its global application without any need for training data classification that is required in the regression techniques.

  • 186.
    Kudaravalli, Venkata Narayana Chowdary
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design and fabrication of test-bed for testing attitude determination of spin stablilized spacecraft.2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

     Attitude determination for a spin stabilized satellite is calibrated. A mock spacecraft and a spin simulation test bed are designed and developed. Spin simulation testbed which provides position data is used to acquire true position data. The data from the simulator test bed is used as reference for the sensor data to estimate the error in position of sensor data. Two vector method attitude solutions are used here for attaining the estimated position. Two vectors used for attitude determination are magnetic field vector and sun sensor vector. Calibration of accuracy for sensors is main goal, which is attained by calculating error by comparing the estimated position with true position.

  • 187.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Damoah, R.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Bacak, A.
    School of Earth, Atmospheric and Environmental Sciences, University of Manchester.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Characterising aerosol transport into the Canadian high Arctic using aerosol mass spectrometry and Lagrangian modelling2010Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 21, 10489-10502 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the analysis of measurements made using an aerosol mass spectrometer (AMS; Aerodyne Research Inc.) that was installed in the Polar Environment Atmospheric Research Laboratory (PEARL) in summer 2006. PEARL is located in the Canadian high Arctic at 610 m above sea level on Ellesmere Island (80° N 86° W). PEARL is unique for its remote location in the Arctic and because most of the time it is situated within the free troposphere. It is, therefore, well suited as a receptor site to study the long-range tropospheric transport of pollutants into the Arctic. Some information about the successful year-round operation of an AMS at a high Arctic site such as PEARL will be reported here, together with design considerations for reliable sampling under harsh low-temperature conditions. Computational fluid dynamics calculations were made to ensure that sample integrity was maintained while sampling air at temperatures that average 40 °C in the winter and can be as low as 55 °C. Selected AMS measurements of aerosol mass concentration, size and chemical composition recorded during the months of August, September and October 2006 will be reported. The air temperature was raised to about 20 deg;C during sampling, but the short residence time in the inlet system (∼25 s) ensured that less than 10% of semivolatiles such as ammonium nitrate were lost. During this period, sulfate was, at most times, the predominant aerosol component with on average 0.115 μg-3 (detection limit 0.003mg-3). The second most abundant component was undifferentiated organic aerosol, with on average 0.11 Î1/4g mg3 (detection limit 0.04 I1/4g mg3). The nitrate component, which averaged 0.007 mg-3, was above its detection limit (0.002 Î1/4g mg3), whereas the ammonium ion had an apparent average concentration of 0.02 g mg-3, which was approximately equal to its detection limit. A few episodes, having increased mass concentrations and lasting from several hours to several days, are apparent in the data. These were investigated further using a statistical analysis to determine their common characteristics. High correlations among some of the components arriving during the short-term episodes provide evidence for common sources. Lagrangian methods were also used to identify the source regions for some of the episodes. In all cases, these coincided with the arrival of air that had contacted the surface at latitudes below about 60° N. Most of these lower-latitude footprints were on land, but sulfate emissions from shipping in the Atlantic were also detected. The Lagrangian results demonstrate that there is direct transport of polluted air into the high Arctic (up to 80° N) from latitudes down to 40° N on a time scale of 2-3 weeks. The polluted air originates in a wide variety of industrial, resource extraction and petroleum-related activity as well as from large population centres

  • 188.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Earle, M.E.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Khalizov, A.F.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets2011Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, nr 6, 2853-2861 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 Î1/4m. Temperature-and size-dependent values of volume-and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 Î1/4m. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered

  • 189.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Gultepe, Ismail
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Ice Fog and Light Snow Measurements Using a High-Resolution Camera System2016Ingår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, nr 9, 3049-3064 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ice fog, diamond dust, and light snow usually form over extremely cold weather conditions, and they affect both visibility and Earth’s radiative energy budget. Prediction of these hydrometeors using models is difficult because of limited knowledge of the microphysical properties at the small size ranges due to measurement issues. These phenomena need to be better represented in forecast and climate models; therefore, in addition to remote sensing accurate measurements using ground-based instrumentation are required. An imaging instrument, aimed at measuring ice fog and light snow particles, has been built and is presented here. The ice crystal imaging (ICI) probe samples ice particles into a vertical, tapered inlet with an inlet flow rate of 11 L min−1. A laser beam across the vertical air flow containing the ice crystals allows for their detection by a photodetector collecting the scattered light. Detected particles are then imaged with high optical resolution. An illuminating LED flash and image capturing are triggered by the photodetector. In this work, ICI measurements collected during the fog remote sensing and modeling (FRAM) project, which took place during Winter of 2010–2011 in Yellowknife, NWT, Canada, are summarized and challenges related to measuring small ice particles are described. The majority of ice particles during the 2-month-long campaign had sizes between 300 and 800 μm. During ice fog events the size distribution measured had a lower mode diameter of 300 μm compared to the overall campaign average with mode at 500 μm.

  • 190.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus2016Ingår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, nr 9, 3065-3084 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cirrus clouds reflect incoming solar radiation, creating a cooling effect. At the same time, these clouds absorb the infrared radiation from the Earth, creating a greenhouse effect. The net effect, crucial for radiative transfer, depends on the cirrus microphysical properties, such as particle size distributions and particle shapes. Knowledge of these cloud properties is also needed for calibrating and validating passive and active remote sensors. Ice particles of sizes below 100 µm are inherently difficult to measure with aircraft-mounted probes due to issues with resolution, sizing, and size-dependent sampling volume. Furthermore, artefacts are produced by shattering of particles on the leading surfaces of the aircraft probes when particles several hundred microns or larger are present. Here, we report on a series of balloon-borne in situ measurements that were carried out at a high-latitude location, Kiruna in northern Sweden (68N 21E). The method used here avoids these issues experienced with the aircraft probes. Furthermore, with a balloon-borne instrument, data are collected as vertical profiles, more useful for calibrating or evaluating remote sensing measurements than data collected along horizontal traverses. Particles are collected on an oil-coated film at a sampling speed given directly by the ascending rate of the balloon, 4 m s−1. The collecting film is advanced uniformly inside the instrument so that an always unused section of the film is exposed to ice particles, which are measured by imaging shortly after sampling. The high optical resolution of about 4 µm together with a pixel resolution of 1.65 µm allows particle detection at sizes of 10 µm and larger. For particles that are 20 µm (12 pixel) in size or larger, the shape can be recognized. The sampling volume, 130 cm3 s−1, is well defined and independent of particle size. With the encountered number concentrations of between 4 and 400 L−1, this required about 90- to 4-s sampling times to determine particle size distributions of cloud layers. Depending on how ice particles vary through the cloud, several layers per cloud with relatively uniform properties have been analysed. Preliminary results of the balloon campaign, targeting upper tropospheric, cold cirrus clouds, are presented here. Ice particles in these clouds were predominantly very small, with a median size of measured particles of around 50 µm and about 80 % of all particles below 100 µm in size. The properties of the particle size distributions at temperatures between −36 and −67 °C have been studied, as well as particle areas, extinction coefficients, and their shapes (area ratios). Gamma and log-normal distribution functions could be fitted to all measured particle size distributions achieving very good correlation with coefficients R of up to 0.95. Each distribution features one distinct mode. With decreasing temperature, the mode diameter decreases exponentially, whereas the total number concentration increases by two orders of magnitude with decreasing temperature in the same range. The high concentrations at cold temperatures also caused larger extinction coefficients, directly determined from cross-sectional areas of single ice particles, than at warmer temperatures. The mass of particles has been estimated from area and size. Ice water content (IWC) and effective diameters are then determined from the data. IWC did vary only between 1 × 10−3 and 5 × 10−3 g m−3 at temperatures below −40 °C and did not show a clear temperature trend. These measurements are part of an ongoing study.

  • 191.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    NCAR, Boulder, Colorado.
    Vertical distributions of small cirrus cloud particles from balloon-borne in-situ measurements: Oral presentation2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Thin and cold ice clouds are important for the radiative budget, yet they are difficult to measure. They are often high in the troposphere where they reflect incoming sunlight, creating a cooling effect. At the same time these clouds absorb longwave radiation from Earth, creating a greenhouse effect. Knowledge of the net effect is crucial and depends on the microphysical properties of the clouds, which at these altitudes and temperatures are often composed of small particles of 100 μm or less in size. Most of in-situ data reported in the literature have been sampled with aircraft probes, which have known issues with such small particles due to sizing and shattering prob- lems, in addition to having also a small and size-dependent sampling volume for these particles.A series of balloon-borne in-situ measurements, currently being carried out from a high-latitude location in north- ern Sweden (Kiruna, 68N 21E), combined with previous balloon-borne measurements from other locations, are used to study properties of small cloud ice particles at a variety of temperatures and altitudes. Among other prop- erties, size distributions and concentrations are analysed as a function of height within the cloud layer. Results are compared to literature data from aircraft probes to shed more light on the uncertainties related to the difficulties of these probes in measuring small particles.

  • 192.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Balloon-Borne Measurements of Ice Particle Shape and Ice Water Content in the Upper Troposphere over Northern Sweden2013Ingår i: 21st ESA Symposium: ESA Symposium on European Rocket and Balloon Programmes and Related Research 2013, 9–13 June 2013, Noordwijk: European Space Agency, ESA , 2013, 93-97 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ice clouds play an important role in the energy budget of the atmosphere. They are at high altitudes, absorb long-wave radiation from below and, as they are cold, emit little infrared radiation. This greenhouse effect warms the Earth-atmosphere system. On the other hand, ice clouds have a cooling effect by reflecting incoming solar short wave radiation. The net effect is crucial for the atmosphere, but will depend highly on the cloud’s horizontal extent, vertical position, ice water content (IWC), and ice particle microphysical properties such as size and shape. Targeting these upper-tropospheric, cold ice clouds, a series of in-situ balloon-borne experiments has been started at Kiruna, Sweden, which is located at 68°N. Fewer mea- surements exist at these high latitudes compared to mid- or tropical latitudes. Also temperatures in the upper troposphere can be around -60 °C, a temperature range under-represented in available in-situ data. Experiments are launched from Esrange Space Center. Ice particles are collected with a balloon-borne replicator and also imaged in-situ, and measurements are complemented by a radiosonde added to the instrument. Particle shape and size as well as IWC are determined from the replicas and images. The data are analysed to reveal relationships between IWC and other measurements such as temperature and volume extinction coefficient. Such relationships can be used for validation and improvement of satellite retrievals of IWC from, for example, thin cirrus measurements with satellite-borne lidar, such as on the future EarthCARE mission.

  • 193.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    In-situ ice particle measurements over northern Sweden2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    ce clouds play an important role in the energy budget of the atmosphere. They are at high altitudes, absorb longwave radiation from below and, as they are cold, emit little infrared radiation. This greenhouse effect warms the Earth-atmosphere system. On the other hand, ice clouds have a cooling effect by reflecting incoming solar short wave radiation. The net effect is crucial for the atmosphere, but will depend highly on the cloud’s horizontal extent, vertical position, ice water content (IWC), and ice particle microphysical properties such as size and shape. A series of in-situ balloon measurements has been started at Kiruna, Sweden, which is located at 68°N. Fewer in- situ ice cloud measurements exist at these high latitudes compared to mid- or tropical latitudes. Also temperatures in the upper troposphere can be around -60 °C, a temperature range under-represented in available in-situ data. Ice particles are collected with a balloon-borne replicator launched from Esrange Space Center (near Kiruna, Sweden). Measurements are complemented by a radiosonde added to the instrument. The shape and size as well as IWC are determined from the replicas. The data are analyzed to reveal relationships between IWC and other measurements such as temperature and volume extinction coefficient. Such relationships can be used for validation and improvement of satellite retrievals of IWC from, for example, thin cirrus measurements with satellite-borne lidar.

  • 194.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wolf, Veronika
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Völger, Peter
    The Swedish Institute of Space Physics (IRF).
    Stanev, Marin
    Stockholm University, Department of Meteorology (MISU).
    Gumbel, Jörg
    Stockholm University, Department of Meteorology (MISU).
    Comparison of In-Situ Balloon-Borne and Lidar Measurement of Cirrus Clouds2017Ingår i: Proceedings of the 23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research, Noordwijk, The Netherlands, 2017, A-091kuhnKonferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A series of in-situ balloon-borne experiments con- ducted at Kiruna, Sweden (68°N), is studying upper- tropospheric, cold ice clouds in arctic latitudes. Ex- periments are launched from Esrange Space Center and collect ice particles with an in-situ imaging instrument. One of the aims with these measurements is to improve satellite remote sensing of cold ice clouds. Such clouds can be observed by lidar. Therefore, when possible, concurrent ground-based lidar measurements have been carried out with two available lidar systems to accom- pany the balloon-borne measurements. The Esrange lidar is located at Esrange Space Center, approximately 500 m from the in-situ launch site on the balloon pad; the IRF lidar is located about 29 km to the west of Esrange Space Center (operated by the Swedish Institute of Space Physics, IRF). Here we present results from these lidar measurements and compare them to ice particle proper- ties determined during the in-situ measurements. 

  • 195.
    Kumar, Rajesh
    et al.
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Ramesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Singh, Atar
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sam, Lydia
    Department of Environmental Science, Sharda University, Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Randhawa, Surjeet Singh
    State Council for Science, Technology. & Environment, Shimla.
    Gupta, Akhilesh
    Department of Science and Technology, Technology Bhavan, New Delhi.
    Development of a Glacio-hydrological Model for Discharge and Mass Balance Reconstruction2016Ingår i: Water resources management, ISSN 0920-4741, E-ISSN 1573-1650, Vol. 30, nr 10, 3475-3492 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reconstruction of glacio-hydrological records for the data deficient Himalayan catchments is needed in order to study the past and future water availability. The study provides outcomes of a glacio-hydrological model based on the degree-day approach. The model simulates the discharge and mass balance for glacierised Shaune Garang catchment. The degree-day factors for different land covers, used in the model, were estimated using daily stake measurements on Shaune Garang glacier and they were found to be varying between 2.6 ± 0.4 and 9.3 ± 0.3 mm °C−1day−1. The model is validated using observed discharge during ablation season of 2014 with coefficient of determination (R2) 0.90 and root mean square error (RMSE) 1.05 m3 sec−1. The model is used to simulate discharge from 1985 to 2008 and mass balance from 2001 to 2008. The model results show significant contribution of seasonal snow and ice melt in total discharge of the catchment, especially during summer. We observe the maximum discharge in July having maximum contribution from snow and ice melt. The annual melt season discharge shows following a decreasing trend in the simulation period. The reconstructed mass balance shows mass loss of 0.89 m we per year between 2001 and 2008 with slight mass gain during 2000/01 and 2004/05 hydrological years.

  • 196.
    Kunicka, Beata Iwona
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Spacecraft dynamic analysis and correlation with test results: Shock environment analysis of LISA Pathfinder at VESTA test bed2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite.

    In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS).

    The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity,  and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation.  From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB.

    Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test.

    In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.

  • 197.
    Lahoz, William A.
    et al.
    University of Reading, Data assimililation research centre.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Legras, Bernard
    Laboratoire de Météorologie Dynamique, Paris.
    The COST 723 Action2007Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr S2, 99-108 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An overview is provided of the COST 723 Action, Data Exploitation and Modelling of the Upper Troposphere and Lower Stratosphere. The three working groups are introduced and a summary of Action activities within them is provided. The achievements of the Action are: three international workshops; the LAUTLOS humidity measurement campaign; dedicated meetings to discuss the quality of upper troposphere/lower stratosphere ozone and humidity measurements; two journal special issues; more than 90 papers in the peer-reviewed literature; one international summer school; and a successor COST Action which builds on COST 723. The recommendations made are: for COST to continue to support the short-term scientific missions instrument, as they are perceived to be value for money; to encourage the use of COST money to increase links between COST Actions and other scientific communities; and for the COST secretariat to recommend that Actions consider a summer school instead of a final workshop or meeting.

  • 198.
    Lanza, Nina L.
    et al.
    Los Alamos National Laboratory.
    Wiens, Roger C.
    Los Alamos National Laboratory, Space Remote Sensing, Los Alamos National Laboratory, Los Alamos, International Space and Response Division, Los Alamos National Laboratory.
    Arvidson, Ray E.
    Washington University, St. Louis.
    Clark, Benton C.
    Space Science Institute, Boulder, Colorado, Space Science Institute.
    Fischer, W.W.
    California Institute of Technology, Pasadena.
    Gellert, Ralf
    University of Guelph, Ontario, University of Guelph, Department of Physics, University of Guelph, Ontario.
    Grotzinger, John P.
    California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology, Caltech, Pasadena, Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Hurowitz, J.A.
    Department of Geosciences, Stony Brook University, Stony Brook University, NY, Department of Geosciences, State University of New York, Stony Brook.
    McLennan, S.M.
    Department of Geosciences, Stony Brook University, Stony Brook University, NY, Department of Geosciences, State University of New York, Stony Brook, The State University of New York, Stony Brook.
    Morris, R.V.
    NASA Johnson Space Center, NASA Johnson Space Center, Houston, Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston.
    Rice, M.S.
    California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology.
    III, J.F. Bell
    Arizona State University, School of Earth and Space Exploration, Arizona State University, School of Earth and Space Exploration, Arizona State University, Tempe.
    Berger, Jeff A.
    University of Western Ontario, London.
    Blaney, Diana L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Bridges, Nathan T.
    Johns Hopkins University Applied Physics Laboratory, Laurel, Applied Physics Laboratory, Laurel, Maryland.
    Calef, Fred
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Jet Propulsion Laboratory.
    Campbell, J.L.
    Department of Physics, University of Guelph, Ontario, University of Guelph, Ontario.
    Clegg, S.M.
    Los Alamos National Laboratory, Chemistry Division, Los Alamos National Laboratory.
    Cousin, A.
    Los Alamos National Laboratory, Chemistry Division, Los Alamos National Laboratory.
    Edgett, Kenneth S.
    Malin Space Science Systems, San Diego, Malin Space Science Systems.
    Fabre, Cécile
    Université de Lorraine, Nancy.
    Fisk, M.R.
    Oregon State University, Corvallis.
    Forni, Olivier
    IRAP/CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse, Université de Toulouse, UPS-OMP, IRAP, Institut de Recherche en Astophysique et Planetologie (IRAP), Universite' Paul Sabatier, Toulouse, IRAP, CNRS/UPS, Toulouse.
    Frydenvang, J.
    Niels Bohr Institute, University of Copenhagen.
    Hardy, K.R.
    U.S. Naval Academy, Annapolis.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars2016Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, nr 14, 7398-7407 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Curiosity rover observed high Mn abundances (>25wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day

  • 199.
    Lanza, N.L.
    et al.
    Los Alamos National Laboratory.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Arvidson, R.E.
    Washington University, St. Louis.
    Clark, B.C.
    Space Science Institute, Boulder, Colorado.
    Fischer, W.W.
    California Institute of Technology, Pasadena.
    Gellert, R.
    University of Guelph, Ontario.
    Grotzinger, J.P.
    California Institute of Technology, Pasadena.
    Hurowitz, J.A.
    Stony Brook University, NY.
    McLennan, S.M.
    Stony Brook University, NY.
    Morris, R.V.
    NASA Johnson Space Center, Houston.
    Rice, M.S.
    Western Washington University, Bellingham.
    III, J.F. Bell
    Arizona State University.
    Berger, J.A.
    University of Western Ontario, London.
    Blaney, D.L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Blank, J.G.
    NASA Ames, Blue Marble Space Institute of Science, Seattle.
    Bridges, N.T.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    III, F. Calef
    Jet Propulsion Laboratory.
    Campbell, J.L.
    University of Guelph, Ontario.
    Clegg, S.M.
    Los Alamos National Laboratory.
    Cousin, A.
    Los Alamos National Laboratory.
    Edgett, K.S.
    Malin Space Science Systems.
    Fabre, C.
    Université de Lorraine, Nancy.
    Fisk, M.R.
    Oregon State University, Corvallis.
    Forni, O.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Frydenvang, J.
    Niels Bohr Institute, University of Copenhagen.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, M.-P.
    Instituto Nacional de Técnica Aeroespacial, Madrid.
    Oxidation of manganese at Kimberley, Gale Crater: More free oxygen in Mars’ past?2015Konferensbidrag (Refereegranskat)
  • 200.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A note on modelling of the oxygen spectral cross-section in the Atmospheric Radiative Transfer Simulator – Zeeman effect combined with line mixing in the Earth’s atmosphere2014Ingår i: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 35, nr 15, 5845-5853 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new module to the Atmospheric Radiative Transfer Simulator is presented that models the strong oxygen spectral band at 60 GHz. The module handles the line mixing effect and works with or without additionally calculating the Zeeman effect. It is shown how the module may be internally reduced to calculations of the Zeeman effect at higher altitudes, and to calculations of the line mixing effect at lower altitudes. The article ends with a short discussion on what is being done to validate the module, and what may be done to refine the theoretical description of line mixing in the simulator.

1234567 151 - 200 av 320
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf