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  • 1. Achtert, P.
    et al.
    Brooks, I. M.
    Brooks, B. J.
    Moat, B. I.
    Prytherch, J.
    Persson, P. O. G.
    Tjernstrom, M.
    Measurement of wind profiles by motion-stabilised ship-borne Doppler lidar2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 11, 4993-5007 p.Article in journal (Refereed)
    Abstract [en]

    Three months of Doppler lidar wind measurements were obtained during the Arctic Cloud Summer Experiment on the icebreaker Oden during the summer of 2014. Such ship-borne Doppler measurements require active stabilisation to remove the effects of ship motion. We demonstrate that the combination of a commercial Doppler lidar with a custom-made motion-stabilisation platform enables the retrieval of wind profiles in the Arctic atmospheric boundary layer during both cruising and ice-breaking with statistical uncertainties comparable to land-based measurements. This held true particularly within the atmospheric boundary layer even though the overall aerosol load was very low. Motion stabilisation was successful for high wind speeds in open water and the resulting wave conditions. It allows for the retrieval of vertical winds with a random error below 0.2 ms(-1). The comparison of lidar-measured wind and radio soundings gives a mean bias of 0.3 ms(-1) (2 degrees) and a mean standard deviation of 1.1 ms(-1) (12 degrees) for wind speed (wind direction). The agreement for wind direction degrades with height. The combination of a motion-stabilised platform with a low-maintenance autonomous Doppler lidar has the potential to enable continuous long-term high-resolution ship-based wind profile measurements over the oceans.

  • 2.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pure rotational-Raman channels of the Esrange lidar for temperature and particle extinction measurements in the troposphere and lower stratosphere2013In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 6, no 1, 91-98 p.Article in journal (Refereed)
    Abstract [en]

    The Department of Meteorology at Stockholm University operates the Esrange Rayleigh/Raman lidar at Esrange(68° N, 21° E) near the Swedish city of Kiruna. This paper describes the design and first measurements of the newpure rotational-Raman channel of the Esrange lidar. The Esrange lidar uses a pulsed Nd:YAG solid-state laser operating at 532 nm as light source with a repetition rate of 20 Hz and a pulse energy of 350 mJ. The minimum vertical resolution is 150m and the integration time for one profile is 5000 shots. The newly implemented channel allows for measurements of atmospheric temperature at altitudes below 35 km and is currently optimized for temperature measurements between 180 and 200 K. This corresponds to conditions in the lower Arctic stratosphere during winter. In addition to the temperature measurements, the aerosol extinction coefficientand the aerosol backscatter coefficient at 532 nm can be measured in dependently. Our filter-based design minimizes the systematic error in the obtained temperature profile to less than 0.51 K. By combining rotational-Raman measurements (5–35 km height) and the integration technique (30–80 kmheight), the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. With the improved setup, the system can be used to validate current lidar-based polar stratospheric cloud classification schemes. The new capability of the instrument measuring temperature and aerosol extinction furthermore enables studies of the thermal structure and variability of the upper troposphere/lower stratosphere. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature profiles in the troposphere, stratosphere, and mesosphere, as well as aerosols extinction in the troposphere and lower stratospherewith daylight capability.

  • 3.
    Baron, P.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Urban, J.
    Chalmers University of Technology.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Möller, J.
    Chalmers University of Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dupuy, E.
    Sato, T.O,
    Ochiai, Satoshi
    National Institute of Information and Communication Technology, Tokyo.
    Suzuk, K.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Nishibori, T.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    Sato, R.
    Takayanagi, M.
    Murayama, Y.
    Shiotani, M.
    Research Institute for Sustainable Humanosphere, Kyoto University.
    Kasai, Y.
    The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)2011In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 4, 2105-2124 p.Article in journal (Refereed)
    Abstract [en]

    This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows.

  • 4. Bennartz, Ralf
    et al.
    Hoschen, Heidrun
    Picard, Bruno
    Schroder, Marc
    Stengel, Martin
    Sus, Oliver
    Bojkov, Bojan
    Casadio, Stefano
    Diedrich, Hannes
    Eliasson, Salomon
    SMHI, Research Department, Atmospheric remote sensing.
    Fell, Frank
    Fischer, Jurgen
    Hollmann, Rainer
    Preusker, Rene
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    An intercalibrated dataset of total column water vapour and wet tropospheric correction based on MWR on board ERS-1, ERS-2, and Envisat2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 4, 1387-1402 p.Article in journal (Refereed)
  • 5.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Defer, E.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Evans, F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eliasson, Salomon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Erikssson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Jimenez, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Prigent, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Crewell, S.
    Institute for Geophysics and Meteorology, University of Cologne.
    kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Bennartz, R.
    Atmospheric and Oceanic Sciences, University of Wisconsin.
    Gasiewski, A.J.
    NOAA-CU Center for Environmental Technology (CET), Department of Electrical and Computer Engineering, University of Colorado at Boulder.
    Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 82012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 7, 1529-1549 p.Article in journal (Refereed)
    Abstract [en]

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  • 6.
    Carlund, Thomas
    et al.
    SMHI, Core Services.
    Kouremeti, Natalia
    Kazadzis, Stelios
    Grobner, Julian
    Aerosol optical depth determination in the UV using a four-channel precision filter radiometer2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 3, 905-923 p.Article in journal (Refereed)
  • 7.
    Chauhan, Swarup
    et al.
    Forschungszentrum Karlsruhe.
    Höpfner, M.
    Stiller, G.P.
    Clarmann, T. von
    Funke, B.
    Glatthor, N.
    Grabowski, U.
    Linden, A.
    Kellmann, S.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Steck, T.
    Fischer, H.
    Froidevaux, L.
    Lambert, A.
    Santee, M. L.
    Schwartz, M.
    Read, W.G.
    Livesey, N.
    MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O3, HNO3, N2O, H2O and relative humidity over ice: retrievals and comparison to MLS2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, no 2, 337-353 p.Article in journal (Refereed)
    Abstract [en]

    During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

  • 8.
    Engström, J. E.
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information2011In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 4, no 8, 1553-1566 p.Article in journal (Refereed)
    Abstract [en]

    The presented filter-based optical method for determination of soot (light absorbing carbon or Black Carbon, BC) can be implemented in the field under primitive conditions and at low cost. This enables researchers with small economical means to perform monitoring at remote locations, especially in the Asia where it is much needed. One concern when applying filter-based optical measurements of BC is that they suffer from systematic errors due to the light scattering of non-absorbing particles co-deposited on the filter, such as inorganic salts and mineral dust. In addition to an optical correction of the non-absorbing material this study provides a protocol for correction of light scattering based on the chemical quantification of the material, which is a novelty. A newly designed photometer was implemented to measure light transmission on particle accumulating filters, which includes an additional sensor recording backscattered light. The choice of polycarbonate membrane filters avoided high chemical blank values and reduced errors associated with length of the light path through the filter. Two protocols for corrections were applied to aerosol samples collected at the Maldives Climate Observatory Hanimaadhoo during episodes with either continentally influenced air from the Indian/Arabian subcontinents (winter season) or pristine air from the Southern Indian Ocean (summer monsoon). The two ways of correction (optical and chemical) lowered the particle light absorption of BC by 63 to 61 %, respectively, for data from the Arabian Sea sourced group, resulting in median BC absorption coefficients of 4.2 and 3.5 Mm(-1). Corresponding values for the South Indian Ocean data were 69 and 97% (0.38 and 0.02 Mm(-1)). A comparison with other studies in the area indicated an overestimation of their BC levels, by up to two orders of magnitude. This raises the necessity for chemical correction protocols on optical filter-based determinations of BC, before even the sign on the radiative forcing based on their effects can be assessed.

  • 9.
    Eriksson, Patrick E J
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    On the microwave optical properties of randomly oriented ice hydrometeors2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 5, 1913-1933 p.Article in journal (Refereed)
    Abstract [en]

    Microwave remote sensing is important for observing the mass of ice hydrometeors. One of the main error sources of microwave ice mass retrievals is that approximations around the shape of the particles are unavoidable. One common approach to represent particles of irregular shape is the soft particle approximation (SPA). We show that it is possible to define a SPA that mimics mean optical particles of available reference data over narrow frequency ranges, considering a single observation technique at the time, but that SPA does not work in a broader context. Most critically, the required air fraction varies with frequency and application, as well as with particle size. In addition, the air fraction matching established density parameterisations results in far too soft particles, at least for frequencies above 90 GHz. That is, alternatives to SPA must be found. One alternative was recently presented by Geer and Baordo (2014). They used a subset of the same reference data and simply selected as "shape model" the particle type giving the best overall agreement with observations. We present a way to perform the same selection of a representative particle shape but without involving assumptions on particle size distribution and actual ice mass contents. Only an assumption on the occurrence frequency of different particle shapes is still required. Our analysis leads to the same selection of representative shape as found by Geer and Baordo (2014). In addition, we show that the selected particle shape has the desired properties at higher frequencies as well as for radar applications. Finally, we demonstrate that in this context the assumption on particle shape is likely less critical when using mass equivalent diameter to characterise particle size compared to using maximum dimension, but a better understanding of the variability of size distributions is required to fully characterise the advantage. Further advancements on these subjects are presently difficult to achieve due to a lack of reference data. One main problem is that most available databases of precalculated optical properties assume completely random particle orientation, while for certain conditions a horizontal alignment is expected. In addition, the only database covering frequencies above 340 GHz has a poor representation of absorption as it is based on outdated refractive index data as well as only covering particles having a maximum dimension below 2 mm and a single temperature

  • 10.
    Eriksson, Patrick
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Rydberg, B.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    On cloud ice induced absorption and polarisation effects in microwave limb sounding2011In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 4, no 6, 1305-1318 p.Article in journal (Refereed)
    Abstract [en]

    Microwave limb sounding in the presence of ice clouds was studied by detailed simulations, where clouds and other atmospheric variables varied in three dimensions and the full polarisation state was considered. Scattering particles were assumed to be horizontally aligned oblate spheroids with a size distribution parameterized in terms of temperature and ice water content. A general finding was that particle absorption is significant for limb sounding, which is in contrast to the down-looking case, where it is usually insignificant. Another general finding was that single scattering can be assumed for cloud optical paths below about 0.1, which is thus an important threshold with respect to the complexity and accuracy of retrieval algorithms. The representation of particle sizes during the retrieval is also discussed. Concerning polarisation, specific findings were as follows: Firstly, no significant degree of circular polarisation was found for the considered particle type. Secondly, for the +/- 45 degrees polarisation components, differences of up to 4 K in brightness temperature were found, but differences were much smaller when single scattering conditions applied. Thirdly, the vertically polarised component has the smallest cloud extinction. An important goal of the study was to derive recommendations for future limb sounding instruments, particularly concerning their polarisation setup. If ice water content is among the retrieval targets (and not just trace gas mixing ratios), then the simulations show that it should be best to observe any of the +/- 45 degrees and circularly polarised components. These pairs of orthogonal components also make it easier to combine information measured from different positions and with different polarisations

  • 11. Hamacher-Barth, E.
    et al.
    Jansson, K.
    Leck, C.
    A method for sizing submicrometer particles in air collected on Formvar films and imaged by scanning electron microscope2013In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 6, no 12, 3459-3475 p.Article in journal (Refereed)
    Abstract [en]

    A method was developed to systematically investigate individual aerosol particles collected onto a polyvinyl formal (Formvar)-coated copper grid with scanning electron microscopy. At very mild conditions with a low accelerating voltage of 2 kV and Gentle Beam mode aerosol particles down to 20 nm in diameter can be observed. Subsequent processing of the images with digital image analysis provides size resolved and morphological information (elongation, circularity) on the aerosol particle population. Polystyrene nanospheres in the expected size range of the ambient aerosol particles (20–900 nm in diameter) were used to confirm the accuracy of sizing and determination of morphological parameters. The relative standard deviation of the diameters of the spheres was better than ±10% for sizes larger than 40 nm and ±18% for 21 nm particles compared to the manufacturer's certificate. 

    Atmospheric particles were collected during an icebreaker expedition to the high Arctic (north of 80°) in the summer of 2008. Two samples collected during two different meteorological regimes were analyzed. Their size distributions were compared with simultaneously collected size distributions from a Twin Differential Mobility Particle Sizer, which confirmed that a representative fraction of the aerosol particles was imaged under the electron microscope. The size distributions obtained by scanning electron microscopy showed good agreement with the Twin Differential Mobility Sizer in the Aitken mode, whereas in the accumulation mode the size determination was critically dependent on the contrast of the aerosol with the Formvar-coated copper grid. The morphological properties (elongation, circularity) changed with the number of days the air masses spent over the pack-ice area north of 80° before the aerosol particles were collected at the position of the icebreaker and are thus an appropriate measure to characterize transformation processes of ambient aerosol particles.

  • 12. Holl, Gerrit
    et al.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, C.
    Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique, Centre National de la Recherche Scientifique, Observatoire de Paris.
    Collocating satellite-based radar and radiometer measurements: methodology and usage examples2010In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 3, no 3, 693-708 p.Article in journal (Refereed)
    Abstract [en]

    Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) on-board NOAA-18 and the Cloud Profiling Radar (CPR) on-board CloudSat. First, a simple method is presented to obtain those collocations and this method is compared with a more complicated approach found in literature. We present the statistical properties of the collocations, with particular attention to the effects of the differences in footprint size. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. Most of those collocations contain at least ten CloudSat pixels and image relatively homogeneous scenes. In the second part, we present three possible applications for the collocations. Firstly, we use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found to be significantly larger than those from the MSPPS. Secondly, we compare the relation between IWP and MHS channel 5 (190.311 GHz) brightness temperature for two datasets: the collocated dataset, and an artificial dataset. We find a larger variability in the collocated dataset. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. We also study the effect of adding measurements from the High Resolution Infrared Radiation Sounder (HIRS), channels 8 (11.11 mu m) and 11 (8.33 mu m). This shows a small improvement in the retrieval quality. The collocations described in the article are available for public use

  • 13. Karnezi, E.
    et al.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pandis, S. N.
    Measuring the atmospheric organic aerosol volatility distribution: a theoretical analysis2014In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 7, no 9, 2953-2965 p.Article in journal (Refereed)
    Abstract [en]

    Organic compounds represent a significant fraction of submicrometer atmospheric aerosol mass. Even if most of these compounds are semi-volatile in atmospheric concentrations, the ambient organic aerosol volatility is quite uncertain. The most common volatility measurement method relies on the use of a thermodenuder (TD). The aerosol passes through a heated tube where its more volatile components evaporate, leaving the less volatile components behind in the particulate phase. The typical result of a thermodenuder measurement is the mass fraction remaining (MFR), which depends, among other factors, on the organic aerosol (OA) vaporization enthalpy and the accommodation coefficient. We use a new method combining forward modeling, introduction of experimental error, and inverse modeling with error minimization for the interpretation of TD measurements. The OA volatility distribution, its effective vaporization enthalpy, the mass accommodation coefficient and the corresponding uncertainty ranges are calculated. Our results indicate that existing TD-based approaches quite often cannot estimate reliably the OA volatility distribution, leading to large uncertainties, since there are many different combinations of the three properties that can lead to similar thermograms. We propose an improved experimental approach combining TD and isothermal dilution measurements. We evaluate this experimental approach using the same model, and show that it is suitable for studies of OA volatility in the lab and the field.

  • 14.
    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 University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    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 Station2013In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 6, no 9, 2311-2338 p.Article in journal (Refereed)
    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

  • 15.
    Larsson, Richard
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Rayer, Peter
    UK Met Office, Exeter.
    Saunders, Roger
    UK Met Office, Exeter.
    Bell, William
    UK Met Office, Exeter.
    Booton, Anna
    UK Met Office, Exeter.
    Buehler, Stephan A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, Viju E.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 2, 841-857 p.Article in journal (Refereed)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 16.
    Milz, Mathias
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Clarmann, T. von
    Forschungszentrum Karlsruhe.
    Bernath, P.
    University of York, Department of Chemistry.
    Boone, C.
    University of Waterloo, Deptment of Chemistry, Waterloo.
    Buehler, Stefan
    Chauhan, S.
    Forschungszentrum Karlsruhe.
    Deuber, B.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Feist, D.G.
    Max-Planck-Institut für Biogeochemie, Jena.
    Funke, B.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Glatthor, N.
    Forschungszentrum Karlsruhe.
    Grabowski, U.
    Forschungszentrum Karlsruhe.
    Griesfeller, A.
    CNRS, UVSQ, LATMOS, Verrieres Le Buisson.
    Haefele, A.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Höpfner, M.
    Forschungszentrum Karlsruhe.
    Kämpfer, N.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Kellmann, S.
    Forschungszentrum Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe.
    Müller, S.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Nakajima, H.
    National Institute for Environmental Studies, Tsukuba.
    Oelhaf, H.
    Forschungszentrum Karlsruhe.
    Remsberg, E.
    NASA, Langley Research Centre, Scientific Directorate.
    Rohs, S.
    Forschungszentrum Julich.
    Russell, J.M.
    Hampton University, Department of Physics.
    Schiller, C.
    Forschungszentrum Julich.
    Sugita, T.
    National Institute for Environmental Studies, Tsukuba.
    Zhang, G.
    Forschungszentrum Karlsruhe.
    Validation of water vapour profiles (version 13) retrieved by the IMK/IAA scientific retrieval processor based on full resolution spectra measured by MIPAS on board Envisat2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, no 2, 379-399 p.Article in journal (Refereed)
    Abstract [en]

    Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with the full resolution mode between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The estimated precision for MIPAS is 5 to 10% in the stratosphere, depending on altitude, latitude, and season. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System(AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). For the in-situ measurements and the ground based, air- and balloon borne remote sensing instruments, the measurements are restricted to central and northern Europe. The comparisons to satellite-borne instruments are predominantly at mid- to high latitudes on both hemispheres. In the stratosphere there is no clear indicationof a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. Theresults of chi2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the chi2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.

  • 17.
    Navas-Guzmán, Francisco
    et al.
    Institute of Applied Physics, University of Bern.
    Kämpfer, Nklaus
    Institute of Applied Physics, University of Bern.
    Murk, Axel
    Institute of Applied Physics, University of Bern.
    Larsson, Richard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    Eriksson, Patrik
    Chalmers University of Technology, Chalmers University of Technology, Department of Earth and Space Sciences.
    Zeeman effect in atmospheric O2 measured by ground-based microwave radiometry2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 4, 1863-1874 p.Article in journal (Refereed)
    Abstract [en]

    In this work we study the Zeeman effect on stratospheric O2 using ground-based microwave radiometer measurements. The interaction of the Earth magnetic field with the oxygen dipole leads to a splitting of O2 energy states, which polarizes the emission spectra. A special campaign was carried out in order to measure this effect in the oxygen emission line centered at 53.07 GHz. Both a fixed and a rotating mirror were incorporated into the TEMPERA (TEMPERature RAdiometer) in order to be able to measure under different observational angles. This new configuration allowed us to change the angle between the observational path and the Earth magnetic field direction. Moreover, a high-resolution spectrometer (1 kHz) was used in order to measure for the first time the polarization state of the radiation due to the Zeeman effect in the main isotopologue of oxygen from ground-based microwave measurements. The measured spectra showed a clear polarized signature when the observational angles were changed, evidencing the Zeeman effect in the oxygen molecule. In addition, simulations carried out with the Atmospheric Radiative Transfer Simulator (ARTS) allowed us to verify the microwave measurements showing a very good agreement between model and measurements. The results suggest some interesting new aspects for research of the upper atmosphere

  • 18.
    Norin, Lars
    SMHI, Research Department, Atmospheric remote sensing.
    A quantitative analysis of the impact of wind turbines on operational Doppler weather radar data2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 2, 593-609 p.Article in journal (Refereed)
    Abstract [en]

    In many countries wind turbines are rapidly growing in numbers as the demand for energy from renewable sources increases. The continued deployment of wind turbines can, however, be problematic for many radar systems, which are easily disturbed by turbines located in the radar line of sight. Wind turbines situated in the vicinity of Doppler weather radars can lead to erroneous precipitation estimates as well as to inaccurate wind and turbulence measurements. This paper presents a quantitative analysis of the impact of a wind farm, located in southeastern Sweden, on measurements from a nearby Doppler weather radar. The analysis is based on 6 years of operational radar data. In order to evaluate the impact of the wind farm, average values of all three spectral moments (the radar reflectivity factor, absolute radial velocity, and spectrum width) of the nearby Doppler weather radar were calculated, using data before and after the construction of the wind farm. It is shown that all spectral moments, from a large area at and downrange from the wind farm, were impacted by the wind turbines. It was also found that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. It is shown that this in part can be explained by detection by the radar sidelobes and by scattering off increased levels of dust and turbulence. In a detailed analysis, using data from a single radar cell, frequency distributions of all spectral moments were used to study the competition between the weather signal and wind turbine clutter. It is shown that, when weather echoes give rise to higher reflectivity values than those of the wind farm, the negative impact of the wind turbines is greatly reduced for all spectral moments.

  • 19.
    Norin, Lars
    SMHI, Research Department, Atmospheric remote sensing.
    Wind turbine impact on operational weather radar I/Q data: characterisation and filtering2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 5, 1739-1753 p.Article in journal (Refereed)
  • 20.
    Norin, Lars
    et al.
    SMHI, Research Department, Atmospheric remote sensing.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    L'Ecuyer, T. S.
    Wood, N. B.
    Smalley, M.
    Intercomparison of snowfall estimates derived from the CloudSat Cloud Profiling Radar and the ground-based weather radar network over Sweden2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 12, 5009-5021 p.Article in journal (Refereed)
    Abstract [en]

    Accurate snowfall estimates are important for both weather and climate applications. Ground-based weather radars and space-based satellite sensors are often used as viable alternatives to rain gauges to estimate precipitation in this context. In particular, the Cloud Profiling Radar (CPR) on board CloudSat is proving to be a useful tool to map snowfall globally, in part due to its high sensitivity to light precipitation and its ability to provide near-global vertical structure. CloudSat snowfall estimates play a particularly important role in the high-latitude regions as other ground-based observations become sparse and passive satellite sensors suffer from inherent limitations. In this paper, snowfall estimates from two observing systems-Swerad, the Swedish national weather radar network, and CloudSat - are compared. Swerad offers a well-calibrated data set of precipitation rates with high spatial and temporal resolution, at very high latitudes. The measurements are anchored to rain gauges and provide valuable insights into the usefulness of CloudSat CPR's snowfall estimates in the polar regions. In total, 7 : 2 x 10(5) matchups of CloudSat and Swerad observations from 2008 through 2010 were intercompared, covering all but the summer months (June to September). The intercomparison shows encouraging agreement between the two observing systems despite their different sensitivities and user applications. The best agreement is observed when CloudSat passes close to a Swerad station (46-82 km), where the observational conditions for both systems are comparable. Larger disagreements outside this range suggest that both platforms have difficulty with shallow snow but for different reasons. The correlation between Swerad and CloudSat degrades with increasing distance from the nearest Swerad station, as Swerad's sensitivity decreases as a function of distance. Swerad also tends to overshoot low-level precipitating systems further away from the station, leading to an underestimation of snowfall rate and occasionally to missing precipitation altogether. Several statistical metrics-including the probability of detection, false alarm rate, hit rate, and Pierce's skill score - are calculated. The sensitivity of these metrics to the snowfall rate, as well as to the distance from the nearest radar station, are summarised. This highlights the strengths and the limitations of both observing systems at the lower and upper ends of the snowfall distributions as well as the range of uncertainties that can be expected from these systems in high-latitude regions.

  • 21.
    Norin, Lars
    et al.
    SMHI, Research Department, Atmospheric remote sensing.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    L'Ecuyer, Tristan S.
    The sensitivity of snowfall to weather states over Sweden2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 9, 3249-3263 p.Article in journal (Refereed)
  • 22.
    Osterwalder, S.
    et al.
    Univ Basel, Dept Environm Sci, Basel, Switzerland..
    Fritsche, J.
    Univ Basel, Dept Environm Sci, Basel, Switzerland..
    Alewell, C.
    Univ Basel, Dept Environm Sci, Basel, Switzerland..
    Schmutz, M.
    Univ Basel, Dept Environm Sci, Basel, Switzerland..
    Nilsson, M. B.
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Jocher, G.
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Sommar, J.
    Chinese Acad Sci, State Key Lab Environm Geochem, Guiyang, Peoples R China..
    Rinne, J.
    Univ Helsinki, Dept Geosci & Geog, Helsinki, Finland.;Finnish Meteorol Inst, FIN-00101 Helsinki, Finland..
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    A dual-inlet, single detector relaxed eddy accumulation system for long-term measurement of mercury flux2016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 2, 509-524 p.Article in journal (Refereed)
    Abstract [en]

    The fate of anthropogenic emissions of mercury (Hg) to the atmosphere is influenced by the exchange of elemental Hg with the earth surface. This exchange holds the key to a better understanding of Hg cycling from local to global scales, which has been difficult to quantify. To advance research about land-atmosphere Hg interactions, we developed a dual-inlet, single detector relaxed eddy accumulation (REA) system. REA is an established technique for measuring turbulent fluxes of trace gases and aerosol particles in the atmospheric surface layer. Accurate determination of gaseous elemental mercury (GEM) fluxes has proven difficult due to technical challenges presented by extremely small concentration differences (typically < 0.5 ngm(-3)) between updrafts and downdrafts. We present an advanced REA design that uses two inlets and two pairs of gold cartridges for continuous monitoring of GEM fluxes. This setup reduces the major uncertainty created by the sequential sampling in many previous designs. Additionally, the instrument is equipped with a GEM reference gas generator that monitors drift and recovery rates. These innovations facilitate continuous, autonomous measurement of GEM flux. To demonstrate the system performance, we present results from field campaigns in two contrasting environments: an urban setting with a heterogeneous fetch and a boreal peatland during snowmelt. The observed average emission rates were 15 and 3 n gm(-2) h(-1), respectively. We believe that this dual-inlet, single detector approach is a significant improvement of the REA system for ultra-trace gases and can help to advance our understanding of long-term land-atmosphere GEM exchange.

  • 23. Reid, Will
    et al.
    Achtert, Peggy
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ivchenko, Nickolay
    Magnusson, Patrick
    Kuremyr, Tobias
    Shepenkov, Valeriy
    Tibert, Gunnar
    Technical Note: A novel rocket-based in situ collection technique for mesospheric and stratospheric aerosol particles2013In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 6, no 3, 777-785 p.Article in journal (Refereed)
    Abstract [en]

    A technique for collecting aerosol particles between altitudes of 17 and 85 km is described. Spin-stabilized collection probes are ejected from a sounding rocket allowing for multi-point measurements. Each probe is equipped with 110 collection samples that are 3 mm in diameter. The collection samples are one of three types: standard transmission electron microscopy carbon grids, glass fibre filter paper or silicone gel. Collection samples are exposed over a 50 m to 5 km height range with a total of 45 separate ranges. Post-flight electron microscopy will give size-resolved information on particle number, shape and elemental composition. Each collection probe is equipped with a suite of sensors to capture the probe's status during the fall. Parachute recovery systems along with GPS-based localization will ensure that each probe can be located and recovered for post-flight analysis.

  • 24. Renard, Jean-Baptiste
    et al.
    Dulac, Francois
    Berthet, Gwenael
    Lurton, Thibaut
    Vignelles, Damien
    Jegou, Fabrice
    Tonnelier, Thierry
    Jeannot, Matthieu
    Coute, Benoit
    Akiki, Rony
    Verdier, Nicolas
    Mallet, Marc
    Gensdarmes, Francois
    Charpentier, Patrick
    Mesmin, Samuel
    Duverger, Vincent
    Dupont, Jean-Charles
    Elias, Thierry
    Crenn, Vincent
    Sciare, Jean
    Zieger, Paul
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Salter, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Roberts, Tjarda
    Giacomoni, Jerome
    Gobbi, Matthieu
    Hamonou, Eric
    Olafsson, Haraldur
    Dagsson-Waldhauserova, Pavla
    Camy-Peyret, Claude
    Mazel, Christophe
    Decamps, Thierry
    Piringer, Martin
    Surcin, Jeremy
    Daugeron, Daniel
    LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles - Part 12016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 4, 1721-1742 p.Article in journal (Refereed)
    Abstract [en]

    The study of aerosols in the troposphere and in the stratosphere is of major importance both for climate and air quality studies. Among the numerous instruments available, optical aerosol particles counters (OPCs) provide the size distribution in diameter range from about 100 nm to a few tens of mu m. Most of them are very sensitive to the nature of aerosols, and this can result in significant biases in the retrieved size distribution. We describe here a new versatile optical particle/sizer counter named LOAC (Light Optical Aerosol Counter), which is light and compact enough to perform measurements not only at the surface but under all kinds of balloons in the troposphere and in the stratosphere. LOAC is an original OPC performing observations at two scattering angles. The first one is around 12 degrees, and is almost insensitive to the refractive index of the particles; the second one is around 60 degrees and is strongly sensitive to the refractive index of the particles. By combining measurement at the two angles, it is possible to retrieve the size distribution between 0.2 and 100 mu m and to estimate the nature of the dominant particles (droplets, carbonaceous, salts and mineral particles) when the aerosol is relatively homogeneous. This typology is based on calibration charts obtained in the laboratory. The uncertainty for total concentrations measurements is +/- 20% when concentrations are higher than 1 particle cm 3 (for a 10 min integration time). For lower concentrations, the uncertainty is up to about +/- 60% for concentrations smaller than 10 2 particle cm(-3). Also, the uncertainties in size calibration are +/- 0.025 mu m for particles smaller than 0.6 mu m, 5% for particles in the 0.7-2 mu m range, and 10% for particles greater than 2 mu m. The measurement accuracy of sub-micronic particles could be reduced in a strongly turbid case when concentration of particles > 3 mu m exceeds a few particles cm(-3). Several campaigns of cross-comparison of LOAC with other particle counting instruments and remote sensing photometers have been conducted to validate both the size distribution derived by LOAC and the retrieved particle number density. The typology of the aerosols has been validated in well-defined conditions including urban pollution, desert dust episodes, sea spray, fog, and cloud. Comparison with reference aerosol mass monitoring instruments also shows that the LOAC measurements can be successfully converted to mass concentrations.

  • 25. Renard, Jean-Baptiste
    et al.
    Dulac, Francois
    Berthet, Gwenael
    Lurton, Thibaut
    Vignelles, Damien
    Jegou, Fabrice
    Tonnelier, Thierry
    Jeannot, Matthieu
    Coute, Benoit
    Akiki, Rony
    Verdier, Nicolas
    Mallet, Marc
    Gensdarmes, Francois
    Charpentier, Patrick
    Mesmin, Samuel
    Duverger, Vincent
    Dupont, Jean-Charles
    Elias, Thierry
    Crenn, Vincent
    Sciare, Jean
    Zieger, Paul
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Salter, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Roberts, Tjarda
    Giacomoni, Jerome
    Gobbi, Matthieu
    Hamonou, Eric
    Olafsson, Haraldur
    Dagsson-Waldhauserova, Pavla
    Camy-Peyret, Claude
    Mazel, Christophe
    Decamps, Thierry
    Piringer, Martin
    Surcin, Jeremy
    Daugeron, Daniel
    LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles - Part 22016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 8, 3673-3686 p.Article in journal (Refereed)
    Abstract [en]

    In the companion (Part I) paper, we have described and evaluated a new versatile optical particle counter/sizer named LOAC (Light Optical Aerosol Counter), based on scattering measurements at angles of 12 and 60A degrees. That allows for some typology identification of particles (droplets, carbonaceous, salts, and mineral dust) in addition to size-segregated counting in a large diameter range from 0.2aEuro-A mu m up to possibly more than 100aEuro-A mu m depending on sampling conditions (Renard et al., 2016). Its capabilities overpass those of preceding optical particle counters (OPCs) allowing the characterization of all kind of aerosols from submicronic-sized absorbing carbonaceous particles in polluted air to very coarse particles (> 10-20aEuro-A mu m in diameter) in desert dust plumes or fog and clouds. LOAC's light and compact design allows measurements under all kinds of balloons, on-board unmanned aerial vehicles (UAVs) and at ground level. We illustrate here the first LOAC airborne results obtained from a UAV and a variety of scientific balloons. The UAV was deployed in a peri-urban environment near Bordeaux in France. Balloon operations include (i) tethered balloons deployed in urban environments in Vienna (Austria) and Paris (France), (ii) pressurized balloons drifting in the lower troposphere over the western Mediterranean (during the Chemistry-Aerosol Mediterranean Experiment - ChArMEx campaigns), (iii) meteorological sounding balloons launched in the western Mediterranean region (ChArMEx) and from Aire-sur-l'Adour in south-western France (VOLTAIRE-LOAC campaign). More focus is put on measurements performed in the Mediterranean during (ChArMEx) and especially during African dust transport events to illustrate the original capability of balloon-borne LOAC to monitor in situ coarse mineral dust particles. In particular, LOAC has detected unexpected large particles in desert sand plumes.

  • 26.
    Rydberg, Bengt
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Murtagh, Donal
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Non-Gaussian Bayesian retrieval of tropical upper tropospheric cloud ice and water vapour from Odin-SMR measurements2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 2, no 2, 621-637 p.Article in journal (Refereed)
    Abstract [en]

    Improved Odin-SMR retrievals of upper tropospheric water are presented. The new retrieval algorithm retrieves humidity and cloud ice mass simultaneously and takes into account of cloud inhomogeneities. Both these aspects are introduced for microwave limb sounding inversions for the first time. A Bayesian methodology is applied allowing for a formally correct treatment of non-unique retrieval problems involving non-Gaussian statistics. Cloud structure information from CloudSat is incorporated into the retrieval algorithm. This removes a major limitation of earlier inversion methods where uniform cloud layers were assumed and caused a systematic retrieval error. The core part ofthe retrieval technique is the generation of a database that must closely represent real conditions. Good agreement with Odin-SMR observations indicates that this requirement is met. The retrieval precision is determined to be about 5–17% RHi and 65% for humidity and cloud ice mass, respectively.For both quantities, the vertical resolution is about 5 km and the best retrieval performance is found between 11 and 15 km. New data show a significantly improved agreement with CloudSat cloud ice mass retrievals, at the same time consistency with the Aura MLS humidity results is maintained. The basics of the approach presented can be applied for all passive cloud observations and should be of broad interest. The results can also be taken as a demonstration of the potential of down-looking sub-mm radiometry for global measurements of cloud ice properties.

  • 27.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, S. A.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Division of Space Technology, SRT, Luleä University of Technology.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, 4491-4505 p.Article in journal (Refereed)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectroradiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. A technical upgrade including a new high-frequency amplifier and sideband filter has improved the signal to noise ratio by a factor of 2.4. Since this upgrade the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper. Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid- and tropical latitudes (67°22′ N/26°38′ E, 46°57′ N/7°26′ E, 43°56′ N/5°43′ E and 21°04′ S/55°23′ E) for time periods between 5.5 and 11 months. The data presented in this paper are daily average wind profiles with typical uncertainties and resolutions of 10 to 20 m s−1 and 10 to 16 km, respectively. A comparison between the data series from WIRA and European Centre for Medium-Range Weather Forecasts (ECMWF) model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 50% have been found.

  • 28.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, 7717-7752 p.Article in journal (Refereed)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectro radiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. Since a technical upgrade which improved the signal to noise ratio by a factor of 2.4 the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper.Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid and tropical latitudes for time periods between 5.5 and 11 months. A comparison between the data series from WIRA and ECMWF model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 40% have been found.

  • 29.
    Sato, T.O.
    et al.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    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.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Ochiai, S.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kikuchi, K.
    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 University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Urban, J.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Murtagh, D.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Yasui, M.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kasai, Y.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    Strato-mesospheric ClO observations by SMILES: error analysis and diurnal variation2012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 11, 2809-2825 p.Article in journal (Refereed)
    Abstract [en]

    Chlorine monoxide (ClO) is the key species for anthropogenic ozone losses in the middle atmosphere. We observed ClO diurnal variations using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station, which has a non-sun-synchronous orbit. This includes the first global observations of the ClO diurnal variation from the stratosphere up to the mesosphere. The observation of mesospheric ClO was possible due to 10–20 times better signal-to-noise (S/N) ratio of the spectra than those of past or ongoing microwave/submillimeter-wave limb-emission sounders. We performed a quantitative error analysis for the strato- and mesospheric ClO from the Level-2 research (L2r) product version 2.1.5 taking into account all possible contributions of errors, i.e. errors due to spectrum noise, smoothing, and uncertainties in radiative transfer model and instrument functions. The SMILES L2r v2.1.5 ClO data are useful over the range from 0.01 and 100 hPa with a total error estimate of 10–30 pptv (about 10%) with averaging 100 profiles. The SMILES ClO vertical resolution is 3–5 km and 5–8 km for the stratosphere and mesosphere, respectively. The SMILES observations reproduced the diurnal variation of stratospheric ClO, with peak values at midday, observed previously by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite (UARS/MLS). Mesospheric ClO demonstrated an opposite diurnal behavior, with nighttime values being larger than daytime values. A ClO enhancement of about 100 pptv was observed at 0.02 to 0.01 hPa (about 70–80 km) for 50° N–65° N from January–February 2010. The performance of SMILES ClO observations opens up new opportunities to investigate ClO up to the mesopause.

  • 30. Shupe, M. D.
    et al.
    Brooks, I. M.
    Canut, G.
    Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar2012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 6, 1375-1385 p.Article in journal (Refereed)
    Abstract [en]

    Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4–6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tethered-balloon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2–3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds.

  • 31. Sporre, Moa K.
    et al.
    O'Connor, Ewan J.
    Håkansson, Nina
    SMHI, Research Department, Atmospheric remote sensing.
    Thoss, Anke
    SMHI, Research Department, Atmospheric remote sensing.
    Swietlicki, Erik
    Petaja, Tuukka
    Comparison of MODIS and VIIRS cloud properties with ARM ground-based observations over Finland2016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 7, 3193-3203 p.Article in journal (Refereed)
1 - 31 of 31
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