Digitala Vetenskapliga Arkivet

Endre søk
Begrens søket
12 1 - 50 of 94
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ashraf, Shakeel
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Niskanen, Ilpo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. University of Oulu, Finland.
    Kanyathare, Boniphace
    Electronics and Telecommunications Department, Dar es salaam Institute of Technology, Tanzania.
    Vartiainen, Erik
    LUT School of Engineering Science, Lappeenranta University of Technology, Finland.
    Mattsson, Claes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Heikkilä, Rauno
    Faculty of Technology, Structures and Construction Technology, University of Oulu, Finland.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Determination of complex refractive index of SU-8 by Kramers-Kronig dispersion relation method at the wavelength range 2.5 – 22.0 μm2019Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 224, s. 309-311Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate determination of the complex refractive index of SU-8 epoxy has significant for the wide variety of applications in optical sensor technology at IR range. The complex refractive index of SU-8 is determined by recording the transmission of light spectra for the wavelength range of 2.5 – 22.0 μm.  The data analysis is based on the Kramers-Kronig dispersion relation method. The method has several merits, such as ease of operation, non-contact technique, measurement accuracy, and rapid measurement. The present method is not restricted to the case of SU-8 but it is also proposed to be applicable across a broad range of applications, such as assessment of the optical properties of paints and biomedical samples.

  • 2.
    Atalay, B.
    et al.
    Division of Mathematical Physics, Department of Physics, Lund University, LundSE-22100, Sweden; Department of Physics, Çanakkale Onsekiz Mart University, Çanakkale17100, Turkey.
    Jönsson, P.
    Malmö universitet, Fakulteten för teknik och samhälle (TS), Institutionen för materialvetenskap och tillämpad matematik (MTM).
    Brage, T.
    Division of Mathematical Physics, Department of Physics, Lund University, LundSE-22100, Sweden.
    Extended relativistic multiconfiguration calculations of energy levels and transition properties in singly ionized tin2023Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 294, s. 108392-108392, artikkel-id 108392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations are performed for 22 states in singly ionized tin (Sn II) belonging to the 5s2ns (n=6,7), 5s2nd (n=5,6), 5s5p2 even parity configurations and the 5s2np (n=5,6,7), 5s24f odd parity configurations. Valence-valence and core-valence correlation effects are taken into account through configuration state function (CSF) expansions. Complete and consistent data sets of level energies, wavelengths, oscillator strengths, lifetimes and transition rates among all these states are given. The results are compared with existing theoretical and experimental results. There is an excellent agreement for calculated excitation energies with experimental data from the NIST database. Lifetimes and transition rates are also in agreement with the results from previous calculations and available measurements for most of the transitions.

  • 3.
    Buehler, Stefan A.
    et al.
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    Eriksson, P.
    Department of Radio and Space Science, Chalmers University of Technology, Gothenburg, Sweden.
    Kuhn, Thomas
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    von Engeln, Axel
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    Verdes, C.
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    ARTS, the atmospheric radiative transfer simulator2005Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 91, nr 1, s. 65-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    RTS is a modular program that simulates atmospheric radiative transfer. The paper describes ARTS version 1.0, which is applicable in the absence of scattering. An overview over all major parts of the model is given: calculation of absorption coefficients, the radiative transfer itself, and the calculation of Jacobians. ARTS can be freely used under a GNU general public license. Unique features of the program are its scalability and modularity, the ability to work with different sources of spectroscopic parameters, the availability of several self-consistent water continuum and line absorption models, and the analytical calculation of Jacobians.

    Fulltekst (pdf)
    fulltext
  • 4.
    Buehler, Stefan A.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, FitzRoy Road, Exeter EX1 3PB, UK.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, P.
    Radio and Space Science, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Efficient radiative transfer simulations for a broadband infrared radiometer—Combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing2010Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, nr 4, s. 602-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method to efficiently simulate the measurements of a broadband infrared instrument. The High Resolution Infrared Radiation Sounder (HIRS) instrument is used as example to illustrate the method. The method uses two basic ideas. Firstly, the channel radiance can be approximated by a weighted mean of the radiance at some representative frequencies, where the weights can be determined by linear regression. Secondly, a near-optimal set of representative frequencies can be found by simulated annealing.

    The paper does not only describe and analyze the method, it also describes how the method was used to derive optimized frequency grids for the HIRS instruments on the satellites TIROS N, NOAA 6-19, and Metop A. The grids and weights, as well as the optimization algorithm itself are openly available under a GNU public license.

  • 5.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Absorption lookup tables in the radiative transfer model ARTS2011Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, nr 10, s. 1559-1567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.

  • 6.
    Buehler, Stefan
    et al.
    Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
    von Engeln, A.
    Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
    Brocard, E.
    Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
    John, Viju Oommen
    Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
    Kuhn, Thomas
    I. Physikalisches Institut, Universitaet zu Koeln, Cologne, Germany.
    Eriksson, Patrick
    Department of Radio and Space Science, Chalmers University of Technology, Gothenburg, Sweden.
    Recent developments in the line-by-line modeling of outgoing longwave radiation2006Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 98, nr 3, s. 446-457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High frequency resolution radiative transfer model calculations with the Atmospheric Radiative Transfer Simulator (ARTS) were used to simulate the clear-sky outgoing longwave radiative flux (OLR) at the top of the atmosphere. Compared to earlier calculations by Clough and coworkers the model used a spherical atmosphere instead of a plane parallel atmosphere, updated spectroscopic parameters from HITRAN, and updated continuum parameterizations from Mlawer and coworkers. These modifications lead to a reduction in simulated OLR by approximately 4.1%, the largest part, approximately 2.5%, being due to the absence of the plane parallel approximation. As a simple application of the new model, the sensitivity of OLR to changes in humidity, carbon dioxide concentration, and temperature were investigated for different cloud-free atmospheric scenarios. It was found that for the tropical scenario a 20% change in humidity has a larger impact than a doubling of the carbon dioxide concentration. The sensitive altitude region for temperature and humidity changes is the entire free troposphere, including the upper troposphere where humidity data quality is poor.

    Fulltekst (pdf)
    fulltext
  • 7. Chen, Zhan-Bin
    et al.
    Guo, Xue-Ling
    Wang, Kai
    Malmö universitet, Fakulteten för teknik och samhälle (TS), Institutionen för materialvetenskap och tillämpad matematik (MTM).
    Theoretical energies, transition rates, lifetimes, hyperfine interaction constants and Lande g(J-)factors for the Se XXVII spectrum of fusion interest2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 206, s. 213-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An extensive set of level energies, wavelengths, line strengths, oscillator strengths, lifetimes, hyperfine structures, Lande g(J)-factors, electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transition rates among the lowest 318 states arising from the 2s(2)2p(4), 2s2(p)5, 2p(6), 2s(2)2p(3)3l (l = 0, 1, 2), 2s2p(4)31 (l = 0, 1, 2), 2p(5)3l (l = 0, 1, 2), and 2s(2)2p(3)4l (l = 0, 1, 2, 3) configurations has been obtained for Se XXVII. These new data, calculated within the frameworks of the multi-configuration Dirac-Hartree-Fock method and the second-order many-body perturbation theory, fill in the gap existing in the atomic data needed for the diagnostic processes of tokamak plasmas. Using two methods allowed us to make an intercomparison and to estimate the uncertainties on the obtained data. The results arising in the two sets of calculations are quite close, suggesting that there is a high degree of convergence achieved in our work. i.e., our two sets of energies agree to better than 0.02%, and the lifetimes mostly agree to within 2%. Comparison is also made with the limited number of experimental data and previous computations to assess the accuracy of our calculations. (C) 2017 Elsevier Ltd. All rights reserved.

  • 8. Dubernet, M. L.
    et al.
    Boudon, V.
    Culhane, J. L.
    Dimitrijevic, M. S.
    Fazliev, A. Z.
    Joblin, C.
    Kupka, F.
    Leto, G.
    Le Sidaner, P.
    Loboda, P. A.
    Mason, H. E.
    Mason, N. J.
    Mendoza, C.
    Mulas, G.
    Millar, T. J.
    Nunez, L. A.
    Perevalov, V. I.
    Piskunov, N.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Ralchenko, Y.
    Rixon, G.
    Rothman, L. S.
    Roueff, E.
    Ryabchikova, T. A.
    Ryabtsev, A.
    Sahal-Brechot, S.
    Schmitt, B.
    Schlemmer, S.
    Tennyson, J.
    Tyuterev, V. G.
    Walton, N. A.
    Wakelam, V.
    Zeippen, C. J.
    Virtual atomic and molecular data centre2010Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, nr 15, s. 2151-2159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu) is a European Union funded collaboration between groups involved in the generation, evaluation, and use of atomic and molecular data. VAMDC aims to build a secure, documented, flexible and interoperable e-science environment-based interface to existing atomic and molecular data. The project will cover establishing the core consortium, the development and deployment of the infrastructure and the development of interfaces to the existing atomic and molecular databases. It will also provide a forum for training potential users and dissemination of expertise worldwide. This review describes the scope of the VAMDC project; it provides a survey of the atomic and molecular data sets that will be included plus a discussion of how they will be integrated. Some applications of these data are also discussed.

  • 9.
    El-Kader, M.S.A.
    et al.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University.
    Godet, J-L
    Laboratoire de photonique d'Angers, Université d'Angers.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Maroulis, G.
    Department of Chemistry, University of Patras.
    Multi-property isotropic intermolecular potentials and predicted spectral lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) for H2Ne, −Kr and −Xe2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 209, s. 232-242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum mechanical lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) at room temperature (295 K) are computed for gaseous mixtures of molecular hydrogen with neon, krypton and xenon. The induced spectra are detected using theoretical values for induced dipole moment, pair-polarizability trace and anisotropy, hyper-polarizability and updated intermolecular potentials. Good agreement is observed for all spectra when the literature and the present potentials which are constructed from the transport and thermo-physical properties are used.

  • 10.
    Eriksson, P.
    et al.
    Chalmers University of Technology.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Davis, C.P.
    Meteorological Service of New Zealand.
    Emde, C.
    Meteorological Institute, Ludwig-Maximilians-Universität, Munchen.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    ARTS, the atmospheric radiative transfer simulator, version 22011Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, nr 10, s. 1551-1558Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The second version of the atmospheric radiative transfer simulator, ARTS, is introduced. This is a general software package for long wavelength radiative transfer simulations, with a focus on passive microwave observations. The core part provides a workspace environment, in line with script languages. New for this version is an agenda mechanism that gives a high degree of modularity. The framework is intended to be as general as possible: the polarisation state can be fully described, the model atmosphere can be one- (1D), two- (2D) or three-dimensional (3D), a full description of geoid and surface is possible, observation geometries from the ground, from satellite, and from aeroplane or balloon are handled, and surface reflection can be treated in simple or complex manners. Remote sensing applications are supported by a comprehensive and efficient treatment of sensor characteristics. Jacobians can be calculated for the most important atmospheric variables in non-scattering conditions. Finally, the most prominent feature is the rigorous treatment of scattering that has been implemented in two modules: a discrete ordinate iterative approach mainly used for 1D atmospheres, and a Monte Carlo approach which is the preferred algorithm for 3D atmospheres. ARTS is freely available, and maintained as an open-source project.

  • 11.
    Eriksson, Patrick
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jimenez, Carlos
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Qpack: a general tool for instrument simulation and retrieval work2005Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 91, nr 1, s. 47-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Remote sensing requires a complete observation system, consisting of the instrument, a forward model and a retrieval environment. This paper presents a software tool to complement atmospheric sensors, with focus on passive instruments operating in the mm and sub-mm wavelength regions. The tool is of general character and offers a complete, flexible and fast calculation environment, demonstrated in both preparatory instrument studies and operational inversions. Its features include a rapid approach for modelling of sensor characteristics, several types of data reduction, simple definition of covariance matrices, a large number of retrieval and error quantities, inversion characterisation and random realisation of measurements. The software is freely available for scientific use.

    Fulltekst (pdf)
    FULLTEXT01
  • 12.
    Eriksson, Patrick
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, Carlos
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Murtagh, Donal
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    A Hotelling transformation approach for rapid inversion of atmospheric spectra2002Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 73, nr 6, s. 529-543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atmospheric observations from space often result in spectral data of large dimensions. To allow an optimal inversion of the observed spectra it can be necessary to map the data into a space of smaller dimension. Here several data reduction techniques based on eigenvector expansions of the spectral space are compared. The comparison is done by inverting simulated observations from a microwave limb sounder, the Odin-SMR. For the examples tested, reductions exceeding two orders of magnitude with no negative influence on the retrieval performance are demonstrated. The techniques compared include a novel method developed especially for atmospheric inversions, based on the weighting functions of the variables to be retrieved. The new method shows an excellent performance in practical tests and is both computationally more effective and more flexible than the standard Hotelling transformation.

    Fulltekst (pdf)
    FULLTEXT01
  • 13. Ershov, A. E.
    et al.
    Gerasimov, V. S.
    Gavrilyuk, A. P.
    Karpov, S. V.
    Zakomirnyi, Vadim I.
    KTH. Siberian Federal University, Russian Federation.
    Rasskazov, I. L.
    Polyutov, S. P.
    Thermal limiting effects in optical plasmonic waveguides2017Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 191, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied thermal effects occurring during excitation of optical plasmonic waveguide (OPW) in the form of linear chain of spherical Ag nanoparticles by pulsed laser radiation. It was shown that heating and subsequent melting of the first irradiated particle in a chain can significantly deteriorate the transmission efficiency of OPW that is the crucial and limiting factor and continuous operation of OPW requires cooling devices. This effect is caused by suppression of particle's surface plasmon resonance due to reaching the melting point temperature. We have determined optimal excitation parameters which do not significantly affect the transmission efficiency of OPW.

  • 14.
    Fakhardji, Wissam
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Szabó, Péter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Physics and Materials Science, University of Luxembourg, L-1511, Luxembourg.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Direct method for MD simulations of collision-induced absorption: application to an Ar–Xe gas mixture2021Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 276, artikkel-id 107926Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the reformulation of the classical equations of collision-induced absorption, we present a method to perform the direct computation of the spectral density function. This way the absorption coefficient can be computed from classical molecular dynamics (MD) without the computationally demanding evaluation of the dipole autocorrelation function. In addition, we have developed an algorithm to extract the bound-to-bound dimer contribution to the MD simulated absorption. The method has been tested on the Ar–Xe rare gas system. Comparisons with quantum mechanical (QM) and conventional MD methods validate the approach. The obtained MD bound-to-bound spectra generally agree in shape and magnitude with QM results, including features stemming from rotations and vibrations of the Ar–Xe dimer.

  • 15.
    Foltynowicz, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gustafsson, Jörgen
    School of Engineering, Jönköping University, Jönköping, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wavelength modulation absorption spectrometry from optically pumped collision broadened atoms and molecules2007Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 108, nr 2, s. 220-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theoretical investigation of the influence of optical pumping on wavelength modulation absorption spectrometry (WMAS) signals from collision broadened atoms and molecules is presented. General expressions for the nf-WMAS signal from atomic and molecular systems, modeled as three-level systems that can accommodate both optical saturation and optical pumping, are derived by the use of a previously developed Fourier series-based formalism in combination with rate equations solved under steady-state conditions. The expressions are similar to those describing the nf-WMAS signal from two-level systems that can accommodate optical saturation [Schmidt FM, Foltynowicz A, Gustafsson J, Axner O, WMAS from optically saturated collision-broadened transitions. JQSRT 2005;94:225–54], the difference being the value of the saturation flux, wherefore the general parametric dependence of WMAS signals from optically pumped systems is the same as that from optically saturated systems. The additional effect of optical pumping on the WMAS signal is investigated for three typical cases: molecules or atoms in an ordinary atmosphere, atoms in an inert atmosphere, and atoms or molecules possessing metastable states. The possibility to describe any of these systems with a two-level model is investigated.

  • 16. Foltynowicz, Alexandra
    et al.
    Schmidt, Florian M
    Gustafsson, Jörgen
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Fysik.
    Axner, Ove
    Wavelength modulation absorption spectrometry from optically pumped collision broadened atoms and molecules2007Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 108, nr 2, s. 220-238Artikkel i tidsskrift (Fagfellevurdert)
  • 17.
    Gasteiger, J.
    et al.
    Meteorologisches Institut, Ludwig-Maximilians-Universität, Theresienstr. 37, München, Germany.
    Emde, C.
    Meteorologisches Institut, Ludwig-Maximilians-Universität, Theresienstr. 37, München, Germany.
    Mayer, B.
    Meteorologisches Institut, Ludwig-Maximilians-Universität, Theresienstr. 37, München, Germany.
    Buras, R.
    Meteorologisches Institut, Ludwig-Maximilians-Universität, Theresienstr. 37, München, Germany.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Representative wavelengths absorption parameterization applied to satellite channels and spectral bands2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 148, s. 99-115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate modeling of wavelength-integrated radiative quantities, e.g. integrated over a spectral band or an instrument channel response function, requires computations for a large number of wavelengths if the radiation is affected by gas absorption which typically comprises a complex line structure. In order to increase computational speed of modeling radiation in the Earth׳s atmosphere, we parameterized wavelength-integrals as weighted means over representative wavelengths. We parameterized spectral bands of different widths (1 cm−1, 5 cm−1, and 15 cm−1) in the solar and thermal spectral range, as well as a number of instrument channels on the ADEOS, ALOS, EarthCARE, Envisat, ERS, Landsat, MSG, PARASOL, Proba, Sentinel, Seosat, and SPOT satellites. A root mean square relative deviation lower than 1% from a “training data set” was selected as the accuracy threshold for the parameterization of each band and channel. The training data set included high spectral resolution calculations of radiances at the top of atmosphere for a set of highly variable atmospheric states including clouds and aerosols. The gas absorption was calculated from the HITRAN 2004 spectroscopic data set and state-of-the-art continuum models using the ARTS radiative transfer model. Three representative wavelengths were required on average to fulfill the accuracy threshold. We implemented the parameterized spectral bands and satellite channels in the uvspec radiative transfer model which is part of the libRadtran software package. The parameterization data files, including the representative wavelengths and weights as well as lookup tables of absorption cross sections of various gases, are provided at the libRadtran webpage.In the paper we describe the parameterization approach and its application. We validate the approach by comparing modeling results of parameterized bands and channels with results from high spectral resolution calculations for atmospheric states that were not part of the training data set. Irradiances are not only compared at the top of atmosphere but also at the surface for which this parameterization approach was not optimized. It is found that the parameterized bands and channels provide a good compromise between computation time requirements and uncertainty for typical radiative transfer problems. In particular for satellite radiometer simulations the computation time requirement and the parameterization uncertainty is low. Band-integrated irradiances at any level as well as heating and cooling rates below 20 km can also be modeled with low uncertainty.

  • 18.
    Germann, Matthias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hjältén, Adrian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boudon, Vincent
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS/Université Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47870, Dijon Cedex, France.
    Richard, Cyril
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS/Université Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47870, Dijon Cedex, France.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    A methane line list with sub-MHz accuracy in the 1250 to 1380 cm−1 range from optical frequency comb Fourier transform spectroscopy2022Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 288, artikkel-id 108252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use a Fourier transform spectrometer based on a difference frequency generation optical frequency comb to measure high-resolution, low-pressure, room-temperature spectra of methane in the 1250 – 1380-cm−1 range. From these spectra, we retrieve line positions and intensities of 678 lines of two isotopologues: 157 lines from the 12CH4 ν4 fundamental band, 131 lines from the 13CH4 ν4 fundamental band, as well as 390 lines from two 12CH4 hot bands, ν2 + ν4 ν2 and 2ν4ν4. For another 165 lines from the 12CH4 ν4 fundamental band we retrieve line positions only. The uncertainties of the line positions range from 0.19 to 2.3 MHz, and their median value is reduced by a factor of 18 and 59 compared to the previously available data for the 12CH4 fundamental and hot bands, respectively, obtained from conventional FTIR absorption measurements. The new line positions are included in the global models of the spectrum of both methane isotopologues, and the fit residuals are reduced by a factor of 8 compared to previous absorption data, and 20 compared to emission data. The experimental line intensities have relative uncertainties in the range of 1.5 – 7.7%, similar to those in the previously available data; 235 new 12CH4 line intensities are included in the global model.

    Fulltekst (pdf)
    fulltext
  • 19.
    Germann, Matthias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hjältén, Adrian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tennyson, Jonathan
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Yurchenko, Sergei N.
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Gordon, Iouli E.
    Center for Astrophysics, Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Pett, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range: experimental line list and improved MARVEL analysis2024Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 312, artikkel-id 108782Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use optical frequency comb Fourier transform spectroscopy to record high-resolution, low-pressure, room-temperature spectra of formaldehyde (H212C16O) in the range of 1250 to 1390 cm−1. Through line-by-line fitting, we retrieve line positions and intensities of 747 rovibrational transitions: 558 from the ν6 band, 129 from the ν4 band, and 14 from the ν3 band, as well as 46 from four different hot bands. We incorporate the accurate and precise line positions (0.4 MHz median uncertainty) into the MARVEL (measured active vibration-rotation energy levels) analysis of the H2CO spectrum. This increases the number of MARVEL-predicted energy levels by 82 and of rovibrational transitions by 5382, and substantially reduces uncertainties of MARVEL-derived H2CO energy levels over a large range: from pure rotational levels below 200 cm−1 up to multiply excited vibrational levels at 6000 cm−1. This work is an important step toward filling the gaps in formaldehyde data in the HITRAN database.

    Fulltekst (pdf)
    fulltext
  • 20.
    Gordon, I.E.
    et al.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Rothman, L.S.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hargreaves, R.J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hashemi, R.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karlovets, E.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Skinner, F.M.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Conway, E.K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hill, C.
    Nuclear Data Section, International Atomic Energy Agency, Vienna International Centre, PO Box 100, Vienna, Austria.
    Kochanov, R.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation.
    Tan, Y.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, China.
    Wcisło, P.
    Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziadzka 5, Torun, Poland.
    Finenko, A.A.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation.
    Nelson, K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Bernath, P.F.
    Department of Chemistry, Old Dominion University, VA, Norfolk, United States.
    Birk, M.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Boudon, V.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Campargue, A.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Chance, K.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Coustenis, A.
    Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Paris Observatory, CNRS, PSL University, Sorbonne University, Paris, France.
    Drouin, B.J.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Flaud, J.M.
    Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay, France.
    Gamache, R.R.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States.
    Hodges, J.T.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Jacquemart, D.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Mlawer, E.J.
    Atmospheric and Environmental Research, MA, Lexington, United States.
    Nikitin, A.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perevalov, V.I.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Rotger, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Tennyson, J.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Toon, G.C.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tran, H.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Tyuterev, V.G.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation; Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Adkins, E.M.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Baker, A.
    Division of Astronomy, California Institute of Technology, CA, Pasadena, United States.
    Barbe, A.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Canè, E.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Császár, A.G.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary; Eötvös Loránd University, Institute of Chemistry, Budapest, Hungary.
    Dudaryonok, A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Egorov, O.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Fleisher, A.J.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Fleurbaey, H.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Furtenbacher, T.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Harrison, J.J.
    Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom; University of Leicester, National Centre for Earth Observation, Leicester, United Kingdom; University of Leicester, Leicester Institute for Space and Earth Observation, Leicester, United Kingdom.
    Hartmann, J.M.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University, Palaiseau, France.
    Horneman, V.M.
    Department of Physics, University of Oulu, Finland.
    Huang, X.
    SETI Institute, CA, Mountain View, United States.
    Karman, T.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karns, J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Golisano College of Computing and Information Sciences, Rochester Institute of Technology, NY, Rochester, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Kassi, S.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Kleiner, I.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Kofman, V.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Kwabia-Tchana, F.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Lavrentieva, N.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lee, T.J.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Long, D.A.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Lukashevskaya, A.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lyulin, O.M.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Makhnev, V.Yu.
    Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Matt, W.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Massie, S.T.
    University of Colorado, Laboratory for Atmospheric and Space Physics, CO, Boulder, United States.
    Melosso, M.
    Dipartimento di Chimica “Giacomo Ciamician”, Università di Bologna, Via F. Selmi 2, Bologna, Italy.
    Mikhailenko, S.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Mondelain, D.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Müller, H.S.P.
    I. Physikalisches Institut, Universität zu Köln, Köln, Germany.
    Naumenko, O.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perrin, A.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Polyansky, O.L.
    Department of Physics and Astronomy, University College London, London, United Kingdom; Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Raddaoui, E.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Raston, P.L.
    Department of Chemistry and Biochemistry, James Madison University, VA, Harrisonburg, United States; Department of Chemistry, University of Adelaide, South Australia, Australia.
    Reed, Z.D.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Rey, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Richard, C.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Tóbiás, R.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Sadiek, I.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany.
    Schwenke, D.W.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Starikova, E.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Sung, K.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tamassia, F.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Tashkun, S.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vander Auwera, J.
    Université Libre de Bruxelles, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), C.P. 160/09, Brussels, Belgium.
    Vasilenko, I.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vigasin, A.A.
    Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Pyzhevsky per. 3, Moscow, Russian Federation.
    Villanueva, G.L.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Vispoel, B.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States; Research Unit Lasers and Spectroscopies (LLS), Institute of Life, Earth and Environment (ILEE), University of Namur (UNamur), Namur, Belgium; Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium.
    Wagner, G.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Yachmenev, A.
    Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, Hamburg, Germany; Hamburg Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, Hamburg, Germany.
    Yurchenko, S.N.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    The HITRAN2020 molecular spectroscopic database2022Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 277, artikkel-id 107949Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

    Fulltekst (pdf)
    fulltext
  • 21.
    Gustafsson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt.
    Collision-induced absorption in Ar-Xe: a comparative study of empirical and ab initio interaction potentials and electric dipole moments2022Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 292, artikkel-id 108362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Empirical Barker-Fisher-Watts and modified Tang-Toennies potential energy curves are obtained through fit to experimental vibrational transition energies for argon–argon, xenon–xenon, and argon–xenon pairs. The potentials are tested against experimental thermophysical and transport properties, and agreement is observed. Also, an interaction-induced electric dipole moment curve for the argon–xenon pair is determined through a fit to experimental spectral moments for collision-induced absorption. The argon–xenon potentials and dipole are tested in a complete quantum dynamical calculation of the collision-induced absorption profiles, which can be compared with a laboratory measurement. This provides further analysis of the accuracy of the empirical argon–xenon data, as calculations of absorption profiles are highly sensitive to the input of molecular data.

  • 22.
    Hartmann, Jean-Michel
    et al.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University.
    Tran, Ha
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Armante, Raymond
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University.
    Boulet, Christian
    Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay.
    Campargue, Alain
    Univ. Grenoble Alpes, CNRS.
    Forget, François
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Gianfrani, Livio
    Dipartimento di Matematica e Fisica, Università degli Studi della Campania "Luigi Vanvitelli".
    Gordon, Iouli
    Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division, Cambridge, MA .
    Guerlet, Sandrine
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hodges, Joseph T.
    National Institute of Standards and Technology.
    Kassi, Samir
    Univ. Grenoble Alpes, CNRS.
    Lisak, Daniel
    Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University.
    Thibault, Franck
    Institut de Physique de Rennes, UMR CNRS 6251, Université de Rennes .
    Toon, Geoffrey C.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
    Recent advances in collisional effects on spectra of molecular gases and their practical consequences2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 213, s. 178-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We review progress, since publication of the book "Collisional effects on molecular spectra: Laboratory experiments and models, consequences for applications" (Elsevier, Amsterdam, 2008), on measuring, modeling and predicting the influence of pressure (ie of intermolecular collisions) on the spectra of gas molecules. We first introduce recently developed experimental techniques of high accuracy and sensitivity. We then complement the above mentioned book by presenting the theoretical approaches, results and data proposed (mostly) in the last decade on the topics of isolated line shapes, line-broadening and -shifting, line-mixing, the far wings and associated continua, and collision-induced absorption. Examples of recently demonstrated consequences of the progress in the description of spectral shapes for some practical applications (metrology, probing of gas media, climate predictions) are then given. Remaining issues and directions for future research are finally discussed.

  • 23.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Shanxi University, Taiyuan 030006, China.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – II: experimental verification2016Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, s. 245-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is normally described by an expression, here termed the conventional (CONV) description, that is restricted to the conventional cavity-limited weak absorption condition (CCLWA), i.e. when the single pass absorbance is significantly smaller than the empty cavity losses, i.e. when α0L<<π/F. To describe NICE-OHMS signals beyond this limit two simplified extended descriptions (termed the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT), which are assumed to be valid under the relaxed cavity-limited weak absorption condition (RCLWA), i.e. when α0L<π/Fα0L<π/F, and a full description (denoted FULL), presumed to be valid also when the α0L<π/Fα0L<π/F condition does not hold, have recently been derived in an accompanying work (Ma W, et al. Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition - I. Theoretical Description. J Quant Spectrosc Radiat Transfer, 2015, http://dx.doi.org/10.1016/j.jqsrt.2015.09.007, this issue). The present work constitutes an experimental verification and assessment of the validity of these, performed in the Doppler limit for a set of Fα0L/πFα0L/π values (up to 3.5); it is shown under which conditions the various descriptions are valid. It is concluded that for samples with Fα0L/πFα0L/π up to 0.01, all descriptions replicate the data well. It is shown that the CONV description is adequate and provides accurate assessments of the signal strength (and thereby the analyte concentration) up to Fα0L/πFα0L/π of around 0.1, while the ELET is accurate for Fα0L/πFα0L/π up to around 0.3. The ELFT description mimics the Db NICE-OHMS signal well for Fα0L/πFα0L/π up to around unity, while the FULL description is adequate for all Fα0L/πFα0L/π values investigated. Access to these descriptions both increases considerably the dynamic range of the technique and facilitates calibration using certified reference gases, which thereby significantly broadens the applicability of the Db NICE-OHMS technique.

  • 24.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhao, Gang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Depletion of the vibrational ground state of CH4 in absorption spectroscopy at 3.4 μm in N2 and air in the 1-100Torr range2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 205, s. 59-70Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model presented in an accompanying work predicts that mid-IR absorption signals from methane in trace concentrations in various buffer gases detected at pressures in the 1-100Torr range can be reduced and distorted due to depletion of the vibrational ground state if the molecules are exposed to laser powers in the tens of mW range or above. This work provides experimental evidence of such depletion in a resonant cavity under a variety of conditions, e.g. for intracavity laser powers up to 2W and for buffer gases of N-2 or dry air, and verifies the applicability of the model. It was found that the degree of depletion is significantly larger in N-2 than dry air, and that it increases with pressure for pressures up to around 10Torr (attributed to a decreased diffusion rate) but decreases with pressure for pressures above 20Torr (caused by an increased collisional vibrational decay rate). The maximum degree of depletion (similar to 80%) was obtained for methane in N-2 at around 15Torr. This implies that absorption spectrometry of methane can experience significant non-linear dependencies on laser power, pressure, as well as buffer gas composition. It is shown that depletion takes place also in (CH4)-C-13, which verifies the applicability of the model also for this isotopologue, and that NICE-OHMS signals detected in absorption phase are less affected by depletion than in dispersion. It was concluded that the absorption mode of detection can provide concentration assessments that are virtually free of influence of depletion for intracavity powers below 0.8 W. 

  • 25.
    Hjältén, Adrian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sadiek, Ibrahim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany.
    Line positions and intensities of the ν1 band of 12CH3I using mid-infrared optical frequency comb Fourier transform spectroscopy2023Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 306, artikkel-id 108646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a new spectral analysis of the ν1 and ν3+ν1−ν3 bands of 12CH3I around 2971 cm−1 based on a high-resolution spectrum spanning from 2800 cm–1 to 3160 cm–1, measured using an optical frequency comb Fourier transform spectrometer. From this spectrum, we previously assigned the ν4 and ν3+ν4−ν3 bands around 3060 cm–1 using PGOPHER, and the line list was incorporated in the HITRAN database. Here, we treat the two fundamental bands, ν1 and ν4, together with the perturbing states, 2ν2+ν3 and ν2+2ν6±2, as a four-level system connected via Coriolis and Fermi interactions. A similar four-level system is assumed to connect the two ν3+ν1−ν3 and ν3+ν4−ν3 hot bands, which appear due to the population of the low-lying ν3 state at room temperature, with the 2ν2+2ν3 and ν2+ν3+2ν6±2 perturbing states. This spectroscopic treatment provides a good global agreement of the simulated spectra with experiment, and hence accurate line lists and band parameters of the four connected vibrational states in each system. It also allows revisiting the analysis of the ν4 and ν3+ν4−ν3 bands, which were previously treated as separate bands, not connected to their ν1 and ν3+ν1−ν3 counterparts. Overall, we assign 4665 transitions in the fundamental band system, with an average error of 0.00071 cm–1, a factor of two better than earlier work on the ν1 band using conventional Fourier transform infrared spectroscopy. The ν1 band shows hyperfine splitting, resolvable for transitions with J ≤ 2 × K. Finally, the spectral intensities of 65 lines of the ν1 band and 7 lines of the ν3+ν1−ν3 band are reported for the first time using the Voigt line shape as a model in multispectral fitting. The reported line lists and intensities will serve as a reference for high-resolution molecular spectroscopic databases, and as a basis for line selection in future monitoring applications of CH3I.

    Fulltekst (pdf)
    fulltext
  • 26.
    Hjältén, Adrian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Germann, Matthias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Tomaszewska, Dorota
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical frequency comb Fourier transform spectroscopy of 14N216O at 7.8 µm2021Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 271, artikkel-id 107734Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use a Fourier transform spectrometer based on a compact mid-infrared difference frequency generation comb source to perform broadband high-resolution measurements of nitrous oxide, 14N216O, and retrieve line center frequencies of the ν1 fundamental band and the ν1 + ν2 – ν2 hot band. The spectrum spans 90 cm−1 around 1285 cm−1 with a sample point spacing of 3 × 10−4 cm−1 (9 MHz). We report line positions of 72 lines in the ν1 fundamental band between P(37) and R(38), and 112 lines in the ν1 + ν2 – ν2 hot band (split into two components with e/f rotationless parity) between P(34) and R(33), with uncertainties in the range of 90-600 kHz. We derive upper state constants of both bands from a fit of the effective ro-vibrational Hamiltonian to the line center positions. For the fundamental band, we observe excellent agreement in the retrieved line positions and upper state constants with those reported in a recent study by AlSaif et al. using a comb-referenced quantum cascade laser [J Quant Spectrosc Radiat Transf, 2018;211:172-178]. We determine the origin of the hot band with precision one order of magnitude better than previous work based on FTIR measurements by Toth [http://mark4sun.jpl.nasa.gov/n2o.html], which is the source of the HITRAN2016 data for these bands.

    Fulltekst (pdf)
    fulltext
  • 27.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Optimised frequency grids for infrared radiative transfer simulations in cloudy conditions2012Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, nr 16, s. 2124-2134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper shows that radiometer channel radiances for cloudy atmospheric conditions can be simulated with an optimised frequency grid derived under clear-sky conditions. A new clear-sky optimised grid is derived for AVHRR channel . For HIRS channel 11 and AVHRR channel 5, radiative transfer simulations using an optimised frequency grid are compared with simulations using a reference grid, where the optimised grid has roughly 100–1000 times less frequencies than the full grid. The root mean square error between the optimised and the reference simulation is found to be less than 0.3 K for both comparisons, with the magnitude of the bias less than 0.03 K. The simulations have been carried out with the radiative transfer model Atmospheric Radiative Transfer Simulator (ARTS), version 2, using a backward Monte Carlo module for the treatment of clouds. With this module, the optimised simulations are more than 10 times faster than the reference simulations. Although the number of photons is the same, the smaller number of frequencies reduces the overhead for preparing the optical properties for each frequency. With deterministic scattering solvers, the relative decrease in runtime would be even more. The results allow for new radiative transfer applications, such as the development of new retrievals, because it becomes much quicker to carry out a large number of simulations. The conclusions are applicable to any downlooking infrared radiometer.

  • 28.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Electromagnetic scattering by nonspherical particles: Recent advances2010Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, nr 11, s. 1788-1790Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This note gives a short introduction to the reprint of the article "Numerical methods in electromagnetic scattering theory" by Kahnert, M (JQSRT 2003:79-80:775-824). Some of the most important developments in the field since the publication of this article are briefly reviewed. A list of typos that have been identified in the original article is given in the appendix. (C) 2009 Elsevier Ltd. All rights reserved.

  • 29.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Modelling radiometric properties of inhomogeneous mineral dust particles: Applicability and limitations of effective medium theories2015Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 152, s. 16-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of inhomogeneous mineralogical composition on the optical properties of mineral dust particles is investigated. More specifically, spheres composed of a non-absorbing mineral with multiple spherical hematite inclusions are considered. The size of the particles, the number of inclusions, and the hematite volume fraction are varied, and the differential and integral optical properties are compared to those computed for homogeneous spheres. The effective refractive index of the homogeneous spheres is obtained (i) by use of four conventional effective medium approximations; and (ii) by freely varying the real and imaginary parts of the refractive index until a best-fit of the scattering matrix elements is achieved for all scattering angles and particle sizes. Among the integral radiometric observables, the single scattering albedo is most sensitive to particle inhomogeneity, while the extinction and scattering efficiency and the asymmetry parameter are rather insensitive. The phase function, the degree of linear polarisation, the linear depolarisation, and, indeed, all elements of the scattering matrix are strongly modulated by particle inhomogeneity. None of the effective medium approaches, not even the best-fit method, are able to reproduce the single scattering albedo and the scattering matrix elements over the entire range of particle sizes. (C) 2014 Elsevier Ltd. All rights reserved.

  • 30.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Numerical solutions of the macroscopic Maxwell equations for scattering by non-spherical particles: A tutorial review2016Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 178, s. 22-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Numerical solution methods for electromagnetic scattering by non-spherical particles comprise a variety of different techniques, which can be traced back to different assumptions and solution strategies applied to the macroscopic Maxwell equations. One can distinguish between time- and frequency-domain methods; further, one can divide numerical techniques into finite-difference methods (which are based on approximating the differential operators), separation-of-variables methods (which are based on expanding the solution in a complete set of functions, thus approximating the fields), and volume integral-equation methods (which are usually solved by discretisation of the target volume and invoking the long-wave approximation in each volume cell). While existing reviews of the topic often tend to have a target audience of program developers and expert users, this tutorial review is intended to accommodate the needs of practitioners as well as novices to the field. The required conciseness is achieved by limiting the presentation to a selection of illustrative methods, and by omitting many technical details that are not essential at a first exposure to the subject. On the other hand, the theoretical basis of numerical methods is explained with little compromises in mathematical rigour; the rationale is that a good grasp of numerical light scattering methods is best achieved by understanding their foundation in Maxwell's theory. (C) 2015 Elsevier Ltd. All rights reserved.

  • 31.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    The T-matrix code Tsym for homogeneous dielectric particles with finite symmetries2013Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 123, s. 62-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A T-matrix code tailored to non-axisymmetric particles with finite symmetries is described. The code exploits geometric symmetries of particles by use of group theoretical methods. Commutation relations of the T-matrix are implemented for reducing CPU-time requirements. Irreducible representations of finite groups are employed for alleviating ill-conditioning problems in numerical computations. Further, an iterative T-matrix method for particles with small-scale surface perturbations is implemented. The code can compute both differential and integrated optical properties of particles in,either fixed or random orientation. Methods for testing the convergence and correctness of the computational results are discussed. The package also includes a database of pre-computed group-character tables, as well as an interface to the GAP programming language for computational group theory. The code can be downloaded at http://www.rss.chalmers.se/similar to kahnert/Tsym.html. (C) 2013 Elsevier Ltd. All rights reserved.

  • 32.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    T-matrix computations for particles with high-order finite symmetries2013Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 123, s. 79-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of group theoretical methods can substantially reduce numerical ill-conditioning problems in T-matrix computations. There are specific problems related to obtaining the irreducible characters of high-order symmetry groups and to the construction of a transformation from the basis of vector spherical wave functions to the irreducible basis of high-order symmetry groups. These problems are addressed, and numerical solutions are discussed and tested. An important application of the method is non-convex particles perturbed with high-order polynomials. Such morphologies can serve as models for particles with small-scale surface roughness, such as mineral aerosols, atmospheric ice particles with rimed surfaces, and various types of cosmic dust particles. The method is tested for high-order 3D-Chebyshev particles, and the performance of the method is gauged by comparing the results to computations based on iteratively solving a Lippmann-Schwinger T-matrix equation. The latter method trades ill-conditioning problems for potential slow-convergence problems, and it is rather specific, as it is tailored to particles with small-scale surface roughness. The group theoretical method is general and not plagued by slow-convergence problems. The comparison of results shows that both methods achieve a comparable numerical stability. This suggests that for particles with high-order symmetries the group-theoretical approach is able to overcome the illconditioning problems. Remaining numerical limitations are likely to be associated with loss-of-precision problems in the numerical evaluation of the surface integrals. (C) 2012 Elsevier Ltd. All rights reserved.

  • 33.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kanngiesser, Franz
    Modelling optical properties of atmospheric black carbon aerosols2020Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 244, artikkel-id UNSP 106849Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    fulltext
  • 34.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Meteorologi.
    Kanngiesser, Franz
    Optical properties of marine aerosol: modelling the transition from dry, irregularly shaped crystals to brine-coated, dissolving salt particles2023Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 295, artikkel-id 108408Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    Optical properties of marine aerosol: modelling the transition from dry, irregularly shaped crystals to brine-coated, dissolving salt particles
  • 35.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kanngiesser, Franz
    Jarvinen, Emma
    Schnaiter, Martin
    Aerosol-optics model for the backscatter depolarisation ratio of mineral dust particles2020Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 254, artikkel-id 107177Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The size-dependence of the linear depolarisation ratio of mineral dust aerosols is investigated. Laboratory measurements on 131 different aerosol samples with varying size distributions and mineralogical compositions are fitted with a homogeneous spheroid model. A minimum-bias and minimum-variance fit of the data is obtained for prolate model particles with a refractive index of 1.525+0.001i and an aspect ratio of 0.87. The model error is analysed by varying the input parameters to the light-scattering computations. It is found that the scattering of the measurements about the model can mainly be explained by variation of the morphology and dielectric properties, and to a much lesser extent by variation in the geometric standard deviation of the size distribution. The modelling of the data is extended by using size-shape distributions of spheroids. The results indicate that there is some freedom in choosing the best-fit weights of the shape-distribution of spheroids, which could potentially be useful when extending the model to multiple wavelengths, or to including additional optical parameters other than depolarisation. However, it is also found that the most reasonable fits of the data are obtained by mildly aspherical prolate and oblate spheroids, which limits the freedom of adjusting the best-fit weights. (C) 2020 The Authors. Published by Elsevier Ltd.

    Fulltekst (pdf)
    fulltext
  • 36.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, T
    Uncertainties in measured and modelled asymmetry parameters of mineral dust aerosols2006Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 100, nr 1-3, s. 173-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The error caused by the uncertainty in the refractive index in the determination of the asymmetry parameter g is studied for a variety of mineral dust aerosol samples at two different optical wavelengths. Lorenz-Mie computations for spherical model particles are compared with results based on laboratory-measured phase functions in conjunction with a commonly used extrapolation method. The difference between the g-value based on measurements and the g-value based on Lorenz-Mie simulations is generally on the same order of magnitude as the error caused by the uncertainty in the refractive index m. For larger effective radii the error in g related to the use of spherical model particles is even larger than that related to the uncertainty in in. This indicates that the use of spherical model particles can be among the major error sources in the determination of the asymmetry parameter of dust aerosols. (c) 2005 Elsevier Ltd. All rights reserved.

  • 37.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, Timo
    Variational data-analysis method for combining laboratory-measured light-scattering phase functions and forward-scattering computations2007Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 103, nr 1, s. 27-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method is developed based on the variational data-analysis formalism to combine laboratory-measured scattering phase functions with forward-scattering phase function computations based on independent size distribution (SD) measurements. The algorithm yields an optimal estimate of the true phase function of the system that is not only based on the measurements and the computational results but also on all available information of the error variances and, if applicable, error covariances of the measured and computed phase functions. The high flexibility of the method is demonstrated by applying it to phase functions of feldspar and fly ash aerosols. Further, the algorithm is employed to determine the asymmetry parameter g of nine different mineral aerosol samples at two different optical wavelengths, and to assess the relative importance of different error sources in the determination of g. It is found that the use of spherical model particles in simulations of g can result in errors on the same order of magnitude as the uncertainty of the refractive index. The use of spherical model particles in computations of forward scattering, however, is found to be only a minor error source. (c) 2006 Elsevier Ltd. All rights reserved.

  • 38.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, Timo
    Lindqvist, Hannakaisa
    Review: Model particles in atmospheric optics2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 146, s. 41-58Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    This review paper provides an overview over model geometries for computing light scattering by small particles. The emphasis is on atmospheric optics, although much of this review will also be relevant to neighbouring fields, in particular to astronomy. Various morphological particle properties are discussed, such as overall nonsphericity, pristine shapes, aggregation, and different forms of inhomogeneity, e.g. porous and compact inhomogeneous morphologies, as well as encapsulated aggregates. Models employed to reproduce the optical properties of complex particles range from strongly simplified to highly realistic and morphologically sophisticated model geometries. Besides reviewing the most recent literature, we discuss the idea behind models of varying degree of complexity with regard to the intended use of the models. Applications range from fundamental studies of light scattering processes to routine applications of particle optics look-up tables in operational modelling systems. (C) 2014 Elsevier Ltd. All rights reserved.

  • 39.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, Timo
    Mauno, Paivi
    On the impact of non-sphericity and small-scale surface roughness on the optical properties of hematite aerosols2011Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, nr 11, s. 1815-1824Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We perform a comparative modelling study to investigate how different morphological features influence the optical properties of hematite aerosols. We consider high-order Chebyshev particles as a proxy for aerosol with a small-scale surface roughness, and spheroids as a model for nonspherical aerosols with a smooth boundary surface. The modelling results are compared to those obtained for homogeneous spherical particles. It is found that for hematite particles with an absorption efficiency of order unity the difference in optical properties between spheres and spheroids disappears. For optically softer particles, such as ice particles at far-infrared wavelengths, this effect can be observed for absorption efficiencies lower than unity. The convergence of the optical properties of spheres and spheroids is caused by absorption and quenching of internal resonances inside the particles, which depend both on the imaginary part of the refractive index and on the size parameter, and to some extent on the real part of the refractive index. By contrast, small-scale surface roughness becomes the dominant morphological feature for large particles. This effect is likely to depend on the amplitude of the surface roughness, the relative significance of internal resonances, and possibly on the real part of the refractive index. The extinction cross section is rather insensitive to surface roughness, while the single-scattering albedo, asymmetry parameter, and the Mueller matrix are strongly influenced. Small-scale surface roughness reduces the backscattering cross section by up to a factor of 2-3 as compared to size-equivalent particles with a smooth boundary surface. This can have important implications for the interpretation of lidar backscattering observations. (C) 2011 Elsevier Ltd. All rights reserved.

  • 40.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, Timo
    Mauno, Paivi
    On the impact of non-sphericity and small-scale surface roughness on the optical properties of hematite aerosols (vol 112, pg 1815, 2011)2012Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, nr 1, s. 117-117Artikkel i tidsskrift (Fagfellevurdert)
  • 41.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Nousiainen, Timo
    Thomas, Manu Anna
    SMHI, Forskningsavdelningen, Luftmiljö.
    Tyynela, Jani
    Light scattering by particles with small-scale surface roughness: Comparison of four classes of model geometries2012Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, nr 18, s. 86-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compare four different model geometries for particles with small-scale surface roughness. The geometries are based on regular and stochastic surface perturbations, as well as on 2D- and 3D-roughness models. We further compare T-matrix and discrete dipole computations. Particle size parameters of 5 and 50 are considered, as well as refractive indices of 1.6+0.0005i and 3+0.1i. The effect of small-scale surface roughness on the intensity and polarisation of the scattered light strongly depends on the size parameter and refractive index. In general, 2D surface roughness models predict stronger effects than 3D models. Stochastic surface roughness models tend to predict the strongest depolarising effects, while regular surface roughness models can have a stronger effect on the angular distribution of the scattered intensity. Computations with the discrete dipole approximation only cover a limited range of size parameters. T-matrix computations allow us to significantly extend that range, but at the price of restricting the model particles to symmetric surface perturbations with small amplitudes. (C) 2012 Elsevier Ltd. All rights reserved.

  • 42.
    Kahnert, Michael
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Sandvik, Anne Dagrun
    Biryulina, Marina
    Stamnes, Jakob J.
    Stamnes, Knut
    Impact of ice particle shape on short-wave radiative forcing: A case study for an arctic ice cloud2008Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, nr 7, s. 1196-1218Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We used four different non-spherical particle models to compute optical properties of an arctic ice cloud and to simulate corresponding cloud radiative forcings and fluxes. One important finding is that differences in cloud forcing, downward flux at the surface, and absorbed flux in the atmosphere resulting from the use of the four different ice cloud particle models are comparable to differences in these quantities resulting from changing the surface albedo from 0.4 to 0.8, or by varying the ice water content (IWC) by a factor of 2. These findings show that the use of a suitable non-spherical ice cloud particle model is very important for a realistic assessment of the radiative impact of arctic ice clouds. The differences in radiative broadband fluxes predicted by the four different particle models were found to be caused mainly by differences in the optical depth and the asymmetry parameter. These two parameters were found to have nearly the same impact on the predicted cloud forcing. Computations were performed first by assuming a given vertical profile of the particle number density, then by assuming a given profile of the IWC. In both cases, the differences between the cloud radiative forcings computed with the four different non-spherical particle models were found to be of comparable magnitude. This finding shows that precise knowledge of ice particle number density or particle mass is not sufficient for accurate prediction of ice cloud radiative forcing. It is equally important to employ a non-spherical shape model that accurately reproduces the ice particle's dimension-to-volume ratio and its asymmetry parameter. The hexagonal column/plate model with air-bubble inclusions seems to offer the highest degree of flexibility. (c) 2007 Elsevier Ltd. All rights reserved.

  • 43. Kanngiesser, Franz
    et al.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Calculation of optical properties of light-absorbing carbon with weakly absorbing coating: A model with tunable transition from film-coating to spherical-shell coating2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 216, s. 17-36Artikkel i tidsskrift (Fagfellevurdert)
  • 44.
    Kratz, David P.
    et al.
    Radiation and Aerosols Branch, NASA Langley Research Center, Hampton.
    Mlynczak, Martin G.
    Radiation and Aerosols Branch, NASA Langley Research Center, Hampton.
    Mertens, Christopher J.
    Radiation and Aerosols Branch, NASA Langley Research Center, Hampton.
    Brindley, Helen
    Space and Atmospheric Physics Group, Imperial College of Science, Technology and Medicine, London.
    Gordley, Larry L.
    G & A Technical Software, Inc., Hampton.
    Martin-Torres, Javier
    Analytical Services and Materials Inc., Hampton.
    Miskolczi, Ferenc M.
    Analytical Services and Materials Inc., Hampton.
    Turner, David D.
    Pacific Northwest National Laboratory , Richland, WA.
    An inter-comparison of far-infrared line-by-line radiative transfer models2005Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 90, nr 3-4, s. 323-341Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A considerable fraction (>40%) of the outgoing longwave radiation escapes from the Earth's atmosphere-surface system within a region of the spectrum known as the far-infrared (wave-numbers less than ). Dominated by the line and continuum spectral features of the pure rotation band of water vapor, the far-infrared has a strong influence upon the radiative balance of the troposphere, and hence upon the climate of the Earth. Despite the importance of the far-infrared contribution, however, very few spectrally resolved observations have been made of the atmosphere for wave-numbers less than . The National Aeronautics and Space Administration (NASA), under its Instrument Incubator Program (IIP), is currently developing technology that will enable routine, space-based spectral measurements of the far-infrared. As part of NASA's IIP, the Far-Infrared Spectroscopy of the Troposphere (FIRST) project is developing an instrument that will have the capability of measuring the spectrum over the range from 100 to at a resolution of . To properly analyze the data from the FIRST instrument, accurate radiative transfer models will be required. Unlike the mid-infrared, however, no inter-comparison of codes has been performed for the far-infrared. Thus, in parallel with the development of the FIRST instrument, an investigation has been undertaken to inter-compare radiative transfer models for potential use in the analysis of far-infrared measurements. The initial phase of this investigation has focused upon the inter-comparison of six distinct line-by-line models. The results from this study have demonstrated remarkably good agreement among the models, with differences being of order 0.5%, thereby providing a high measure of confidence in our ability to accurately compute spectral radiances in the far-infrared.

  • 45.
    Kuhn, Thomas
    et al.
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    Bauer, A.
    Laboratoire de Physique des Lasers, Atomes et Molécules, Unité Mixte de Recherche CNRS, Université des Sciences et Technologies de Lille, CERLA, Villeneuve d’Ascq Cedex, France.
    Godon, M.
    Laboratoire de Physique des Lasers, Atomes et Molécules, Unité Mixte de Recherche CNRS, Université des Sciences et Technologies de Lille, CERLA, Villeneuve d’Ascq Cedex, France.
    Buehler, Stefan
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    Kuenzi, K.
    Institute of Environmental Physics, University of Bremen, Bremen, Germany.
    Water vapor continuum: absorption measurements at 350 Ghz and model calculations2002Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 74, nr 5, s. 545-562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the laboratory at 350 GHz. The dependence on pressure and temperature has been obtained. Additionally, a water vapor continuum parameter estimation, taking even the previous laboratory measurements from 150 to 350 GHz into account, is performed.

    Fulltekst (pdf)
    fulltext
  • 46.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator ARTS2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 133, s. 445-453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents the practical theory that was used to implement the Zeeman effect using Stokes formalism in the Atmospheric Radiative Transfer Simulator ARTS. ARTS now treats the Zeeman effect in a general manner for several gas species for all polarizations and takes into account variations in both magnetic and atmospheric fields along a full 3D geometry. We present how Zeeman splitting affects polarization in radiative transfer simulations and find that the effect may be large in Earth settings for polarized receivers in limb observing geometry. We find that not taking a spatially varying magnetic field into account can result in absolute errors in the measurement vector of at least 10 K in Earth magnetic field settings. The article also presents qualitative tests for O2 lines against previous models (61.15 GHz line) and satellite data from Odin-SMR (487.25 GHz line), and the overall consistency between previous models, satellite data, and the new ARTS Zeeman module seems encouraging.

  • 47.
    López-Puertas, M.
    et al.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Zaragoza, G.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    López-Valverde, M.Á.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Martin-Torres, Javier
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Shved, G.M.
    Institute of Physics, University of St. Petersburg.
    Manuilova, R.O.
    Institute of Physics, University of St. Petersburg.
    Kutepov, A.A.
    Institut für Astronomie und Astrophysik der Universität München.
    Gusev, O.A.
    Institut für Astronomie und Astrophysik der Universität München.
    Von Clarmann, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Stiller, G.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Wegner, A.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Oelhaf, H.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Edwards, D.P.
    National Center for Atmospheric Research, Boulder, Colorado.
    Flaud, J.-M.
    Université Pierre et Marie Curie (UPMC), Paris.
    Non-local thermodynamic equilibrium limb radiances for the mipas instrument on Envisat-11998Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 59, nr 3-5, s. 377-403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An evaluation of the effects that the assumption of local thermodynamic equilibrium (LTE) has on the retrieval of pressure, temperature and the five primary target gases (O3, H2O, CH4, N2O, and HNO3) from spectra to be taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the Envisat-1 platform has been conducted. For doing so, non-LTE and LTE limb radiances in the spectral range of 680–2275 cm−1 (4.15–14.6 μm) with a resolution of 0.05 cm−1 at tangent heights from 10 to 70 km have been computed. These calculations included the most updated non-LTE populations of a large number of vibrational levels of the CO2, O3, H2O, CH4, N2O and HNO3 molecules which cause the most prominent atmospheric infrared emissions. A discussion of the most important non-LTE effects on the limb radiances as well as on the retrievals of pressure-temperature and volume mixing ratios of O3, H2O, CH4, N2O, and HNO3 is presented, together with the most important non-LTE issues that could be studied with the future coming of MIPAS data.

  • 48.
    Ma, Weiguang
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – I. Theoretical Description2016Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, s. 217-244Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is conventionally described by an expression (here referred to as the CONV expression) that is restricted to the case when the single-pass absorbance, α0L, is much smaller than the empty cavity losses, π/F [here termed the conventional cavity-limited weak absorption (CCLWA) condition]. This limits the applicability of the technique, primarily its dynamic range and calibration capability. To remedy this, this work derives extended descriptions of Db NICEOHMS that are not restricted to the CCLWA condition. First, the general principles of Db NICEOHMS are scrutinized in some detail. Based solely upon a set of general assumptions, predominantly that it is appropriate to linearize the Beer–Lambert law, that the light is modulated to a triplet, and that the Pound–Drever–Hall sidebands are fully reflected, a general description of Db NICE-OHMS that is not limited to any specific restriction on α0L vs. π/F, here referred to as the FULL description, is derived. However, this description constitutes a set of equations to which no closed form solution has been found. Hence, it needs to be solved numerically (by iterations), which is inconvenient. To circumvent this, for the cases when α0Loπ/F but without the requirement that the stronger CCLWA condition needs to be fulfilled, a couple of simplified extended expressions that are expressible in closed analytical form, referred to as the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT, have been derived. An analysis based on simulations validates the various descriptions and assesses to which extent they agree. It is shown that in the CCLWA limit, all extended descriptions revert to the CONV expression. The latter one deviates though from the extended ones for α0L around and above 0.1π/F. The two simplified extended descriptions agree with the FULL description for a larger range of α0L than the CONV expression, viz. for the ELET description for α0L up to 0.3π/F and for ELFT for α0L up to 0.6 or 1.0 π/F (depending on the mode of detection). It is then demonstrated that the conventional view of Db NICE-OHMS, which states that the out-of-phase and the in-phase signals can be referred to as a pure absorption and dispersion signal, respectively, breaks down when the CCLWA condition does not hold. In this case, the out-of-phase signal is additionally affected by the phase shifts of the laser components (i.e. dispersion) while the in-phase signal is also influenced by their attenuation. Access to new descriptions broadens considerably the dynamic range of Db NICE-OHMS and facilitates calibration using standard references samples, and thereby its applicability

  • 49. Mackowski, D. W.
    et al.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Mishchenko, M. I.
    A T matrix method based upon scalar basis functions2013Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 123, s. 113-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A surface integral formulation is developed for the T matrix of a homogenous and isotropic particle of arbitrary shape, which employs scalar basis functions represented by the translation matrix elements of the vector spherical wave functions. The formulation begins with the volume integral equation for scattering by the particle, which is transformed so that the vector and dyadic components in the equation are replaced with associated dipole and multipole level scalar harmonic wave functions. The approach leads to a volume integral formulation for the T matrix, which can be extended, by the use of Green's identities, to the surface integral formulation. The result is shown to be equivalent to the traditional surface integral formulas based on the VSWF basis. (C) 2013 Elsevier Ltd. All rights reserved.

  • 50.
    Manuilova, R.O.
    et al.
    Department of Atmospheric Physics, University of St. Petersburg.
    Gusev, O.A.
    Institut für Astronomie und Astrophysik der Universität München.
    Kutepov, A.A.
    Institut für Astronomie und Astrophysik der Universität München.
    Von Clarmann, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Oelhaf, H.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Stiller, G.P.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Wegner, A.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    López-Puertas, M.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Martin-Torres, Javier
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Zaragoza, G.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Flaud, J.-M.
    Laboratoire de Photophysique Moléculaire, CNRS, Université Paris-Sud, Orsay.
    Modelling of non-LTE limb spectra of i.r. ozone bands for the MIPAS space experiment1998Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 59, nr 3-5, s. 405-422Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new model for calculating the populations of the ozone vibrational states under non-LTE (Local Thermodynamic Equilibrium) conditions is presented. In the model, 23 vibrational levels of the O3 molecule, as well as three vibrational levels of the O2 molecule and two vibrational levels of the N2 molecule, are considered. The radiative transfer at the break-down of LTE was treated explicitly for 150 000 ro-vibrational transitions. The populations obtained were used to calculate limb radiances in various spectral regions of the 4.8 and 9.6 μm bands. Test retrievals of O3 vertical volume mixing ratio (VMR) profiles with a radiance model disregarding non-LTE were performed in order to assess the potential impact of non-LTE effects on the retrieval of the O3 abundances from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) measurements.

12 1 - 50 of 94
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf