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  • 1. Buehler, Stefan
    et al.
    Engeln, A. von
    Universität Bremen, Institute of Environmental Physics.
    Brocard, E.
    Universität Bremen, Institute of Environmental Physics.
    John, Viju Oommen
    Universität Bremen, Institute of Environmental Physics.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. University of Köln, Physikalisches Institut.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Recent developments in the line-by-line modeling of outgoing longwave radiation2006In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 98, no 3, p. 446-457Article in journal (Refereed)
    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.

  • 2. Buehler, Stefan
    et al.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Universität Bremen, Institute of Environmental Physics.
    Engeln, Axel von
    Universität Bremen, Institute of Environmental Physics.
    Verdes, C.
    Universität Bremen, Institute of Environmental Physics.
    ARTS: the atmospheric radiative transfer simulator2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 91, no 1, p. 65-93Article in journal (Refereed)
    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.

  • 3.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lemke, Oliver
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Absorption lookup tables in the radiative transfer model ARTS2011In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, no 10, p. 1559-1567Article in journal (Refereed)
    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.

  • 4.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Kottayil, Ajil
    Milz, Mathias
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Efficient radiative transfer simulations for a broadband infrared radiometer: combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing2010In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, no 4, p. 602-615Article in journal (Refereed)
    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 University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Universität Bremen, Institute of Environmental Physics.
    Bauer, Agnes
    Institute of Environmental Physics, University of Bremen.
    Corrigendum to 'Water vapor continuum: Absorption measurements at 350 GHz and model calculations' [JQSRT 2002;74:545-62]2008In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, no 9, p. 1743-1744Article in journal (Other academic)
  • 6.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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 −Xe2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 209, p. 232-242Article in journal (Refereed)
    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.

  • 7.
    Eriksson, P.
    et al.
    Chalmers University of Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Davis, C.P.
    Meteorological Service of New Zealand.
    Emde, C.
    Meteorological Institute, Ludwig-Maximilians-Universität, Munchen.
    Lemke, Oliver
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    ARTS, the atmospheric radiative transfer simulator, version 22011In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, no 10, p. 1551-1558Article in journal (Refereed)
    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.

  • 8.
    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 work2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 91, no 1, p. 47-64Article in journal (Refereed)
    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.

  • 9.
    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 spectra2002In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 73, no 6, p. 529-543Article in journal (Refereed)
    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.

  • 10.
    Gasteiger, J.
    et al.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Emde, C.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Mayer, B.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Buras, R.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Lemke, Oliver
    Representative wavelengths absorption parameterization applied to satellite channels and spectral bands2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 148, p. 99-115Article in journal (Refereed)
    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.

  • 11.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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 consequences2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 213, p. 178-227Article in journal (Refereed)
    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.

  • 12.
    Holl, Gerrit
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kottayil, Ajil
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Optimised frequency grids for infrared radiative transfer simulations in cloudy conditions2012In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, no 16, p. 2124-2134Article in journal (Refereed)
    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.

  • 13.
    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 models2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 90, no 3-4, p. 323-341Article in journal (Refereed)
    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.

  • 14.
    Kuhn, Thomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Universität Bremen, Institute of Environmental Physics.
    Bauer, A.
    Université de Lille, Laboratoire de Physique des Lasers, atomes et molécules, Unité mixte de recherche CNRS, Villeneuve d'Ascq.
    Godon, M.
    Université de Lille, Laboratoire de Physique des Lasers, atomes et molécules, Unité mixte de recherche CNRS, Villeneuve d'Ascq.
    Buehler, Stefan
    Kuenzi, K.
    Universität Bremen, Institute of Environmental Physics.
    Water vapor continuum: absorption measurements at 350 GHz and model calculations2002In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 74, no 5, p. 545-562Article in journal (Refereed)
    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.

  • 15.
    Larsson, Richard
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator ARTS2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 133, p. 445-453Article in journal (Refereed)
    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.

  • 16.
    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.
    Clarmann, T. Von
    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-11998In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 59, no 3-5, p. 377-403Article in journal (Refereed)
    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.

  • 17.
    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.
    Clarmann, T. Von
    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 experiment1998In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 59, no 3-5, p. 405-422Article in journal (Refereed)
    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.

  • 18.
    Richard, Cyril
    et al.
    Harvard-Smithsonian Center for Astrophysics.
    Gordon, Iouli E.
    Harvard-Smithsonian Center for Astrophysics.
    Rothman, Laurence S.
    Harvard-Smithsonian Center for Astrophysics.
    Abel, Martin
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Hartmann, Jean-Michel
    Université Paris Est Créteil, CNRS.
    Hermans, Christian
    Belgian Institute for Space Aeronomy, Brussels.
    Lafferty, Walter J.
    National Institute of Standards and Technology, Gaithersburg, USA.
    Orton, Glenn S.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Smith, Kevin M.
    Rutherford Appleton Laboratory, Oxfordshire.
    Tran, Ha
    Université Paris Est Créteil, CNRS.
    New section of the HITRAN database: Collision-induced absorption (CIA)2012In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, no 11, p. 1276-1285Article in journal (Refereed)
    Abstract [en]

    This paper describes the addition of Collision-Induced Absorption (CIA) into the HITRAN compilation. The data from different experimental and theoretical sources have been cast into a consistent format and formalism. The implementation of these new spectral data into the HITRAN database is invaluable for modeling and interpreting spectra of telluric and other planetary atmospheres as well as stellar atmospheres. In this implementation for HITRAN, CIAs of N2, H2, O2, CO2, and CH4 due to various collisionally interacting atoms or molecules are presented. Some CIA spectra are given over an extended range of frequencies, including several H2 overtone bands that are dipole-forbidden in the non-interacting molecules. Temperatures from tens to thousands of Kelvin are considered, as required, for example, in astrophysical analyses of objects, including cool white dwarfs, brown dwarfs, M dwarfs, cool main sequence stars, solar and extra-solar planets, and the formation of so-called first stars.

  • 19.
    Rothman, Laurence S.
    et al.
    Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division.
    Martin-Torres, Javier
    NASA Langley Research Center, Hampton.
    Flaud, Jean Marie
    Universities of Paris 12 and 7.
    Special issue on planetary atmospheres2008In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, no 6, p. 881-Article in journal (Refereed)
  • 20.
    Sato, T. O.
    et al.
    Tokyo Institute of Technology.
    Mizoguchi, A.
    Tokyo Institute of Technology.
    Mendrok, Jana
    Kanamori, H.
    Tokyo Institute of Technology.
    Kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Measurement of the pressure broadening coefficient of the 625 GHz transition of H2O2 in the sub-millimeter-wave region2010In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, no 6, p. 821-825Article in journal (Refereed)
  • 21.
    Schreier, Franz
    et al.
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    García, Sebastián Gimeno
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Hedelt, Pascal
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Hess, Michael
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Vasquez, Mayte
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Xu, Jian
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    GARLIC - a general purpose atmospheric radiative transfer line-by-line infrared-microwave code: Implementation and evaluation2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 137, p. 29-50Article in journal (Refereed)
    Abstract [en]

    A suite of programs for high resolution infrared-microwave atmospheric radiative transfer modeling has been developed with emphasis on efficient and reliable numerical algorithms and a modular approach appropriate for simulation and/or retrieval in a variety of applications. The Generic Atmospheric Radiation Line-by-line Infrared Code — GARLIC — is suitable for arbitrary observation geometry, instrumental field–of–view, and line shape. The core of GARLIC's subroutines constitutes the basis of forward models used to implement inversion codes to retrieve atmospheric state parameters from limb and nadir sounding instruments.This paper briefly introduces the physical and mathematical basics of GARLIC and its descendants and continues with an in-depth presentation of various implementation aspects: An optimized Voigt function algorithm combined with a two-grid approach is used to accelerate the line-by-line modeling of molecular cross sections; various quadrature methods are implemented to evaluate the Schwarzschild and Beer integrals; and Jacobians, i.e. derivatives with respect to the unknowns of the atmospheric inverse problem, are implemented by means of automatic differentiation. For an assessment of GARLIC's performance, a comparison of the quadrature methods for solution of the path integral is provided. Verification and validation are demonstrated using intercomparisons with other line-by-line codes and comparisons of synthetic spectra with spectra observed on Earth and from Venus.

  • 22.
    Schreier, Franz
    et al.
    DLR, Remote Sensing Technology Institute, 82234 Oberpfaffenhofen.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan A.
    Universität Hamburg, Meteorological Institute.
    Clarmann, Thomas von
    KIT — Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research.
    Intercomparison of three microwave/infrared high resolution line-by-line radiative transfer codes2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 211, p. 64-77Article in journal (Refereed)
    Abstract [en]

    An intercomparison of three line-by-line (lbl) codes developed independently for atmospheric radiative transfer and remote sensing – ARTS, GARLIC, and KOPRA – has been performed for a thermal infrared nadir sounding application assuming a HIRS-like (High resolution Infrared Radiation Sounder) setup. Radiances for the 19 HIRS infrared channels and a set of 42 atmospheric profiles from the “Garand dataset” have been computed.

    The mutual differences of the equivalent brightness temperatures are presented and possible causes of disagreement are discussed. In particular, the impact of path integration schemes and atmospheric layer discretization is assessed. When the continuum absorption contribution is ignored because of the different implementations, residuals are generally in the sub-Kelvin range and smaller than 0.1 K for some window channels (and all atmospheric models and lbl codes). None of the three codes turned out to be perfect for all channels and atmospheres. Remaining discrepancies are attributed to different lbl optimization techniques. Lbl codes seem to have reached a maturity in the implementation of radiative transfer that the choice of the underlying physical models (line shape models, continua etc) becomes increasingly relevant.

  • 23.
    Sreerekha, T. R.
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Emde, Claudia
    Universität Bremen, Institute of Environmental Physics.
    A simple new radiative transfer model for simulating the effect of cirrus clouds in the microwave spectral region2002In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 75, no 5, p. 611-624Article in journal (Refereed)
    Abstract [en]

    The upwelling atmospheric radiation in the millimeter wave spectral range is influenced by the presence of cirrus clouds. A plane parallel radiative transfer model which can take into account the effect of multiple scattering by ice particles in the cirrus has been developed and is used to simulate the brightness temperatures as they would be measured by a satellite instrument. The model uses an iterative procedure to solve the radiative transfer equation. The formulation of the model is such that it can easily be adapted to treat the full specific intensity vector instead of just the scalar total intensity. A convergence test for the model is explained and two cirrus cloud scenarios are simulated. The results illustrate the linearity of microwave radiative transfer for not too strong cirrus clouds in this frequency region

  • 24.
    Sreerekha, T.R.
    et al.
    UK Met Office, Exeter.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    O'Keeffe, U
    UK Met Office, Exeter.
    Doherty, A
    UK Met Office, Exeter.
    Emde, C.
    German Aerospace Center, DLR, Oberpfaffenhofen.
    John, V.O.
    RSMAS, University of Miami.
    A strong ice cloud event as seen by a microwave satellite sensor: simulations and observations2008In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, no 9, p. 1705-1718Article in journal (Refereed)
    Abstract [en]

    In this article, brightness temperatures observed by channels of the Advanced Microwave Sounding Unit-B (AMSU-B) instrument are compared to those simulated by a radiative transfer model, which can take into account the multiple scattering due to ice particles by using a discrete ordinate iterative solution method. The input fields, namely, the pressure, temperature, humidity, and cloud water content are taken from the short range forecast from the Met Office mesoscale model (UKMES). The comparison was made for a case study on the 25 January 2002 when a frontal system associated with significant cloud was present over the UK. It is demonstrated that liquid clouds have maximum impact on channel 16 of AMSU whereas ice clouds have maximum impact on channel 20. The main uncertainty for simulating microwave radiances is the assumptions about microphysical properties, such as size distribution, shape and orientation of the cloud particles, which are not known in the mesoscale model. The article examines the impact of these parameters on the cloud signal. The polarisation signal due to oriented ice particles at these frequencies is also discussed.

  • 25.
    Teichmann, C.
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Emde, C.
    Deutsches Zentrum für Luft- und Raumfahrt (DLR) Institut für Physik der Atmosphäre, Wessling.
    Understanding the polarization signal of spherical particles for microwave limb radiances2006In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 10, no 1, p. 179-190Article in journal (Refereed)
    Abstract [en]

    This paper presents a simple conceptual model to explain that even spherical scatterers lead to a polarization difference signal for microwave limb radiances. The conceptual model relates the polarization difference measured by a limb-looking sensor situated inside a cloud with the anisotropy of the radiation. In the simulations, it was assumed that the cloud consists of spherical ice particles with a radius of ...

  • 26.
    Verdes, C. L.
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Engeln, Axel von
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Perrin, A.
    Universite de Paris-Sud, Orsay.
    Partition function data and impact on retrieval quality for an mm/sub-mm limb sounder2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 90, no 2, p. 217-238Article in journal (Refereed)
    Abstract [en]

    The partition function plays a major role as it mainly governs the dependence of the spectral line strength (or line intensity) on the temperature. A wrong partition function will lead to an incorrect line strength, which will lead to a systematic error in the retrieval. Therefore, a careful investigation of the available partition function data and the sensitivity of the retrieval to this is required. Two partition function data sets, the HITRAN and the JPL, are considered in this paper. In a first step, we investigate the spread of the partition function ratios from the simple approximation values given by theory. We find that the HITRAN partition functions are usually higher than the values quoted by the simple approximation. The JPL partition functions are much closer to the values given by the approximation. Comparing directly the two datasets, with some exceptions, a good agreement is found. Only for 16 molecules (from 66 considered molecules), the deviations in the two data sets are larger than 2%. The retrieval error analysis shows that, for the case of the molecular species with strong signatures, an uncertainty in the partition function is directly translated into a retrieval error of the species in question. However, the uncertainty in the partition function of this species can have a high impact on the quality of weak species retrieval.

1 - 26 of 26
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