Interaction at mm and optical frequencies. Pt. 2 Specific atmospheric absorption and emission features: Investigation and modelling. Final report

This study deals with: Numerical analysis of the accuracy of recent models for atmospheric molecular absorption, in particular, studies of line mixing, line narowing (Dicke effect) and line shift effects; Establishment of a radiative transfet code for the computation of non-LTE outgoing radiation in the infrared spectrum; Analysis of up-to-date accuracy of initial spectroscopic information and its influence on outgoing radiation calculations in different spectral domains; Numerical investigations of the errors due to calculations of transmittance and outgoing radiation by k-distribution method. The investigations performed permit a more accurate estimate of up-to-date methods and algorithms for the calculation of atmospheric radiative transfer and to supply enhanced radiative transfer codes. (orig./KW)SIGLEAvailable from TIB Hannover: RR 1857(18) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekEuropean Space Agency (ESA), 75 - Paris (France)DEGerman

Interaction at mm and optical frequencies. Pt. 1 Current problems in radiative transfer simulations. Final report

An extensive literature survey of recent developments in the field of radiative transfer has been done. Within the scope of plane-parallel solutions of the RTE several solution methods have been presented: E.g. spherical harmonics, discrete ordinates, adding, doubling, matrix-operator, finite difference, and Gauss Seidel iteration. Solutions of the vector RTE permitting to take into account polarization and the subject of multidimensional geometry have been examined. General information and some models commonly used for solving the spherical RTE are presented. The subjects of RTM at millimetre wavelengths and the state of considering non-LTE effects has been reviewed. Models for the purpose of spectral integration have been discussed: GOMETRAN, LOWTRAN, MODTRAN, FASCOD-3, GENLN-2, and RADTRAN. Processes in the atmosphere influencing radiative transfer have been discussed: Monochromatic molecular absorption/emission properties (line parameters, line-mixing, and Dicke effect), broadband features (if required), scattering, properties of clouds and aerosols, and the lower boundary condition. Within a review of campaigns the validation problem has been discussed. (orig./KW)SIGLEAvailable from TIB Hannover: RR 1857(17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekEuropean Space Agency (ESA), 75 - Paris (France)DEGerman

Numerical modeling of the influence of non-LTE effects on the MIPAS balloon and satellite limb radiance measurements

The report contains the results of investigations performed in frame of Cooperation Agreement for 1993-1995 between the Institut fuer Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, and the Research Institute of Physics at St. Petersburg State University, Russia. Several atmospheric models and computer codes, which describe the non-LTE (non-local thermodynamic equilibrium) populations of vibrational states of molecules of atmospheric gases and simulate non-LTE atmospheric radiance, have been considered. The particular attention has been paid to infrared emissions by carbon dioxide, ozone, which have been measured by the MIPAS-B instrument (balloon flights) and will be measured by the MIPAS instrument during the future European Polar Platform space mission. Nitric oxide non-LTE emissions have been considered also. On the basis of the available non-LTE models and codes the influence of the non-LTE effect on the MIPAS balloon-borne and space-borne measurements has been studied, first, from the point of the detectability of the effect, and, second, regarding the retrieval of the vertical distributions of temperature and gas composition. (orig.)SIGLEAvailable from TIB Hannover: ZA 5141(5860) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Study for the intercomparison between the global fit and the optimal estimation methods in case of the limb radiance measurements

The global fit (GF) and the optimal estimation (OE) methods have been compared on the basis of simulations of limb radiance measurements by a high resolution interferometer. The simulations were close to the scenarios of the MIPAS measurements scheduled for the space mission on board the ENVISAT-1 polar platform. The advantages of the applicability of each of the mentioned methods to the interpretation of data have been investigated theoretically and on the basis of numerically simulated test retrievals. The intercomparisons have been carried out for the set of models belonging to the ensemble of atmospheric profiles of pressure, temperature, and concentrations of ozone and water vapor. The ensemble of profiles has been created on the basis of the TIGR database and atmospheric parameters retrieved from the ATMOS data. The limb radiance measurements have been modeled in the microwindows located in the CO_2, O_3, and H_2O absorption bands. The influence of the following parameters and factors on the errors of the retrieval of pressure, temperature, ozone and water vapor profiles has been estimated: random measurement noise, initial guess, a priori statistics, convergence criteria, atmospheric conditions, fine structure of profiles, finite angular resolution of measurements. The recommendations have been worked out for the utilization of the global fit and optimal estimation algorithms in the case of the MIPAS data processing. (orig.)45 refs.Available from TIB Hannover: ZA 5141(6047) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman