Radiative transfer simulations using mesoscale cloud model outputs : Comparisons with passive microwave and infrared satellite observations for midlatitudes

• Published in: Journal of the atmospheric sciences Vol. 64; no. 5; pp. 1550 - 1568
• Main Authors: MEIROLD-MAUTNER, Ingo, PRIGENT, Catherine, DEFER, Eric, PARDO, Juan R, CHABOUREAU, Jean-Pierre, PINTY, Jean-Pierre, MECH, Mario, CREWELL, Susanne
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.05.2007
• Subjects: Atmospheric models; Clouds; Earth, ocean, space; Electrical properties; Exact sciences and technology; External geophysics; Meteorology; Physics of the high neutral atmosphere; Radiation; Radiative transfer; Snow; Western Europe; Europe; models; Mid latitude; atmospheric precipitation; Europe; Space remote sensing; Infrared observation; dielectric properties; Large scale structure; Satellite observation; ice; clouds; Mesoscale; brightness temperature; s parameter; Dipole approximation; snow; Particle scattering; Radiative transfer; Microwave radiometry; Hydrometeor
• ISSN: 0022-4928; 1520-0469
• DOI: 10.1175/JAS3896.1

Real midlatitude meteorological cases are simulated over western Europe with the cloud mesoscale model Meso-NH, and the outputs are used to calculate brightness temperatures at microwave frequencies with the Atmospheric Transmission at Microwave (ATM) radiative transfer model. Satellite-observed brightness temperatures (TBs) from the Advanced Microwave Scanning Unit B (AMSU-B) and the Special Sensor Microwave Imager (SSM/I) are compared to the simulated ones. In this paper, one specific situation is examined in detail. The infrared responses have also been calculated and compared to the Meteosat coincident observations. Overall agreement is obtained between the simulated and the observed brightness temperatures in the microwave and in the infrared. The large-scale dynamical structure of the cloud system is well captured by Meso-NH. However, in regions with large quantities of frozen hydrometeors, the comparison shows that the simulated microwave TBs are higher than the measured ones in the window channels at high frequencies, indicating that the calculation does not predict enough scattering. The factors responsible for the scattering (frozen particle distribution, calculation of particle dielectric properties, and nonsphericity of the particles) are analyzed. To assess the quality of the cloud and precipitation simulations by Meso-NH, the microphysical fields predicted by the German Lokal-Modell are also considered. Results show that in these midlatitude situations, the treatment of the snow category has a high impact on the simulated brightness temperatures. The snow scattering parameters are tuned to match the discrete dipole approximation calculations and to obtain a good agreement between simulations and observations even in the areas with significant frozen particles. Analysis of the other meteorological simulations confirms these results. Comparing simulations and observations in the microwave provides a powerful evaluation of resolved clouds in mesoscale models, especially the precipitating ice phase. [PUBLICATION ABSTRACT]