Radiative Transfer Simulations Using Mesoscale Cloud Model Outputs: Comparisons with Passive Microwave and Infrared Satellite Observations for Midlatitudes

Abstract

Real midlatitude meteorological cases are simulated over western Europe with the cloud mesoscale model Méso-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 Méso-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 Méso-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.

A high resolution climatology of precipitation and deep convection over the Mediterranean region from operational satellite microwave data: development and application to the evaluation of model uncertainties

“…In these regions, snow dominates in the atmospheric column. As previously diagnosed by Meirold-Mautner et al (2007), these discrepancies can be attributed to difficulties in accurately representing the radiative properties of snow (a mixture of air and ice particles) in the microwave region. Over the Ionian Sea where the most active cell is located, in the Meso-NH simulation, a circular pattern was predicted close to what was observed, but with a DC area underestimation.…”

The impact of the melting layer on the passive microwave cloud scattering signal observed from satellites: A study using TRMM microwave passive and active measurements

“…It is important to keep in mind that modeling the optical properties of frozen particles is problematic even for pristine frozen particles that are not undergoing melting. The particle size distribution, the dielectric properties of the material, and the shape of the particle are all subject to large uncertainties that can translate into significant differences in terms of simulated brightness temperatures [e.g., Surussavadee and Staelin, 2006;Meirold-Mautner et al, 2006;Kulie et al, 2010].…”

Verification of Hydrometeor Properties Simulated by a Cloud-Resolving Model Using a Passive Microwave Satellite and Ground-Based Radar Observations for a Rainfall System Associated with the Baiu Front

“…Given the high sensitivity of these frequencies to particle charac teristics especially for the frozen hydrometeors, this study demonstrated the accuracy of the radiative transfer model and the overall behavior of the one-moment cloud microphysical scheme for tropical deep convective cloud systems. Meirold-Mautner et al (2007) also compared radiative transfer calculations derived from Meso-NH output with satellite-observed brightness temperatures (TBs) from the Advanced Microwave Scanning Unit B (AMSU-B) and the Special Sensor Microwave Imager (SSM/I) for real mid-latitude meteorological cases over western Europe. In regions with large quantities of frozen hydrometeors, the comparison revealed that the simulated microwave TBs are higher than the measured ones in the window channels at high frequencies, indicating that the simulations did not predict enough scattering.…”