Numerical simulation of the 7 to 9 September 2006 AMMA mesoscale convective system : Evaluation of the dynamics and cloud microphysics using synthetic observations
Penide, G. ; Giraud, V. ; Bouniol, D. ; Dubuisson, P. ; Duroure, C. ; Protat, A. ; Cautenet, S.
This paper presents a numerical simulation of a Mesoscale convective System (MCS) observed during
the AMMA (African Monsoon Multidisciplinary Analysis) experiment with the BRAMS model (Brazilian Regional<br>Atmospheric Modelling System). The aim is to document the life cycle of the MCS and to identify key cloud microphysical<br>processes and their signatures by making use of synthetic observations calculated from the simulated fields. These<br>observations: ARM (Atmospheric Radiation Measurement) 95 GHz equivalent radar reflectivity factor and Doppler velocity<br>and infrared brightness temperatures in three SEVIRI (Spinning Enhanced Visible and InfraRed Imager) channels centred<br>at 8.7, 10.6 and 12 ?m are simulated using respectively Mie scattering theory and FASDOM (Fast Discrete Ordinate<br>Method), a fast radiative transfer code. Synthetic observations and model variables are compared to various measurements<br>from several platforms (W-band and Massachusetts Institute of Technology (MIT) ground-based Doppler radars, soundings,<br>aircraft measurements, and Meteosat Second Generation) to evaluate the model at different scales and to identify the<br>signatures of microphysical properties with a focus on the anvil part of the MCS. A method using both the ARM and the MIT<br>radar data is used to identify the different regimes within the MCS. A relatively good agreement with direct comparisons<br>is found, as well as discrepancies in the microphysical scheme parametrization that clearly need improvements (using<br>in situ measurements). Microphysical signatures are also studied using joint radar reflectivity/Doppler-height histograms.<br>Their analysis shows that the model tends to overplay the role of the riming processes, even in the anvil part of the MCS.<br>Comparisons of the Particle Size Distributions (simulated and measured in situ) show the model's ability to reproduce<br>complex PSDs (e.g. a multimodal behaviour). Copyright c 2010 Royal Meteorological Society
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