7D.1 Numerical simulation of the 8 September 2006 MCS during AMMA: evaluation of the dynamics and microphysics using synthetic observations

Tuesday, 11 May 2010: 12:00 AM
Tucson Salon A-C (JW MArriott Starr Pass Resort)
Guillaume Penide, LAMP Laboratoire de Météorologie Physique, Aubière, France; and V. Giraud, D. Bouniol, A. Protat, C. Duroure, P. Dubuisson, and S. Cautenet

We present a numerical simulation of a Mesoscale Convective System (MCS) observed during the AMMA (African Monsoon Multidisciplinary Analyses) experiment with the BRAMS model (Brazilian Regional Atmospheric Modelling System). The aim is to document the life cycle of the MCS and to identify key cloud microphysical processes and their signatures by making use of synthetic observations calculated from the simulated fields.

These observations: ARM (Atmospheric Radiation Measurement) 95 GHz equivalent radar reflectivity factor and Doppler velocity and IR brightness temperatures in 3 SEVIRI (Spinning Enhanced Visible and Infrared Imager) channels centred at 8.7, 10.6 and 12 µm are simulated using respectively Mie scattering theory and FASDOM (Fast Discrete Ordinate Method), a fast radiative transfer code. Synthetic observations and model variables are compared to various measurements from several platforms such as ARM W-band and Massachusetts Institute of Technology (MIT) ground-based Doppler radars, soundings, aircraft measurements (french Falcon-20), and Meteosat Second Generation (MSG) to evaluate the model at different scales and to identify the microphysical signatures in the observations with a focus on the anvil part of the MCS. A method using both the ARM and the MIT radar data is used to identify the different regimes within the MCS (Convection/Stratiform/Cirriform) which permit to make consistent comparisons. A relatively good agreement with direct comparisons is found, as well as discrepancies in the microphysical scheme parameterization that clearly need improvements (notably using in-situ measurements). Microphysical signatures are also studied using joint radar reflectivity/Doppler-height histograms (also called Contoured Frequency by Altitude Diagram). The analysis of these CFADs shows that the model tends to overplay the role of the riming processes, even in the rear anvil part. Comparisons of the Particle Size Distributions (simulated and measured in-situ) show the model's ability to reproduce complex PSDs (multimodal behavior).

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