Microphysical parameters and precipitation formation in shallow cumulus clouds simulated by the LES explicit microphysics model

The LES model with explicit size-resolving microphysical formulation (SAMEX) has been used to study shallow cumulus clouds observed during the RICO (Rain in Cumulus over the Ocean) field project. The SAMEX model employs the dynamical core from the SAM model developed by M. Khairoutdinov which is combined with explicit microphysics from the CIMMS LES model. The 24 hr simulations in the 12.8x12.8 km2 domain were initialized with profiles specified for the GCSS boundary layer group RICO intercomparison study. Microphysical parameters, such as supersaturation, interstitial aerosol, cloud and rain water mixing ratios and concentrations, precipitation flux, as well as their vertical profiles, were analyzed as a function of cloud size and its stage of evolution. Substantial differences affecting precipitation formation were noted in single and multi-cell clouds. Supersaturation field in simulated RICO clouds was notably different from the one simulated in stratocumulus cloud layers using ASTEX data. Comparison with RICO observations was conducted to evaluate the ability of the explicit microphysics model to realistically reproduce drop spectra and other microphysical parameters. Implications of the findings to precipitation parameterization development will be discussed.