On constraining model microphysical processes with RICO observations

The trade-wind cumulus regions have significant impacts on both the Earth's radiation and water budget, yet the proper model representation of shallow cumulus cloud fraction and precipitation remains an on-going modeling challenge. Here we examine one aspect of the modeling challenge, namely determining the proper microphysical representation. We evaluate two commonly-used microphysical representations using observations gathered on the R/V Seward Johnson during the Rain in Cumulus over Ocean experiment. Sub-cloud vertical velocities from the ship-based Doppler lidar are used to force a one-dimensional kinematic driver, with the output from at least two microphysics schemes, the Thompson09 and the WRF double-moment 6-class (WDM-6) schemes, compared to scanning cloud radar (35 GHz) reflectivities and other RICO datasets. The emphasis is on January 19 and January 24, when precipitating and non-precipitating convection were observed on the two days respectively. Preliminary results show significant differences between the results from the two schemes, with neither scheme capturing the observed vertical distribution of cloud and rain. These will be discussed, along with the underlying sensitivities. The use of observed vertical velocities and cloud properties complements similar, more idealized efforts. Results from other microphysical schemes may also be presented.