SIMPLE 2-DIMENSIONAL KINEMATIC FRAMEWORK DESIGNED TO TEST WARM RAIN MICROPHYSICAL MODELS

This paper describes a two-dimensional kinematic framework designed to test warm rain microphysical models. The idealized flow field is base d on a case study from the Hawaiian Rainband Project (1990). Analyses of radar and aircraft data collected in convective cells embedded in H awaiian rainbands are included for model validation. A Cloud Condensat ion Nuclei (CCN) activation spectrum, a condensational growth equation including the CCN chemical composition, collection efficiencies, and terminal velocities of the growing drops, are all provided. A sample s et of figures from the test run with bulk microphysical parameterizati on illustrates the desired format for comparisons between the detailed model results and for validation of the model output with observation s. This simple yet realistic test formulation includes vertical and ho rizontal advection, and can be used to evaluate microphysical model pe rformance without complexities resulting from dynamical-microphysical interactions in dynamic cloud models. Without such interactions, scien tists can focus on key physical processes involved in the formation of warm rain. The accurate representation of these processes in detailed models is essential to successfully simulate the observed evolution o f warm precipitating clouds. (C) 1998 Elsevier Science B.V.