A double moment warm rain scheme: description and test within a kinematic framework

A two-moment warm rain parameterization that includes prognostic equations for mixing ratios and number concentrations is described. The number of activated condensation nuclei is also prognosed assuming a log–linear relationship between the total number of activated condensation nuclei and the supersaturation. Collective processes are evaluated using pre-calculated matrices of interaction based on numerical integrations of the corresponding stochastic collection equations. Mass transfer between cloud and raindrops due to autoconversion is evaluated using Berryʹs parameterization, its attendant raindrop number concentration change is calculated considering the corresponding rates of change for the first and second moments of the raindrop volume distribution. A Doppler kinematic reconstruction of a summertime Hawaiian rainband occurred on August 10, 1990 is used to evaluate the credibility of this scheme.