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 act ivated condensation nuclei is also prognosed assuming a log-linear relation ship between the total number of activated condensation nuclei and the supe rsaturation. Collective processes are evaluated using pre-calculated matric es of interaction based on numerical integrations of the corresponding stoc hastic collection equations. Mass transfer between cloud and raindrops due to autoconversion is evaluated using Berry's parameterization, its attendan t raindrop number concentration change is calculated considering the corres ponding rates of change for the first and second moments of the raindrop vo lume distribution. A Doppler kinematic reconstruction of a summertime Hawai ian rainband occurred on August 10, 1990 is used to evaluate the credibilit y of this scheme. (C) 1999 Elsevier Science B.V. All rights reserved.