METHODS OF SHORT-TERM FORECASTING OF NONCONVECTIVE CLOUDS AND PRECIPITATION USING A MOISTURE TRANSFORMATION MODEL, WITH MICROPHYSICS PARAMETRIZATION. 2. A CLOUD FORECASTING METHOD BASED ON THE COMPUTED LIQUID WATER CONTENT FIELD AND NONCONVECTIVE CLOUD MICROPHYSICS PARAMETRIZATION

L. R. Dmitrieva-Arrago

On the basis of the results of the moisture transformation model as described in the first part of the paper [3], a method is proposed for microphysics param¬etrization of droplet and mixed clouds. The liquid water content space distribution and physical hypotheses are used. For the particle size spectrum, the gamma distribution is accepted. One of the parameters is constant, and the second varies at every time step due to coagulation and to the Bergeron—Findeisen process. The cloud phase composition is determined as dependent on temperature. A method for precipitation computation using a microphysical algorithm is developed. A technique is presented for computing critical water content, which regulates the precipitation amount, and the dependence of the critical water content on the portion of crystals and on microphysical parameters of the clouds is studied. The influence of the water content initial data on the results of precipitation computation is analyzed. Estimates of the precipitation forecast efficiency are presented. Peirce's index for the precipitation occurrence/nonoccurrence forecasts is within 0.3-0.53.