Numerical Simulation Of Warm Rain Process

Abstract

Extensive aircraft cloud physical observations made in more than 2000 tropical cumulus clouds indicated new observational evidence viz., (1) horizontal structure of the air flow inside the cloud has consistent variations with successive positive and negative values of vertical velocity representative of ascending and descending currents, (2) regions of ascending currents are associated with higher liquid water content (LWC) and negative cloud drop charges and the descending currents are associated with lower LWC and positive cloud drop charge, (3) width of the ascending and descending currents is about 100 m, (4) ratio of the measured LWC (q) to that of the adiabatic value (qa) = 0.60 at cloud-base levels, (5) increase in the cloud electrical activity with LWC, (6) cloud drop size spectra is unimodal near the cloud-base and multimodal at higher levels, (7) in-cloud temperatures are colder than the environment, (8) environmental lapse rates are equal to the saturated adiabatic value while inside the cloud they are lower, (9) positive increments in the LWC are associated with the increments in temperature inside the cloud and the immediate environment and (10) variances of in-cloud temperature and humidity are larger in the regions where the values of the LWC are higher. The observed dynamical and physical characteristics of clouds cannot be explained by the presently available cloud models. An alternative cell dynamical system cloud model which predicts the observed cloud characteristics is discussed in this paper.