A Determination of the Trade-Wind Cumuli Population Using BOMEX Data and an Axisymmetric Cloud Model.

Abstract A cumulus cloud population is determined over the trade-wind region under an undisturbed weather condition from the large-scale heat and moisture budgets. The BOMEX data during the period 22–23 June 1969 are used. Six classes of clouds (A–F) are considered. Each class of clouds changes the large-scale mean temperature and humidity through condensation, evaporation and convective transport processes. The change due to each class of clouds is determined using the time-dependent, two-dimensional, axisymmetric cloud model developed by Soong and Ogura (1973). It is found that the cloud population, consisting of 66.4 A clouds, 8.9 D clouds and 1.6 E clouds km−2 DAY−1, satisfies approximately the large-scale heat and moisture budget requirements. The cloud top heights of the three classes of clouds are 0.8, 1.6 and 2.0 km, respectively, and the cloud radii at the cloud base level during the mature stage are 62.5, 150 and 225 m, respectively. Consequently, the fractional area coverage of the predicted cl...