RELATIONSHIPS BETWEEN TROPICAL PRECIPITATION AND KINEMATIC CLOUD MODELS.
Abstract
The results of the latest two experiments in the numerical simulation of moist convection are presented. Experiment 1 effectively suppresses the precipitation process. Experiment 2 simulates a precipitating roll cloud with variable precipitation fall velocity. The lower portion of the cloud is progressively dissipated in both experiments; more rapidly so in Experiment 2. The primary cause of the dissipation is evaporation of subsiding cloud in the indirect circulation cell which develops below the buoyant bubble. However, the accretion of cloud droplets by falling precipitation in Experiment 2 results in a more efficient dissipation of the lower cloud. Furthermore, in Experiment 2, a secondary buoyant bubble develops beneath the cloud base. It is shown that this development occurs because the evaporation of precipitation in the nearly saturated air below the cloud is insufficient to offset the compressional heating of the descending air in the sub-cloud layer. To obtain further insight into the developments in the two experiments, the buoyancy forces are examined. It is seen that the bubble becomes more buoyant in Experiment 2 because the liquid water in precipitation, the major source of negative buoyancy, is continuously being removed. The equations required to evaluate the energy and water substance budgets are derived from the model equations. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1967
- Accession Number
- AD0825820
Entities
People
- G. Arnason
- R. S. Greenfield