The Effect of Utilizing Empirically Derived Values of Coalescence Efficiency in a Microphysical Cloud Model
Abstract
A one-dimensional eulerian warm cloud model which incorporates the effects of stochastic coalescence, drop breakup, and vertical water mass transfer is used to determine the effect of empirically derived values of the coalescence efficiency. A constant vertical updraft profile is utilized to artificially produce liquid water increases and to produce a realistic restraint for hydrometeor fallout. Although coalescence efficiency to be equal to one, the recent work of Whelpdale and List, and Levin et al., indicate that coalescence efficiency is closely related to droplet/drop size ration P, and decreases with increasing P. Starting with an initial droplet spectrum for a tropical cumulus which produces rain within 20 minutes when using a coalescence efficiency of one, comparative runs are made using the empirical data. Utilization of these efficiencies leads to delay of precipitation and to decreases both in rainfall intensity and cumulative rainfall. Using the more restrictive of the two sets of efficiency data considered forces liquid water contents to be unreasonably large in order to sufficiently stimulate the coalescence mechanism.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1974
- Accession Number
- AD1223043
Entities
People
- Paul M. Tag