WMOD00590

• Title: Analysis and Classification of Mesoscale Cloud and Precipitation Systems
• Date: 8/1/1983
• Weather Modification - Doc Type: Report

(1977). Tropical clusters have been more recently studied by Gray
(1973), Williams and Gray (1973) and Ruprecht and Gray (1976).
Special tropical convective experiments such as VIMHEX, BOMEX and
GATE have gathered data to understand the evaluation of mesoscale
convective systems. Much detailed understanding of the physical
processes that initiate and maintain tropical mesoscale convective
systems has been gained from researchers who studied these data sets
(e.g., Zipser, 1969; Riehl, 1978; Frank, 1977; Zipser and Gautier,
1978; Leary and Houze, 1979, 1980; Johnson. 1980; Soong and Tao,
1980). Current results from studies by Gamache and Houze (1982) and
Zipser (1979) clearly show the importance of mesoscale lifting in the
initiation and maintenance of tropical convective precipitation
systems.

Convective clouds in the subtropics have been studied in the
FACE weather modification experiment (e.g., Simpson and Woodley,
1971, 1975; Woodley et ale (1982). Convective cloud mergers, first
documented in Florida by Byers and Braham (1949), were studied
extensively by Ulanski and Garstang (1978a, b) who found surface
convergence fields and moisture flux as a pre-condition for penetra-
tive precipitating convection. Convergence zones of 2 to 50 km2
were found to precede convective showers, and the magnitude and
duration of convergence was an excellent predictor of rainfall amount
during two seasons. Ulanski and Garstang (1978b) proposed a physical
model of convective initiation based on observations. Simpson et ale
(1980) described the physical characteristics of cumulus mergers and
noted their importance in producing one or two orders of magnitude
more precipitation than that from isolated showers. The gust front
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