Abstract

A meteorological and hydrological experiment was carried out in the rainy season (June–September) of 1972 about 100 km south of Caracas, Venezuela. Of the total precipitation 50% fell in 10 h, i.e., in 0.5% of the total time. Nearly all stations in the 40–gage network had rain in each of the major rain events contributing 75% to the total precipitation. Rainfall was strongly controlled by the synoptic situation: The ratio of night to afternoon rain was 0.9, with afternoon showers normally making up the bulk of precipitation over the tropical land masses. The ratio of night plus morning rain to afternoon rain was 1.6; thermal and orographic controls were weak.

As consistently found in earlier studies, wet days were colder and moister than dry days. Because of the increased moisture, the equivalent potential temperature also was higher an the moist days. The cold and dense core is associated with a surface pressure rise of several millibars vanishing near 500 mb; the rain area thus is a relative high pressure center. The standard deviation of temperature at any level was greater on vet than on dry days, showing the effect of buoyant warm updrafts and cold downdrafts.

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