Venezuelan Rainstorms as Seen by Radar

Abstract

The underlying premise of the research is that a contribution can be made to understanding the interrelation between mesoscale cumulonimbus systems and synoptic disturbances as well as the general circulation by following individual cloud histories in detail. During a mesoscale experiment carried out in eastern Venezuela in 1969, 232 such histories were obtained. At first the statistical properties of the sample are explored with respect to maximum height attained by clouds; maximum area; duration of cumulonimbus systems and radar index; correlations between maximum height, maximum area and duration; symmetry of time histories; vertical motion of echoes; diurnal effects; echo displacement in relation to tropospheric winds; and merger or separation of echoes. In the second part it is shown that the observed outflow profiles of mass in the upper troposphere from synoptic disturbances or poleward from the tropics as a whole can be parameterized largely by erosion of the buoyant energy of cumulonimbus towers through entrainment of mid-tropospheric air at the fractional rate of 0.6 for the layer 850?400 mb.