Radar Characteristics of Tropical Convection Observed During GATE: Mean Properties and Trends Over the Summer Season

Abstract

Radar echo patterns observed daily during GATE have been analyzed to determine their mean characteristics and variations over the summer season. The characteristics analyzed were average echo areas, maximum heights, durations, number of high-intensity cores, motions, formation and dissipation modes, and orientations of echo lines. As in tropical convective echo patterns in other parts of the world, small echoes (< 102 km2 area) dominated the total number of echoes while large echoes (> 103 km2 area) accounted for most of the area covered by precipitation. Echo height, duration and number of embedded cores were all positively correlated with echo area, and the most intense echo cores were found in the largest echoes, indicating that echo regions > 104 km2 in area were the areas of most enhanced convection. Echo areas, heights and durations tended to be log-normally distributed. During late summer, the convection in large echoes (> 104 km2 area) was enhanced, showing greater vertical development as well as more numerous and more intense embedded cores than earlier in the summer. Lower tropospheric winds appeared to control echo motions and played a role in the horizontal alignment of echo lines.