The Life Cycles of GATE Convective Systems

Abstract

The life cycles of GATE squall lines and loosely organized cloud clusters are analyzed and documented using radar and composited rawinsonde data. Time variations of the temperature, moisture, wind and vertical motion fields are presented for both types of systems. The convective systems are usually triggered by the approach of a middle-level trough in the easterlies. Low-level convergence increases prior to intensification of convection, possibly by several hours. Once the convection begins, the systems largely cause the changes in their upper and lower level divergence profiles through cumulus-induced and radiational heating. Squall line and cluster systems are found to be essentially similar except for their propagation speeds and their vertical wind shears.