Radar Observations of Tropical Weather Systems

Abstract

Radars have been instrumental in tropical meteorology studies dealing with the structure and organization of convective weather systems. Deep convection in the tropics is a primary mechanism for transporting heat from the planetary boundary-layer to the upper troposphere (Riehl and Malkus, 1958). Clouds in the tropics occur in a spectrum of sizes ranging from isolated cumulus to mesoscale convective systems (MCSs), where MCS is defined as in Zipser (1982). Early satellite studies indicated that deep convection was concentrated in the relatively long-lived (∼24 h) MCSs, referred to as “cloud clusters” (Martin and Karst, 1969; Frank, 1970; Martin and Suomi, 1972), identified by their extensive (100–1000 km wide) cirrus canopies. Because of their large size and duration, MCSs accomplish much of the vertical heat transports required by the large scales. Reed and Recker (1971) showed that the frequency of tropical MCSs is in turn modulated by synoptic-scale wave disturbances, indicating that MCSs are intricately tied to other scales of motion in the tropics. Furthermore, some MCSs evolve into tropical cyclones, which affect large regions of the tropics and midlatitudes.