The Monsoon Circulation and Cloudiness over the GATE Area

Abstract

Seven years of daily satellite observations, ten years of commercial aircraft observations, a space?altitude meteorological cross section during EQUALANT II, and data from other investigations including analyses of 50 years of ship observations by Florida State University are combined to determine the meteorological setting for the GARP Atlantic Tropical Experiment (GATE). The GATE lies in the western edge of the African monsoon. 1) A low-level monsoon trough lies across the GATE A?B scale ship array; 2) the trough is semianchored with little seasonal and interannual latitudinal variation in the monthly mean positions; 3) the trough is a strong gradient zone for most atmospheric parameters; 4) the major convective cloudiness is of the monsoon scale, zonally oriented, semianchored in the southern portion of the GATE area, and embedded in the westerly flow south of the trough line; and 5) the synoptic scale variability increases from June to September and is due mostly to vortices traveling vestward in the monsoon trough across the northern portion of the GATE area.