Mesoscale convective complexes in the western Pacific region

Abstract

A climatological study of mesoscale convective complexes (MCCs) during 1983-1985 over the western Pacific region (WPR), using full-disc, enhanced infrared satellite imagery from the Japanese Geostationary Meteorological Satellite is presented. The systems are nocturnal and tend to form over or in the immediate vicinity of land. Cold-cloud shields in the Americas last for about 10h while WPR shields last about 11h. The cold-cloud-shield size distribution is similar to that of the Americas, with most systems exhibiting areas between 2×105 and 3×105km2. The frequency of midlatitude systems peaks in late spring and early summer while low-latitude MCCs are distributed uniformly throughout the warm season. Climatologically, low-level jets of high-θe air and upper-level diffluence are present in these zones. Tracks of WPR MCCs show that, like American systems, they typically move to the right (left in the Southern Hemisphere) of the climatological mean 700-500mb flow. The deviation from the mean flow is in the direction of the source region of highest-θe air. A few MCCs that moved over water formed tropical storms. Likewise, a few tropical systems moved over land and formed MCCs. -from Authors