Dry/wet alternation and global monsoon

Abstract

This paper deals with dry/wet alternation and related globe‐scale monsoon. The data sets used are the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), the National Meteorological Center global wind analysis and the Upper‐Tropospheric Water Vapor (UTWV) band Brightness Temperature (BT) observed by NOAA polar orbiting satellites for 1980–1995. The BT and wind at 850hPa level are compared with the CMAP. Results show that the BT can indicate the convective precipitation in both tropical and subtropical regions. The summer monsoon in subtropics is defined as the expansions of three deep convective areas or three wet centers at the equatorial region. The major distributions of dry/wet alternation are determined according to the threshold of BT less than 244K. In the global mid‐low latitudes, there are six major seasonal dry/wet alternative regions with the dry/wet period lasting more than one month. The largest one is located over the subtropical North Africa‐Asia‐northwest Pacific. Other five alternative regions appear in the subtropical South Africa, Indonesia‐Australia, southwest Pacific, Mexico‐Caribbean Sea and subtropical South America. In Asia, the largest dry/wet alternative region covers all India, Indochina Peninsula, South China and southern Japan. These wet/dry alternative regions are the reflection of the seasonal advance of summer monsoon.