Analysis on Characteristics of Interannual Variability of the South Asian Summer Monsoon

Characteristics of interannual variability of the South Asian summer monsoon are analyzed by using the NCEP\|NCAR monthly mean reanalysis data from 1958 to 1997. The Results show that the zonal wind shear between 850 and 200 hPa represents the main characteristic of the South Asian summer monsoon activity, the summer monsoon duration is from June to September and the key region is in 0°~ 20°N, 40°E ~130°E. The analyses based on these show that unitary variation of the South Asian summer monsoon in the region is primary. The opposite variation of the west part from the east part, in which the line of demarcation appears about the 80°E, is secondary and represents chiefly variation of the Southeast Asian summer monsoon in the east. Following above all, four main types are categorized. For the different types, precipitation rate patterns are obviously different.