WEAKENING OF INDIAN SUMMER MONSOON AND ITS RELATION WITH TROPOSPHERIC TEMPERATURE VARIATION

The analysis of 43-year NCEP NCAR reanalysis data and the station observations reveals the correlation between troposphere temperature variations and the weakening of the Indian summer monsoon circulation. The Indian summer monsoon variation is strongly linked to tropospheric temperature over East Asia, showing significant positive correlations of mean tropospheric temperature with all-Indian summer rainfall and the monsoon circulation intensity. The result shows Indian summer monsoon circulation underwent twice weakening processes for recent decades. The first occurred in the circ. mid-1960s, and the other occurred in the circ. late 1970s. The finding indicates that the mean tropospheric temperature may play a crucial role in weakening of the Indian summer monsoon intensity via changing land-sea thermal contrast. The troposphere temperature contrast between East Asia and the tropical area from the eastern Indian Ocean to the tropical western Pacific lead to weaken the Indian summer monsoon circulation.