Relationship between Indian monsoon precipitation and air temperature over the Tibetan Plateau

The Asian monsoon is generally believed to be resulted from the differential heating between Eurasian land mass and adjacent oceans and influenced by the heating of the Tibetan plateau during the course of development and variation of the monsoon. In this study, we examine the statistical relationship between monthly precipitations averaged for all India and 7 Indian regions and air temperatures at 8 levels over the Tibetan plateau (25-45°N, 75-105°E) for 1949-1996. The result shows that the June-September (JJAS) monsoon precipitation exhibits a significant positive correlation with the plateau air temperature at levels from 200hPa to 600hPa in early autumn. The correlation coefficient between the JJAS precipitation and the 250hPa temperature in September reaches 0.51 for 48 years. That suggests that the monsoon precipitation anomaly could lead rather than lag the plateau temperature variation, which means that the summer-autumn temperature variation in the middle and upper troposphere over the Tibetan plateau could be the result rather than the cause of the monsoon anomaly. However, there is a high correlation between 200hPa temperature over the plateau in spring (March-May) and succeeding June Indian precipitation, which indicates that the monsoon precipitation anomaly is related to the heating of the plateau before the starting of the summer monsoon to a certain degree, although the air temperature over the plateau could be mainly controlled by diabatic heating induced by the monsoon precipitation after the monsoon begins. It is also noted that the correlation between November Indian precipitation and October plateau temperature is negative and strong. Possible dynamic causes leading to the observed correlation relationship are discussed preliminarily. This result suggests that the relationship between the monsoon precipitation and the plateau temperature is complex and interactive. Thus, author proposes that possible links between the tropospheric temperature, monsoon precipitation and atmospheric heating should be explored further.