Due to weakening of the Asian summer monsoon, the major
monsoonal rain belt has experienced an inter-decadal southward shift,
thus leading to the anomalous precipitation pattern of droughts in
north and floods in south. The inter-decadal variability of the
land-sea thermal contrast between heat sources affected by the winter
and spring snow over the Tibetan Plateau and SSTA variations in
surrounding oceans is the dominating factor leading to weakening of the
Asian summer monsoon. In recent 10-15years, the enhancement of land-sea
thermal contrast has caused the northward advance of the monsoon rain
belt from the Yangtze River basin to the Yellow- Huaihe river basins.
This is related to a similar northward shift of positive correlation
region between the winter and spring snow over TP and summer
precipitation in East China.
Under the forcing of greenhouse gases with inclusion of sulfate aerosols, the monsoon in India and some regions of China would weaken and related precipitation would decrease by 10%.The main reason involves with decreasing land-sea thermal contrast due to cooling effect of hazy clouds and decrease in water vapor content. In the future, the East Asian summer monsoon will continue to enhance and the precipitation amount in North China will significantly increase, whereas the South Asian monsoon will continue to weaken, with precipitation patterns to change considerably.