资源环境科技发展态势分析平台

Projections for South Asian summer monsoon (SASM) precipitation under three representative concentration pathways (RCPs, including RCP2.6, RCP4.5 and RCP8.5) were investigated using 12 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Most models returned results indicating intensified monsoon precipitation over the Asia-Pacific region. The main discrepancies among the models occurred in the vicinities of Iran and Eastern China. Moreover, all projections indicated that the onset of SASM precipitation would be delayed over latitudes spanning 10 degrees-20 degrees N and advanced over latitudes north of 20 degrees N in the 21st near the end of the 21st century. Some of the factors potentially impacting SASM precipitation were also considered. Intensified SASM precipitation can be directly attributed to intensified water vapour flux resulting from positive westerly anomalies, especially over the Arabian Sea. By investigating the water vapour flux, its thermodynamic response to the external forcing should be the main cause of intensified SASM precipitation. The change of atmospheric circulation can be further linked to an enhanced land-sea temperature contrast over the Asian-Australian monsoon region, as well as decreased snowfall during the cold season over the Eurasian continent. Multi-model results indicated that the negative correlation between projected SASM precipitation and El Nino will show little inter-annual change during the 21st century.