Projected Summer Climate Changes over South Asia Based on the Nested FGOALS/RegCM Model

This paper presents a dynamical downscaling simulation of future summer climate over the CORDEX (COordinated Regional climate Downscaling EXperiment) South Asia domain using the regional climate model RegCM3 nested within FGOALS-g2 (Grid-point version 2 of Flexible Global Ocean-Atmospheric-Land System Model). The projection under the RCP8.5 scenario in the near term (2016-2035) and long term (2080-2099) shows that the spatial pattern of the climate change in the near term is similar to that in the long term, but the variation amplitude in the long term is greater. The main features are listed as follows: The strength of the low-level jet (LLJ) will be weakened and the position will shift northward. The average precipitation over South Asia will decrease, but precipitation over the northern part will increase. The spatial distribution of precipitation change over land is mainly controlled by precipitation frequency, and changes in the distribution of mean precipitation frequency show remarkable geographic differences. The precipitation change is directly related to the moisture transport change. In RegCM3, changes in moisture transport are mainly controlled by the weakening and northward shifting of the LLJ, and the weakening of the LLJ cannot be offset by the increase in precipitable water. Meanwhile, in FGOALS-g2, precipitation will increase as the increase in precipitable water can offset the weakening of the LLJ.