Projected change in East Asian summer monsoon by dynamic downscaling: Moisture budget analysis

Abstract

The summer monsoon considerably affects water resource and natural hazardsincluding flood and drought in East Asia, one of the worlds most densely populatedarea. In this study, we investigate future changes in summer precipitation over EastAsia induced by global warming through dynamical downscaling with the WeatherResearch and Forecast model. We have selected a global model from the CoupledModel Intercomparison Project Phase 5 based on an objective evaluation for EastAsian summer monsoon and applied its climate change under RepresentativeConcentration Pathway 4.5 scenario to a pseudo global warming method. Unlike theprevious studies that focused on a qualitative description of projected precipitationchanges over East Asia, this study tried to identify the physical causes of theprecipitation changes by analyzing a local moisture budget. Projected changes in precipitation over the eastern foothills area of Tibetan Plateau including Sichuan Basin and Yangtze River displayed a contrasting pattern: a decrease in its northern area and an increase in its southern area. A local moisture budget analysis indicated the precipitation increase over the southern area can be mainly attributed to an increase in horizontal wind convergence and surface evaporation. On the other hand, the precipitation decrease over the northern area can be largely explained by horizontal advection of dry air from the northern cor EastAsia induced by global warming through dynamical downscaling with the WeatherResearch and Forecast model. We have selected a global model from the CoupledModel Intercomparison Project Phase 5 based on an objective evaluation for EastAsian summer monsoon and applied its climate change under RepresentativeConcentration Pathway 4.5 scenario to a pseudo global warming method. Unlike theprevious studies that focused on a qualitative description of projected precipitationchanges over East Asia, this study tried to identify the physical causes of theprecipitation changes by analyzing a local moisture budget. Projected changes in precipitation over the eastern foothills area of Tibetan Plateau including Sichuan Basin and Yangtze River displayed a contrasting pattern: a decrease in its northern area and an increase in its southern area. A local moisture budget analysis indicated the precipitation increase over the southern area can be mainly attributed to an increase in horizontal wind convergence and surface evaporation. On the other hand, the precipitation decrease over the northern area can be largely explained by horizontal advection of dry air from the northern co