Intensified East Asian summer monsoon and associated precipitation mode shift under the 1.5 °C global warming target

摘要

In this study, the East Asian summer climate changes under the 1.5 °C global warming (1.5 GW) target in 30 simulations derived from 15 coupled models within the Coupled Model Intercomparison Program phase 5 (CMIP5) are examined. Compared with the current summer climate (1975-2005), both surface air temperature and precipitation increase significantly over the East Asian continent during the 1.5 GW period (average period 2021-2051). In northeastern China this is particularly pronounced with regional averaged precipitation increases of more than 7.2%, which is greater than that for the whole East Asian continent (approximately 4.2%). Due to stronger enhancement of precipitation north of 40°N, the leading empirical orthogonal function (EOF) mode of summer precipitation over the East Asian continent changes from tripolar-like mode to dipole mode. As there is stronger surface warming over the East Asian continent than that over surrounding ocean, the land-sea thermal contrast is enhanced during the 1.5 GW period. As a result, the monsoon circulation in the lower troposphere is significantly strengthened, which causes the increased summer precipitation over the East Asian continent. In addition, larger interannual variabilities of East Asian summer monsoon circulation and associated precipitation are also suggested for the 1.5 GW period.