Future changes of cluster high temperature events over China from RegCM4 ensemble under RCP4.5 scenario

Abstract Using the daily maximum temperature of the RegCM4 dynamical downscaling from four global climate models under the historical and RCP4.5 simulations, this study firstly identified the cluster high temperature event (CHTE) occurring in China through a simplified objective method, and then projected its change during the 21st century in terms of the CHTE metrics including frequency, duration, extreme intensity, cumulative intensity, maximum influential area, average influential area, and comprehensive intensity. The ensemble projection indicates that all the CHTE metrics tend to increase toward the end of the 21st century on the national scale. Besides, the occurrence of CHTE shows a longer month span during the middle and the end of the 21st century (from April to October) compared to the present (from April to September), accompanied with the peaks of the frequency, duration, and cumulative intensity shifting from the present July ahead to June. Relative to 1986‒2005, the projected slight, moderate, and extreme CHTEs increase by 55%, 50%, and 50% (58%, 43%, and 60%) during 2046‒2065 (2080‒2099), respectively; the projected severe CHTE increases by 11% during 2046‒2065 while decreases by 11% during 2080‒2099. Spatially, the CHTE frequency, duration, and cumulative intensity are projected to increase in a widespread region. The largest increase appears in southern China for the frequency and in Xinjiang and Southeast China for the duration and cumulative intensity. We further divided China into five sub-regions to examine the regional features of CHTE changes. It is found that in addition to the increase of CHTEs in each single sub-region, a pronounced enhancement is also projected for the occurrence of cross-regional CHTEs, particularly for that across more than two sub-regions.