Changes in concurrent precipitation and temperature extremes over the Asian monsoon region: observation and projection

Concurrent precipitation and temperature extremes exert amplified impacts on the ecosystems and human society; however, they have not been well documented over the Asian monsoon region with dense population and agricultures. In this study, the spatiotemporal variations of four concurrent extreme modes (cold/dry, cold/wet, warm/dry, and warm/wet) are detected based on observations and model projections. From 1961 to 2014, the 'dry' modes manifest large values at high latitudes, while the 'wet' modes occur frequently in tropical regions. Based on the linear congruency, the trends of the four modes are largely determined by extreme temperature. Furthermore, the interaction between extreme precipitation and extreme temperature (IEPET) facilitates the trends of the dry modes, and inhibits the trends of the wet modes. Three modeling datasets (CMIP6, NEX-GDDP-CMIP6, and BCSD_CMIP6) are employed to project future changes in the occurrences of four concurrent modes. The BCSD_CMIP6, generated by statistical downscaling of the CMIP6 simulations, stands out in simulating the observed features of extreme precipitation and extreme temperature over the Asian monsoon region. Extreme temperature is also identified as the main driver in the future trends of the four modes, while the IEPET is not conducive to the decreasing trend of the cold/dry mode, implying that the IEPET would change under global warming. The warm/wet mode manifests the largest change among the four compound extremes from 1995 to 2014 and two projected periods (2046-2065 and 2080-2099) relative to 1961-1980. On the annual timescale, the change magnitudes over Southeast Asia, South Asia, the Tibetan Plateau, and Eastern Central Asia are relatively larger than in the other sub-regions during historical and future periods, which are quantified as the hotspots of the warm/wet mode. On the seasonal timescale, the future hotspots will change relative to the historical period. Our findings are critical for formulating adaptation strategies to cope with the adverse effects of compound extremes.