Intensification of extreme precipitation in arid Central Asia

Changes in total and extreme precipitation are expected to intensify under climate warming. As Central Asia is among the driest regions in the world, more information is needed regarding the past and potential future changes in extreme precipitation in this region. In this study, we investigated changes in total and extreme precipitation in Central Asia based on observational records and Coupled Model Intercomparison Project 5 (CMIP5) model simulations. The results showed that all extreme precipitation-related indices except for consecutive dry days (CDD) experienced an increasing trend during 1936-2005. The annual total wet-day precipitation (PRCPTOT), daily intensity index (SDII), annual maximum 1- or 5-day precipitation amount (Rx1day and Rx5day), total annual number of days with precipitation exceeding heavy precipitation or very heavy precipitation thresholds (R10 and R20), and CDD were statistically robust. Generally, the statistically significant increasing trends are more pronounced in the wetter sub-regions, i.e. Northern and Southeastern Central Asia. Based on the CMIP5 model simulations, the PRCPTOT, Rx1day, and CDD in Central Asia are projected to increase robustly during 2006-2100 under representative concentration pathway (RCP) 4.5 and RCP 8.5; higher RCPs had higher rates of extreme precipitation and lower signal-to-noise ratios (SNRs). In addition, a considerable intensification of extreme precipitation and slight drought is predicted for the late 21st century (2071-2100). In Central Asia, the PRCPTOT, Rx1day, and CDD had an approximately linear relationship with global warming rates, with rates of 4.95%/K, 5.79%/K, and 2.79%/K, respectively, under RCP 4.5. The response rates were slightly lower under RCP 8.5 than under RCP 4.5 for these indices. The increase in total precipitation was mainly due to the intensification of extreme precipitation and a concomitant weakening of light precipitation, with a simultaneous overcompensation of increased evaporation due to global warming. Thus, our results suggest that total and extreme precipitation will intensify in Central Asia under a warming climate. Since increased extreme precipitation may lead to a heightened risk of flooding, water availability is predicted to remain limited over Central Asia.