Future Precipitation Extremes in China under Climate Change and Their Physical Quantification Based on a Regional Climate Model and CMIP5 Model Simulations

Abstract

The atmospheric water holding capacity will increase with temperature according to Clausius-Clapeyron scaling and affects precipitation. The rates of change in future precipitation extremes are quantified with changes in surface air temperature. Precipitation extremes in China are determined for the 21st century in six simulations using a regional climate model, RegCM4, and 17 global climate models that participated in CMIP5. First, we assess the performance of the CMIP5 models and RCM runs in their simulation of extreme precipitation for the current period (RF: 1982–2001). The CMIP5 models and RCM results can capture the spatial variations of precipitation extremes, as well as those based on observations: OBS and XPP. Precipitation extremes over four subregions in China are predicted to increase in the mid-future (MF: 2039–58) and far-future (FF: 2079–98) relative to those for the RF period based on both the CMIP5 ensemble mean and RCM ensemble mean. The secular trends in the extremes of the CMIP5 models are predicted to increase from 2008 to 2058, and the RCM results show higher interannual variability relative to that of the CMIP5 models. Then, we quantify the increasing rates of change in precipitation extremes in the MF and FF periods in the subregions of China with the changes in surface air temperature. Finally, based on the water vapor equation, changes in precipitation extremes in China for the MF and FF periods are found to correlate positively with changes in the atmospheric vertical wind multiplied by changes in surface specific humidity (significant at the p < 0.1 level).

摘 要

气温升高增强大气的持水能力,进而影响降水,特别是极端降水发生。本文利用区域气候模式RegCM4的6套模拟结果及17个参与CMIP5的模式结果,研究了中国21世纪极端降水变化。首先,我们评估了RegCM4及采用的17个CMIP5模式对中国历史时期(RF: 1982-2001)极端降水的模拟能力。跟观测相比,RegCM4和CMIP5模式都能合理模拟极端降水的空间格局。RegCM4模拟结果及CMIP5多模式集合结果得到的中国四个子区域上极端降水在21时期中叶(MF: 2039–58)及末期(FF: 2079–98)均高于历史时期,CMIP5模式模拟的中国极端降水从2008年到2058年呈增长趋势。相对于CMIP5模式结果,RegCM4模拟的极端降水有更高年际变率。其次,我们研究了气候变化下21世纪中叶及末期极端降水的变率,如21世纪中叶,华南地区气温每升高1oC,极端降水事件R95p相对于历史时期增加3.45%。最后,基于水汽方程,我们发现21中叶及末期的中国极端降水变化与大气垂直风速变化和地面比湿变化的乘积呈正相关关系。