华东地区极端降水动力降尺度模拟及未来预估

Dynamical Downscaling Simulation and Projection of Extreme Precipitation over East China

利用CMIP5(Coupled Model Intercomparison Project Phase 5)数据集中的全球模式IPSL-CM5A-LR及其嵌套的区域气候模式WRF (Weather Research and Forecasting),分别评估了模式对1981～2000中国华东区域极端降水指标的模拟能力,并讨论了RCP8.5排放情景下21世纪中期(2041～2060年)中国华东极端降水指标的变化特征。相比驱动场全球气候模式,WRF模式更好地再现了各个极端指数空间分布及各子区域降水年周期变化。在模拟区域气候特点方面,WRF模拟结果有所改进,并在弥补全球模式对小雨日过多模拟的缺陷起到了明显的作用。21世纪中期,华东区域的降水将呈现明显的极端化趋势。WRF模拟结果显示年总降雨量、年大雨日数、平均日降雨强度在华东大部分区域的增幅在20%以上;年极端降雨天数、连续5 d最大降水量的增幅在华东北部部分区域分别超过了50%和35%,同时最长续干旱日在华东区域全面增加;且变化显著的格点主要位于增加幅度较大的区域。未来华东区域会出现强降水事件和干旱事件同时增加的情况,降水呈现明显的极端化趋势,且华东北部极端化强于华东南部。

Based on the Weather Research and Forecasting(WRF)model driven by the global model IPSL-CM5A-LR results that are included in the model output archive of the Coupled Model Intercomparison Project Phase 5,this study has assessed the model ability for simulating extreme precipitation indices and analyzed possible future changes in the mid-21st century(2041-2060)under the RCP8.5 scenario over East China.Results indicate that WRF performs well in the simulation of extreme precipitation indices.Compared with IPSL-CM5A-LR model,WRF model can better reproduce the spatial distribution and annual cycle of precipitation over East China and the sub-regions.In particular,the simulation of regional features is improved in WRF and the problem in global model to overestimate light precipitation has been overcome.Prediction results show that East China will experience an obvious trend of extremeness on precipitation.WRF simulation results show that indices of annual total wet-day precipitation(PRCPTOT),number of heavy precipitation days(R10mm),and simple daily intensity index(SDII)indices in most regions of East China will increase by more than 20%,the increases of extreme wet days(R95d)and max 5-d precipitation(Rx5day)indices in the northern part of East China will be more than 50%and 35%,and consecutive dry days(CDD)overall will increased in East China.Model grids with significant changes are mainly located in areas with large increases.There will be an extremalization in precipitation with increases in both strong precipitation and drought events,and the degree of extremalization is stronger in the north than in the south of East China.