Projection And Evaluation Of The Precipitation Extremes Indices Over China

Projection of the extreme climate events under the global warming is always ofgreat importance in the global change research field. In this paper, Climatology of theobserved annual extreme precipitation indices (SDH, CDD, R10, R5d, R95t) derivedfrom the daily precipitation at 550 stations in China during 1961-2000 are used toevaluate the simulation ability of 7 IPCC AR4 Coupled Climate Models, and theprojected change of the precipitation extreme indices over China under IPCC SRESA2,A1B and B1 are also studied. At the same time a variable-grid atmosphericgeneral circulation modle named LMDZ, whose boundary condition were taken fromthe outputs of the coupled climate modle IPSL,with a local zoom over theYangtze-Huaihe River Basin is used to investigate the potential changes in seasonalprecipitation extremes in the middle of the 21th century under the IPCC-A2 emissionscenario around the Yangtze-Huaihe River Basin;The statistical downscaling model(SDSM), a hybrid between a multilinear regression method and a stochastic weathergenerator,whose large-scale predictors were taken from the HadCm3 modle are alsoused to investigate the projected changes in seasonal precipitation extremes indicesover the Yangtze-Huaihe River Basin. The results show that:(1) The state-of-the-art IPCC AR4 models can simulate the spatial distributions ofprecipitation extremes well and the correlation coefficient between observedand simulated climatology field are 0.3-0.8, The multi-model ensemble (MME)show the best skill, But both the MME and single model failed to simulate theinter-annual variability and have large biases, such as there are excessiveextreme precipitation over the eastern side of the Tibetan Plateau while in themonsoonal regions the modeled intensity of precipitation extremes are lowerthan observed. (2) The projection results from the IPCC AR4 models show that in 21th century the precipitation will become more"extreme", there would be an overall increasing trend in extreme precipitation events over most of China such as the middle and lower reaches of the Yangtze River and the Tibetan Plateau under a wanning environment, and the change scope are scaled to the emissions scenarios.(3) Both of the dynamical downscaling modle LMDZ and the statistical downscaling modle SDSM showed better simulation skill than the nested AOGCMs IPSL and HadCM3, respectively, revealed that the downscaling can really "add value".Generally, winter showed the highest downscaling skill and summer the lowest. The LMDZ tended to simulate the intensity of extreme precipitation greater than observed and for SDSM the reverse. But both the LMDZ and the SDSM were "rain too frequent".(4) The result of the two downscaling model show that there would be less rain days and CWD will be shorter in the middle of the 21th century under the IPCC-A2 emission scenario around the Yangtze-Huaihe River Basin, but the intensity of extreme precipitation will increased, especially in Summer, when CDD and R5d will increase at the same time, indicated that the droughts and floods will become more frequent in this regions.