多模式产品对青藏高原极端气候模拟能力评估

Evaluation of ExtremeWeather Indices over Qinghai-Xizang Plateau in NEX-GDDP

NEX-GDDP数据具有分辨率高且其中所有模式分辨率统一的优点,其对青藏高原地区极端气候的模拟能力如何,鲜见报道。使用1986-2005年青藏高原地面气象台站逐日观测资料,选取了最能体现高原地区自然生态环境与社会经济活动受气候变化影响的10个极端气候指数:霜冻日数(FD)、结冰日数(ID)、最低气温极小值(TNn)、最高气温极大值(TXx)、暖日持续日数(WSDI)、冷日持续日数(CSDI)、年降水量(PRCPTOT)、连续无雨日数(CDD)、连续有雨日数(CWD)和日最大降水量(RX1day),从极端降水与极端温度两方面,全面评估了NEX-GDDP中21个模式对青藏高原极端气候的模拟能力。结果表明:(1)TNn和TXx的模式模拟结果平均值小于观测值,而其余8个极端气候指数的模式模拟平均值大于观测值。从变化趋势看,FD、ID、CSDI和CDD的观测值与模式模拟值变化趋势一致性强,其余6个极端气候指数的一致性较弱。(2)21个模式对所选极端气候指数的空间模拟能力和时序模拟能力差异较大,就相关系数而言,多模式产品的空间模拟能力好于时序模拟能力,就中心化均方根误差而言,时序模拟能力又优于空间模拟能力。(3)按照极端气候指数识别所用数据不同将其分为三类:日最低气温类极端气候指数(FD、TNn和CSDI)、日最高气温类极端气候指数(ID、TXx和WSDI)和日降水量类极端气候指数(PRCPTOT、CDD、CWD和RX1day)。基于21个模式对极端气候指数时序与空间模拟能力的评估,综合评选了三类极端气候指数的5个最优模式,各自依次分别为:①日最低气温类GFDLESM2G、GFDL-CM3、CCSM4、MIROC5和ACCESS1-0;②日最高气温类CanESM2、BNU-ESM、MIROC-ESM-CHEM、inmcm4、和CCSM4;③日降水量类BNU-ESM、CanESM2、CSIRO-Mk3-6-0、MIROC-ESM和MIROC-ESM-CHEM;在利用NEX-GDDP研究青藏高原未来极端气候事件变化时,建议将它们作为优选模式。

NEX-GDDP data has the advantages of high resolution and uniform resolution with all the models.However,there are few studies on evaluating the NEX-GDDP’s ability to simulate the extreme climate on the Qinghai-Xizang Plateau.Based on the daily observation dataset of meteorological stations for the period of 1986-2005 over the Qinghai-Xizang Plateau,this study selected ten extreme climate indices,i.e.,Frost days(FD),Ice days(ID),Min Tmin(TNn),Max Tmax(TXx),Warm spell duration indicator(WSDI),Cold spell duration indicator(CSDI),annual Total wet-day precipitation(PRCPTOT),Consecutive dry days(CDD),Consecutive wet days(CWD)and Max 1-day precipitation amount(Rx1day),which can directly reflect the influence of climate change on social and economic activities and geographical landforms in the plateau area,and comprehensively evaluated the abilities of 21 models that participate the NASA Earth Exchange/Global Daily Downscaled Projection(NEX-GDDP)in simulating extreme climate indices.The main conclusions are drawn as follows:(1)Except for the average values of TNn and TXx calculated by all models are lower than the average values calculated from observation dataset,the average values of other extreme climate indices calculated by all models are higher than the average values calculated by observation dataset.With respect to the variation trend of extreme climate indices,the FD,ID,CSDI and CDD trends calculated by observation shows strong consistency with those calculated by all models while weak consistency was seen for others extreme climate indices.(2)Large differences in spatial simulation ability can be seen among the 21 models,and in terms of correlation coefficient(r),the spatial simulation ability of all the models is better than that of time sequential simulation ability,while in terms of root mean square error(RMSE),the ability of sequential simulation ability is better than that of spatial simulation.(3)According to the data used to identify the extreme climate indices,the extreme climate indices is divided into three categories:daily minimum temperature category(FD,TNn and CSDI),daily maximum temperature category(ID,TXx and WSDI)and daily precipitation category(PRCPTOT,CDD,CWD and RX1day).Based on the 21 models’abilities to simulate the spatio-temporal variations of the extreme climate indices,five optimal modes for three extreme climate indices were selected as follows:①daily minimum temperature category:GFDL-ESM2G,GFDL-CM3,CCSM4,MIROC5 and ACCESS1-0.②daily maximum temperature category:CanESM2,BNU-ESM,MIROC-ESM-CHEM,inmcm4 and CCSM4.③daily precipitation category:BNU-ESM,CanESM2,CSIRO-Mk3-6-0,MIROC-ESM and MIROC-ESM-CHEM.Based on the above statements,the above optimal models are recommended when the NEX-GDDP is used to investigate the extreme climate change over the Qinghai-Xizang Plateau in the future.