对CMIP5模拟北半球纬度带平均降水量的订正研究

Study on the correction of the average precipitation in the latitude belt of northern hemisphere simulated by CMIP5 climate

基于气候漂移和多重线性回归的订正方法,对第5次国际耦合模式比较计划26个模式的历史时期(1956-2005年)北半球月平均降水进行了订正,对未来(2006-2060年)的月平均降水进行了订正和预估.选取英国东英格利亚大学提供的CRU降水数据集作为评估模式订正效果的参考资料.结果表明,CMIP5模式结果的集合平均在青藏高原以南、格陵兰岛南部以及南海沿岸、南美洲北部的降水模拟值偏低,而高估了索马里、阿赞德高原、亚洲中部和北部、北美洲西部和北部.相较于观测结果,CMIP5模拟的低纬度纬向平均降水被整体低估,中、高纬度带上模拟值整体偏高.订正后,历史时期降水分布、纬向平均降水量的时间序列与CRU观测结果有较好的一致性.利用上述方法对未来RCP4.5排放情景下的预估场进行订正后,沿非洲的阿赞德高原、欧洲、东南亚北部和中国长江中下游、密西西比平原,未来55 a的年平均降水量比历史时期降水量减少30 mm左右;南美洲的赤道以北、印度半岛北部、阿拉伯半岛地区的未来平均降水量同比增加50 mm.北半球未来55 a的暖季,东西伯利亚西部、蒙古高原、墨西哥南部平均降水量比历史时期明显减少,格陵兰岛东北部地区的冷季降水同比增加.

Based on the correction methods including climate drift and multiple linear regression,monthly mean precipitation simulated by 26 models from the fifth international coupling model comparison program(CMIP5)over the northern hemisphere during historical period(1956-2005)was revised.The monthly mean precipitation in the future(2006-2060)was corrected and estimated.The climatic research unit(CRU)data set was selected as the reference to assess the revised result.The ensemble average result of 26 models from CMIP5 for historical periods showed that the CMIP5 models underestimates the precipitation over the southern Tibetan Plateau,northern Greenland,South China Sea coast and north south America,while overestimating the precipitation over Somalia,Azande Plateau,central and northern Asia,western and northern North America.Compared with the observation,the zonal mean precipitation simulated by CMIP5 was underestimated at low latitudes but overestimated at middle and high latitudes.After the revision,the spatial and temporal distribution and the time series of the zonal mean precipitation during historical periods were in good agreement with the observations from CRU.Based on revision for historical precipitation,the CMIP5 models predicted precipitation under the future representative concentration pathways scenario 4.5(RCP4.5)emission scenarios was also revised and estimated.The result indicated that the predicted annual mean precipitation in the next 55 a along the Azande Plateau,Europe,the north of Southeast Asia,the middle and lower reaches of the Yangtze River,and the Mississippi Plain would be about 30 mm less than that in the historical period,while it would increase about 50 mm over the north of the equator of South America,northern part of the Indian Peninsula,and the Arabian Peninsula.The annual mean precipitation would be significantly lower over the northern hemisphere’s warm season in the next 55 a than that during the historical period over the western Eastern Siberia,Mongolian Plateau and southern Mexico,while indicating a higher value in cold seasons over the northeast of Greenland.