末次盛冰期冰盖对全球季风活动的非对称性影响  

Asymmetric impact of last glacial maximum ice sheets on global monsoon activity

作　　者：曹剑[1] 吴立广[1] 

机构地区：[1]南京信息工程大学地球系统模拟中心,南京210044

出　　处：《气象科学》2016年第4期425-435,共11页Journal of the Meteorological Sciences

基　　金：国家自然科学基金资助项目(41275093)

摘　　要：将新研发的南京信息工程大学地球系统模式(NUIST Earth System Model version 1,NESM1)首次应用于古气候模拟中,在Paleoclmate Modelling Intercomparison Project Phase III(PMIP3)框架下设计了工业革命前(Pre-industrial,PI)、末次盛冰期(Last Glacial Maximum,LGM)和增加大陆冰盖(Ice sheets,IS)试验,验证了模式对工业革命前气候和LGM时期气候的模拟能力,并通过增加大陆冰盖试验分析了其对全球季风活动的非对称性影响。结果表明:与PI时期相比,LGM时期的温度和降水均有显著改变。其中,全球平均温度比PI时期降低了4.7℃,全球平均降水减少了0.3 mm·d^(-1),降水对温度变化的敏感性约2.3%·℃^(-1),这与其他耦合模式结果一致。末次盛冰期大陆冰盖对其气候变化有重要贡献,冰盖引起的地表反照率改变与地形抬升作用导致全球平均气温下降1.2℃,降水量减少0.06 mm·d^(-1)。进一步分析表明,末次盛冰期冰盖对全球气候的影响还具有显著南北半球差异,所导致的温度降低和降水减少主要集中在北半球,其中北半球的降温更是高达南半球的5倍;引起北半球季风区年平均降水减少0.24 mm·d^(-1),降水年较差减小0.34 mm·d^(-1),而南半球变化很小。这是由于北半球大幅降温导致的低层水汽含量减小,并与大陆冰盖引起的欧洲大陆和北美大陆反气旋环流共同作用而影响季风活动。在夏季,减少的低层水汽含量与减弱的季风环流使夏季降水显著减少;而在冬季,加强的季风环流能部分抵消水汽含量减小的作用,故冬季降水稍微减弱。此外,在欧洲大陆和北美大陆附近对流层低层反气旋环流作用下,导致亚欧和北美季风活动区域减小。The first attempt was made to simulate the paleoclimate by using the newly developed NUIST Earth System model version 1 （ NESM1 ）. Three experiments are designed in the framework of Paleoclimate Model Intereomparison Project Phase III （PMIP3） ： PreIndustry （PI）, Last Glacial Maximum （ LGM）, and Ice Sheets （IS） experiments to verify the model＇s capability. IS experiment is used to inves- tigate the asymmetric impact of LGM ice sheets on global monsoon activity. Results indicate that the NESM1 model is good enough to explain the cool and dry climate during the LGM period with a global cooling of 4. 7 ℃, a decreasing precipitation amount by 0. 3 mm. d-1 and the 2.3%· ℃ sensitivity ofprecipitation to surface air temperature（SAT） change, which is consistent with the previous studies. The LGM ice sheets play an important role in the formation of cool and dry LGM climate, which caused the global mean SAT to decrease by 1.2 ~C and global mean precipitation by 0. 06 mm-d-1. Further investi- gation demonstrates that the climate impacts＇ asymmetry of ice sheets are on Northern Hemisphere （NH） and Southern Hemisphere （SH）. The significant cooling is only shown in NH, which is 5 times as largeas in the SH. The mean monsoon precipitation and annual range are reduced by 0. 24 ram. d-1 and 0.34 mm· d-1, respectively, over the NH monsoon region, while the changes in SH monsoon region are not obvi- ous. There are two factors contributing to these changes, including the lower specific humidity caused by the decreasing air temperature and the changed large-scale circulation owing to the existence of ice sheets over the North Europe and North American. The dramatically decreasing summer monsoon rainfall is asso- ciated with the decreasing specific humidity and weakening summer monsoon circulation, while the mar- ginal change of winter monsoon precipitation is due to the cancellation effect between decreasing water va- por content and enhancing winter monsoon circulation. The anti-cyclonic c

关 键 词：NESM1 末次盛冰期 大陆冰盖 全球季风 

分 类 号：P467[天文地球—大气科学及气象学]