全球稳定增温1.5℃下北非夏季风降水的响应及其机理  

Response and mechanism analysis of North Africa summer monsoon precipitation under stabilized global warming of 1.5 ℃

作　　者：王雅君 曹剑[1] 江志红[1] WANG Yajun;CAO Jian;JIANG Zhihong(Key Laboratory of Meteorological Disaster of Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC),Nanjing University of Information Science and Technology,Nanjing 210044,China)

机构地区：[1]南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际联合研究实验室,江苏南京210044

出　　处：《大气科学学报》2023年第3期380-391,共12页Transactions of Atmospheric Sciences

基　　金：江苏省优秀青年基金资助项目(BK20220108);国家重点研发计划项目(2017YFA0603804);国家自然科学基金资助项目(42005017)。

摘　　要：利用第六次国际耦合模式比较计划(CMIP6)模式模拟结果,研究了21世纪末全球稳定增温1.5℃下北非夏季风降水的变化及机理。结果表明,全球稳定增温1.5℃较1985—2014年北非夏季风降水将增加0.26 mm/d,区域降水敏感度为4.8%/℃,且季风区北部降水增幅大于南部。基于水汽收支诊断发现热力项对季风区总降水增加作用明显,动力项对降水空间变化起重要作用。进一步分析当地水汽条件及相应环流场发现:在热力上,相对于1985—2014年,稳定增温1.5℃加强了北非地区表面温度及低层水汽输送,有利于当地维持更高的大气可降水量。在动力上,稳定增温1.5℃下显著的撒哈拉沙漠增温加大了海陆温度梯度,增强了对流层低层季风环流,同时非洲东风急流北移,使得季风区北部低层气流辐合加强,而高层热带东风急流减弱会导致季风区高层辐散运动减弱。总的来说,热力项增加了整个季风区降水,而动力项增强了季风区北部降水,减弱南部降水,主导了降水变化的空间格局。The response of North Africa(NA)summer monsoon precipitation to stabilized global warming of 1.5℃at the end of the 21th century is investigated using the SSP1-2.6 scenario from Coupled Model Intercomparison Program Phase 6(CMIP6).The multi-model ensemble mean suggests the NA summer monsoon precipitation will be increased by 0.26 mm/d relative to 1985—2014 under stabilized global warming of 1.5℃,yields the monsoon hydrological sensitivity of 4.8%/℃.The change of monsoon precipitation is more pronounced over the northern part of the NA monsoon region.The moisture budget analysis revealed that the thermodynamics processes increase the atmospheric temperature and enhance moisture transport,leading to the higher atmospheric precipitable water relative to 1985—2014 in the whole NA monsoon region.In the dynamic perspective,the significant warming over the Sahara region increases the land-sea thermal contrast and alters the zonal mean temperature structure.The former enhances the low-troposphere monsoon circulation,and the latter pushes the African Easterly Jet northward,resulting in enhanced monsoon precipitation over the northern part of the NA monsoon region.It is partially canceled by the weakened upper Tropical Easterly Jet,especially over the southern NA monsoon region.Thus,the dynamic processes shape the inhomogeneous change of monsoon precipitation.Therefore,the thermodynamic processes increase the regional mean monsoon precipitation,and the dynamic processes contribute to the spatial pattern of precipitation changes.

关 键 词：全球稳定增温 增温1.5℃ 北非夏季风降水 季风环流 

分 类 号：P426.6[天文地球—大气科学及气象学]