热带海面温度对亚马逊旱季降水年际变率的影响及机制  

Effect of the Tropical Sea Surface Temperature on the Interannual Rainfall Variability and Its Mechanism over the Amazon in the Dry Season

作　　者：刘映雪 胡开明[1,3,4] 黄刚 LIU Yingxue;HU Kaiming;HUANG Gang(State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029;University of Chinese Academy of Sciences,Beijing 100049;Joint Center for Global Change Studies,Beijing 100875;Center for Monsoon System Research,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100190)

机构地区：[1]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029 [2]中国科学院大学,北京100049 [3]全球变化研究协同创新中心,北京100875 [4]中国科学院大气物理研究所季风系统研究中心,北京100190

出　　处：《气候与环境研究》2022年第2期263-275,共13页Climatic and Environmental Research

基　　金：国家重点研发计划2019YFA0606703;中国科学院战略性先导科技专项XDA20060502;国家自然科学基金41775086、41831175。

摘　　要：用偏最小二乘(Partial Least Square,PLS)回归方法分析了1979~2018年影响亚马逊旱季(6~8月)降水年际变率的热带海面温度模态。第一海面温度模态解释了总方差的64%,主要表现为前期亚马逊雨季(12月至次年2月)至旱季(6~8月)热带东太平洋La Niña型海面温度异常演变。12月至次年2月热带东太平洋出现La Niña型海面温度冷异常;3~5月热带东太平洋冷异常增强,并在热带印度洋、热带北大西洋出现冷异常,在热带南大西洋有暖异常;6~8月热带东太平洋冷异常向东收缩;9~11月整个热带海面温度异常均快速衰退。第二海面温度模态解释了总方差的19%,主要表现为前期亚马逊雨季(12月至次年2月)至旱季(6~8月)中太平洋Modoki El Niño型增暖。12月至次年2月在热带中太平洋出现暖异常,印度洋和南大西洋同样也出现暖异常,热带中太平洋和南大西洋暖异常能持续到9~11月,而印度洋暖异常在9~11月衰减。这些结果表明,亚马逊旱季降水与热带海面温度的演变有关,当前期12月至次年2月出现La Niña(Modoki El Niño)事件、3~8月出现热带南北大西洋海面温度梯度负异常并且热带印度洋海面温度冷(暖)异常时,亚马逊旱季降水偏多。这两个海面温度模态对降水的总贡献与亚马逊旱季降水指数的相关关系高达0.92,说明亚马逊旱季降水年际变率与热带海面温度密切相关;而且这两个海面温度模态对亚马逊旱季降水的贡献还有明显的年代际变化,自1979年以来,海面温度对降水的贡献有下降趋势。还对海面温度影响亚马逊旱季降水年际变率的机制进行了分析,发现海面温度可以通过影响亚马逊地区的环流场、水汽输送以及大气对流层稳定性进而导致降水异常。第一海面温度模态能激发亚马逊低空北部气流辐合,高空北部气流辐散,容易形成异常的上升运动;同时,亚马逊对流层的异常湿静能收支也表明第一海面温�Using the PLS(partial least square)regression method,the leading tropical Sea Surface Temperature(SST)modes that affect the interannual rainfall variability over the Amazon in the dry season(June–August,JJA)in 1979–2018 were analyzed.The first SST mode features a decaying La Niña-like cooling in the tropical eastern Pacific from the preceding rainy season(December–February,DJF)to the dry season(JJA),explaining 64%of the total variance of the rainfall.Anomalous cooling appears in the tropical eastern Pacific in DJF and develops in March–May(MAM).Meanwhile,the tropical Indian Ocean and North Atlantic also become cooler and the tropical south Atlantic becomes warmer.The cooling in the Pacific decreases in JJA,but the anomalous SST still exists in other oceans.Finally,all anomalous SSTs decay in September–November(SON).The second SST mode exhibits anomalous warming in the central Pacific from the preceding rainy season to the dry season,explaining 19%of the total variance.There is anomalous warming in the tropical central Pacific,south Atlantic,and the Indian Ocean,which exists from DJF to SON in the Pacific and Atlantic but decays during SON in the Indian Ocean.This suggests that the interannual rainfall variability over the Amazon in the dry season is related to the evolution of the tropical SST.The evolution of La Niña(Modoki El Niño)starting from the preceding DJF,the anomalous negative temperature gradient between the tropical North Atlantic and South Atlantic,and cooling(warming)in the tropical Indian Ocean in March–August all lead to increased rainfall over the Amazon.The two SST modes’contribution is closely related to the rainfall index,with their correlation coefficient reaching 0.92.In addition,the contributions have experienced interdecadal changes with a considerable decline during 1979–2018.Moreover,this study investigated the mechanism of the leading SST modes affecting the interannual rainfall variability over the Amazon in the dry season,which indicates that the SST modes are criti

关 键 词：热带海温模态 亚马逊旱季降水 El Niño 事件 AMIP6模式 

分 类 号：P461.2[天文地球—大气科学及气象学]