副极地海洋锋区海温异常影响厄尔尼诺的机制研究  

Study on the mechanism of SST anomaly in the subarctic frontal zone impacting El Nio

作　　者：黄琼慧 房佳蓓[1] 杨修群[1] HUANG Qionghui;FANG Jiabei;YANG Xiuqun(School of Atmospheric Science,Nanjing University,Nanjing 210023,China)

机构地区：[1]南京大学大气科学学院,南京210023

出　　处：《气象科学》2023年第3期285-295,共11页Journal of the Meteorological Sciences

基　　金：国家重点研发计划资助项目(2022YFF0801702,2022YFE0106600)。

摘　　要：基于1979—2021年的ERA5再分析资料,研究了副极地海洋锋区(Subarctic Frontal Zone,SAFZ)海温(Sea Surface Temperature,SST)异常相关的冬季海气相互作用过程及其影响次年冬季厄尔尼诺(El Ni o)的机制。研究表明,冬季SAFZ的特征海气异常表现为大尺度的SST暖异常与偶极型的大气环流异常。在SAFZ海气相互作用过程中,海洋首先通过直接的非绝热加热影响低层大气斜压性,随后通过间接的瞬变涡旋反馈使相当正压的位势高度异常在整个冬季内维持。其中,南部的气旋式环流异常通过减弱副热带的平均信风激发太平洋经向模态(Pacific Meridional Mode,PMM)与风—蒸发—SST(Wind-Evaporation-SST,WES)反馈,从而使中纬度SST暖异常南传至热带太平洋中部,随后导致El Ni o发生。然而,并非所有的SAFZ暖异常事件都能激发次年冬季的El Ni o,中纬度海气耦合异常的初始配置及同期热带太平洋的表现情况将对中纬度信号南传至热带的过程产生较大的影响。Based on ERA5 reanalysis data from 1979 to 2021,the present study investigates the wintertime air-sea interaction process associated with Sea Surface Temperature(SST)anomaly in the Subarctic Frontal Zone(SAFZ)and the mechanism of how it impacts El Nio in the following winter.Result has shown that the characteristics of air-sea anomaly in SAFZ manifest as large-scale warm SST anomaly and dipole type anomaly in atmospheric circulation.During the air-sea interaction process,the ocean first affects the low-level atmospheric baroclinicity through direct diabatic heating and then helps to maintain the equivalent barotropic geopotential height anomaly throughout the winter by indirect transient eddy feedback.The cyclonic anomaly in the south stimulates the Pacific Meridional Mode(PMM)and the Wind-Evaporation-SST(WES)feedback by weakening the mean trade winds in subtropical Pacific,thereby causing the warm SST anomaly at midlatitudes to propagate down to the central tropical Pacific,and subsequently leading to the occurrence of El Nio.However,not all SAFZ events can trigger El Nio in the following winter.The initial configuration of midlatitude air-sea coupled anomaly and the circumstance of tropical Pacific at the same time would significantly impact the process of midlatitude signals being transmitted to the tropics.

关 键 词：副极地海洋锋区 海温异常 海气相互作用 太平洋经向模态 厄尔尼诺 

分 类 号：P732[天文地球—海洋科学]