北太平洋维多利亚模态(VM)与海洋性大陆秋季降水年际关系的年代际变化  

The Interdecadal Shift of Interannual Relationship between Victoria Mode in the North Pacific and Autumn Precipitation over the Maritime Continent

作　　者：朱科旭 任保华[1] 郑建秋[1] ZHU Kexu;REN Baohua;ZHENG Jianqiu(School of Earth and Space Science‚University of Science and Technology of China,Hefei 230026)

机构地区：[1]中国科学技术大学地球和空间科学学院,合肥230026

出　　处：《大气科学》2024年第4期1444-1456,共13页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金项目41675066。

摘　　要：本文利用HadISST和ERSSTv5海表温度、EN4次表层海温数据、CMAP降水和ERA5再分析资料,研究了北太平洋春季海表温度与海洋性大陆秋季降水年际变化之间的关系及年代际变化特征。研究表明:(1)北太平洋维多利亚模态(VM)是北太平洋春季海表温度EOF第二模态,其与秋季海洋性大陆的降水存在显著的负相关关系。(2)春季的VM为正(负)位相时,通常伴随太平洋经向模态的正(负)位相和西北太平洋的冷(暖)海表温度异常,海表温度梯度会导致赤道太平洋的西风(东风)异常,影响东传的赤道开尔文波,在赤道中东太平洋形成暖(冷)海温异常,再通过Bjerknes正反馈,西风异常和赤道中东太平洋的海温异常维持到秋季,秋季时出现较成熟的厄尔尼诺(拉尼娜)事件。再通过沃克环流,海洋性大陆出现异常下沉(上升)运动和低层辐散、高层辐合(低层辐合、高层辐散)的环流形势,产生降水负(正)异常。(3)春季的VM和秋季的海洋性大陆降水年际变化的关系在2003年发生了年代际转变,1979~2002年春季VM与秋季降水在年际变化上有显著的负相关,而2004~2020年相关关系转变为不显著。造成这个年代际转变的原因是北太平洋涛动(NPO)在2004~2020年强度减弱、位置移动,导致VM南部海表温度关键区受NPO的影响减弱,从而振幅减弱,使得VM的南部和北部海表温度关键区的经向梯度减弱,VM强度减弱,最终导致相关系数降低。Based on the HadISST and ERSSTv5 sea surface temperature(SST)data,EN4 subsurface ocean temperature data,CMAP precipitation,and ERA5 reanalysis data,this paper presents the interdecadal shift of the interannual relationship between spring SST in the North Pacific and autumn precipitation in the Maritime Continent.(1)Victoria mode(VM)is the second mode of EOF analysis of spring SST in the North Pacific,which has a significant negative correlation with autumn precipitation in the Maritime Continent.(2)When VM is in a positive(negative)phase in spring,it is usually accompanied by the positive(negative)phase of the Pacific meridional mode and the cold(warm)SST anomaly in the Western North Pacific.The SST gradient would result in the westerly(easterly)anomaly in the equatorial Pacific,affecting the eastward propagation of the equatorial Kelvin wave and leading to warm(cold)SST anomaly in the central and eastern Pacific.The SST gradient and westerly(easterly)anomaly persist into autumn through Bjerknes feedback;thus,the mature El Niño(La Niña)event forms in autumn.Afterward,via the Walker circulation,the abnormal sinking(rising)movement and low-level divergence and high-level convergence(low-level convergence and high-level divergence)over the Maritime Continent take place,causing a precipitation decrease(increase).(3)This interannual relationship between the variation of springtime VM and the autumn precipitation over the Maritime Continent changed in 2003,which was a significant negative correlation for the period 1979-2002 but was insignificant in 2004-2020.This interdecadal shift is because the magnitude and position of the North Pacific Oscillation changed in 2004-2020,leading to the weakening of the influence of the North Pacific Oscillation on the southern SST key area of VM,thus weakening the amplitude,weakening the meridional gradient of the key area of SST between the southern and northern part of VM,weakening the VM amplitude,and finally reducing the correlation coefficient.

关 键 词：北太平洋维多利亚模态 海洋性大陆 秋季降水 北太平洋涛动 年代际转变 

分 类 号：P467[天文地球—大气科学及气象学]