秋季ENSO与IOD对东亚副热带西风急流的协同影响  

Synergistic effects of ENSO and IOD on the East Asian subtropical westerly jet in autumn

作　　者：宋文君 李旭[1] 李艳[1] SONG Wen-jun;LI Xu;LI Yan(College of Atmospheric Sciences,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学大气科学学院,兰州730000

出　　处：《兰州大学学报（自然科学版）》2023年第5期610-619,共10页Journal of Lanzhou University(Natural Sciences)

基　　金：国家自然科学基金面上项目(41775051)。

摘　　要：利用美国国家环境预测中心/国家大气研究中心1979-2020年的再分析资料、Ni?o3.4、印度洋偶极子(IOD)和副热带西风急流(SWJ)指数,研究秋季厄尔尼诺-南方涛动(ENSO)和IOD对SWJ的协同影响及其机理.秋季SWJ强度、位置与ENSO和IOD存在显著相关,急流强度指数与Ni?o3.4和IOD指数的相关系数分别为-0.32和-0.31;急流轴指数与Ni?o3.4和IOD指数的相关系数分别为-0.75和-0.34,即当ENSO和IOD位于正(负)位相时,SWJ减弱(加强),急流位置偏南(北).ENSO和IOD事件对SWJ具有协同影响,表现为ENSO和IOD暖位相或冷位相会同时发生,且ENSO和IOD暖事件或冷事件共同发生时对SWJ的影响较其单独作用有放大效应,即当ENSO和IOD正(负)位相共同发生时,SWJ减弱(增强)幅度更大.ENSO和IOD事件可通过大气斜压性和Hadley环流影响SWJ.当ENSO和IOD正事件共同发生时,200~500 hPa处的经向气温梯度出现负异常,纬向风速随高度增加增大得更慢,使SWJ减弱;Hadley环流在不同ENSO和IOD事件协同影响下也有所不同,相较于ENSO和IOD处于正位相,当La Ni?a和IOD负位相共同发生时,Hadley环流上升支的强度更强且上升位置更高,携带更多地球角动量进入SWJ,使急流加强.The synergistic effects of El Niño-Southern oscillation(ENSO)and Indian Ocean dipole(IOD)on the subtropical westerly jet(SWJ)in autumn and their mechanisms were investigated by using the National Centers for Environmental Prediction and National Center for Atmospheric Research of American reanalysis data during 1979-2020,Niño3.4,IOD and SWJ index.The correlation coefficients of SWJ strength index with the Niño3.4 and IOD indices were-0.32 and-0.31 respectively,and the correlation coefficients of the jet axis index with the Niño3.4 and IOD indices were-0.75 and-0.34 respectively,i.e.when the ENSO and IOD were in a positive(negative)phase,SWJ weakened(strengthened)and the jet was located to the south(north).ENSO and IOD events had a synergistic effect on SWJ,as shown by the simultaneous occurrence of ENSO and IOD warm or cold phases,when the ENSO and IOD warm or cold events together had a greater effect on SWJ than when they acted separately,i.e.when ENSO and IOD positive(negative)phases occurred together,SWJ weakened(strengthened)to a greater extent.Further research proved that ENSO and IOD events could influence SWJ through atmospheric instability and the Hadley circulation.When ENSO and IOD positive events occurred together,there was a negative spatial leveling of upper tropospheric temperatures,a negative difference in the longitudinal temperature gradient over 200-500 hPa,and a slower increase in latitudinal winds with increasing height.The Hadley circulation also varied between ENSO and IOD events.Under La Niña and IOD negative phase,the upward branch of the Hadley circulation was stronger and in a higher position than when ENSO and IOD were in a positive phase,carrying more of the Earth's angular momentum into SWJ rapids,and causing the jet to strengthen.

关 键 词：印度洋偶极子 厄尔尼诺-南方涛动 副热带西风急流 大气斜压性 协同影响 

分 类 号：P44[天文地球—大气科学及气象学]