Seasonal and Regional Signatures of ENSO in Upper Tropospheric Jet Characteristics from Reanalyses
Seasonal and Regional Signatures of ENSO in Upper Tropospheric Jet Characteristics from Reanalyses
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DOI：
10.1175/jcli-d-20-0947.1
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发表时间：
2021-11-01
影响因子：
4.9
通讯作者：
Lawrence, Zachary D.
中科院分区：
文献类型：
--
作者：
Manney, Gloria L.;Hegglin, Michaela I.;Lawrence, Zachary D.
分析了1979-2018年再分析资料集上对流层高空急流变率与厄尔尼诺-南方涛动(ENSO)的关系，揭示了较强的区域和季节变率。与季风和Walker环流相关的热带急流较弱，在厄尔尼诺期间，两个半球的纬向平均副热带急流向赤道方向移动，这与以前的发现一致。对副热带急流和极地急流的区域和季节变化分别进行了分析。在厄尔尼诺期间，副热带急流在12-2月期间在北半球(NH)东太平洋(DJF)上空向极地移动，在3-5月和9-11月(SON)在一些南半球(SH)地区向极地转移。厄尔尼诺期间副热带急流高度增加，NH区纬向平均高度变化明显，SH区夏季/秋季变化明显。虽然纬向平均极地急流与ENSO的相关性很小，但区域/季节变化很明显：在厄尔尼诺期间，在亚洲和西太平洋的DJF，SH极地急流向赤道移动，在6-8月和SON期间，在东太平洋显著地向极地移动。厄尔尼诺期间，极地急流在西半球较弱，在东半球较强，特别是在SH；相反，在冬季和春季厄尔尼诺期间，副热带急流在西半球较强，在东半球较弱。这些相反的变化，以及副热带和极地急流风速之间的反相关，加强了厄尔尼诺期间副热带-极地急流强度的差异，并表明这些急流与ENSO有关。与ENSO相关的急流纬度、高度和风速变化，副热带急流分别为4度、0.6公里和6ms(-1)，极地急流分别为3度、0.3公里和3ms(-1)。
The relationship of upper tropospheric jet variability to El Nino-Southern Oscillation (ENSO) in reanalysis datasets is analyzed for 1979-2018, revealing robust regional and seasonal variability. Tropical jets associated with monsoons and the Walker circulation are weaker and the zonal mean subtropical jet shifts equatorward in both hemispheres during El Nino, consistent with previous findings. Regional and seasonal variations are analyzed separately for subtropical and polar jets. The subtropical jet shifts poleward during El Nino over the Northern Hemisphere (NH) eastern Pacific Ocean in December-February (DJF) and in some Southern Hemisphere (SH) regions in March-May and September-November (SON). Subtropical jet altitudes increase during El Nino, with significant changes in the zonal mean in the NH and during summer/autumn in the SH. Although zonal mean polar jet correlations with ENSO are rarely significant, robust regional/seasonal changes occur: The SH polar jet shifts equatorward during El Nino overAsia and the western Pacific in DJF and significantly poleward over the eastern Pacific in June-August and SON. During El Nino, polar jets are weaker in the Western Hemisphere and stronger in the Eastern Hemisphere, especially in the SH; conversely, subtropical jets are stronger in the Western Hemisphere and weaker in the Eastern Hemisphere during El Nino in winter and spring. These opposing changes, along with an anticorrelation between subtropical and polar jet wind speeds, reinforce subtropical-polar jet strength differences during El Nino and suggest ENSO-related covariability of the jets. ENSO-related jet latitude, altitude, and wind speed changes can reach 4 degrees, 0.6km, and 6ms(-1), respectively, for the subtropical jets and 3 degrees, 0.3km, and 3ms(-1), respectively, for the polar jets.