Tropical and Extratropical Influences on the Variability of the Southern Hemisphere Wintertime Subtropical Jet
Tropical and Extratropical Influences on the Variability of the Southern Hemisphere Wintertime Subtropical Jet
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热带和温带对南半球冬季副热带急流变化的影响
DOI：
10.1175/jcli-d-20-0460.1
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发表时间：
2021
影响因子：
4.9
通讯作者：
E. Lim
中科院分区：
文献类型：
--
作者：
Z. E. Gillett;H. Hendon;J. Arblaster;E. Lim
使用 1979 年至 2018 年期间的大气再分析来评估南半球副热带急流 (STJ) 的年际变化。重点是南方冬季，此时 STJ 最强，与中纬度涡流驱动急流 (EDJ) 最为明显。 STJ 的强度和纬度位置的变化可以使用为区分与 EDJ 相关的变化而开发的指数来诊断。研究发现 STJ 强度和位置变化与不同的机制有关。 STJ 的强化与赤道太平洋上空非绝热加热的辐散外流增强有关，这主要是由东太平洋或典型厄尔尼诺现象造成的。这种强化与 STJ 的缩小和 EDJ 的就地减弱有关。然而，向赤道移动的 STJ 似乎是涡流驱动的，并且与 EDJ 的加速和极向位移相关，EDJ 投射到南环模态的正极性上。正如之前报道的，厄尔尼诺莫多基（或中太平洋厄尔尼诺）可能会在南半球冬季使 EDJ 向极地移动；因此，STJ 位置变化的一个可能途径是通过热带强制 EDJ 位置的变化。与之前的研究相比，我们还强调了与哈德利环流扩张相关的 STJ 的减弱和向极地移动。
Interannual variability of the Southern Hemisphere subtropical jet (STJ) is assessed using atmospheric reanalyses during 1979–2018. The focus is on the austral winter season when the STJ is strongest and most distinct from the midlatitude eddy-driven jet (EDJ). Variations in the intensity and latitudinal position of the STJ are diagnosed using an index developed to discriminate between variations associated with the EDJ. STJ intensity and position variations are found to be tied to different mechanisms. An intensification of the STJ is associated with enhanced divergent outflow from diabatic heating over the equatorial Pacific Ocean, primarily resulting from eastern Pacific or canonical El Niño. This intensification is associated with a narrowing of the STJ and an in-place weakening of the EDJ. An equatorward-shifted STJ, however, appears to be eddy driven and is associated with an acceleration and poleward displacement of the EDJ, which projects onto the positive polarity of the southern annular mode. As has previously been reported, El Niño Modoki (or central Pacific El Niño) can act to shift the EDJ poleward during austral winter; thus, a possible pathway for changes in the position of the STJ is via tropically forced changes in the position of the EDJ. In contrast to previous studies, we also highlight a weakening and poleward shift of the STJ in association with an expansion of the Hadley circulation.
影响因子：
4.9
作者：
Maycock A
通讯作者：
Maycock A
副热带急流正在向极地移动吗？
影响因子：
4.6
作者：
Maher P
通讯作者：
Maher P