Association of the shift of the South Asian high in June with the diabatic heating in spring
Association of the shift of the South Asian high in June with the diabatic heating in spring
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DOI：
10.1007/s00382-022-06161-z
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发表时间：
2022-02
期刊：
影响因子：
4.6
通讯作者：
S. Gui;Qin Su;Ruowen Yang;Jie Cao
中科院分区：
文献类型：
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作者：
S. Gui;Qin Su;Ruowen Yang;Jie Cao
本文定义了南亚高压（SAH）核心位置指数，并利用1979-2018年的相关分析和ERA-Interim再分析资料，识别了印度洋中部-青藏高原西南部春季潜热加热配置，通过表观水汽汇为6月SAH移动提供了主导信号。这些在北方春季的主导信号具有明确的物理意义，其特征在于印度洋中部（IO）和青藏高原西南部（SWTP）的纬向视水汽汇的对比。当春季IO中心和SWTP之间的表观水汽汇对比高于正常时，加热型诱导异常的垂直环流，增强了IO中心和SWTP之间的中层对流和高层辐散之间的耦合。6月前南亚高压路径上游的高层辐散环流有利于南亚高压的发展，因此6月南亚高压比常年偏西北。当春季表观水汽汇对比度低于正常值时，大气响应发生逆转，导致SAH向东南方向移动。数值试验证实了纬向表观水汽汇对比在IO-SWTP中心及其相关物理过程中的驱动作用。进一步的分析表明，3月下旬至5月下旬的表观水汽汇对比与6月的南亚高压纬向位置之间存在着显著而持久的相关性。因此，春季纬向表观水汽汇对比是预测6月南亚高压移动的合理预测因子。
In this paper, we define the index of the South Asian High (SAH) core position and use correlation analysis and ERA-Interim reanalysis data during 1979–2018 to identify spring latent heating configurations in the central Indian Ocean–southwestern Tibetan Plateau that provide leading signals for the SAH shift in June via the apparent moisture sink. These leading signals in boreal spring have a clear physical significance, and are characterized by a contrast in the meridional apparent moisture sink between the central Indian Ocean (IO) and the southwestern Tibetan Plateau (SWTP). When the spring apparent moisture sink contrast between the central IO and the SWTP is higher than normal, the heating pattern induces an anomalous vertical circulation that enhances the coupling between the mid-level convection and upper-level divergence over the central IO-SWTP. The upper-level divergent circulation in the upper reaches of the SAH track favors the development of the SAH before June, and thus the SAH shifts farther northwestward than normal in June. When the spring apparent moisture sink contrast is lower than normal, the atmospheric response is reversed, causing the SAH to shift farther southeastward than normal. Numerical experiments have confirmed the driving role of the meridional apparent moisture sink contrast in the central IO-SWTP and the associated physical processes. Further analyses reveal a significant and persistent correlation between the apparent moisture sink contrast in late March to late May and the SAH meridional position in June. The spring meridional apparent moisture sink contrast is therefore a reasonable predictor in forecasting the SAH shift in June.