Atmospheric diabatic heating–induced wave train from the Caspian Sea to South and East Asia during the summer monsoon season

ABSTRACT

During the summer monsoon season, the authors observe a wave train that stretches from the northern Arabian Peninsula and Caspian Sea to the Indo-Gangetic plains along the foothills of the Himalaya and extending further east of the Tibetan Plateau. The trend analysis between 1979 and 2018 with NCEP–NCAR reanalysis data show that the diabatic heating flux (averaged over 1000 to 500 hPa) tends to decrease significantly over the Caspian Sea and its surrounding regions. In addition, the sea level pressure is increasing by ~0.1 hPa yr⁻¹ over the Caspian Sea, forming a high-pressure divergent center over there. The divergent center is collocated with an anticyclonic circulation trend at 850 hPa over the Caspian Sea. This decreasing diabatic heating flux modulates the local atmospheric circulation by increasing the surface pressure around the center of divergence, which further facilitates a wave train to propagate towards South and East Asia. This wave train transports the moisture fluxes at 925 hPa from the Caspian Sea, southeastward towards the South and East Asian monsoon region.

GRAPHICAL ABSTRACT

摘要

本研究发现在夏季风季, 存在从阿拉伯半岛北部和里海至印支恒河平原的一个波列, 该波列进一步沿喜马拉雅山麓伸展到青藏高原东部。利用NCEP–NCAR再分析资料计算的大气非绝热加热通量 (1000 hPa至500 hPa 平均) 在里海及其周围地区表现出从1979至2018年的显著的减少趋势。而海平面气压在里海地区则呈现出大约0.1 hPa yr⁻¹的增加趋势, 并在该区域形成一个高压的辐散中心。这个辐散中心正与里海上空850 hPa的一个反气旋环流趋势相配。减少的大气非绝热通量通过地面气压在辐散中心附近的增加可以调控当地的大气环流, 并进而激发传播向南亚和东亚的波列。该波列可以将925 hPa的水汽从里海向东南输送到南亚季风和东亚季风区。

KEYWORDS:

• Moisture transport
• wave train
• diabatic heating
• Indian summer monsoon
• Caspian Sea

关键词:

• 水汽输送
• 波列
• 非绝热加热
• 印度夏季风
• 里海

Disclosure statement

The authors declare no conflicts of interest.

SUPPLEMENTAL DATA

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Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was jointly supported by the Ministry of Science and Technology of China [grant number 2016YFA0600604], the National Natural Science Foundation of China [grant numbers 41950410756 and 41675061], and the Key Research Program of Frontier Sciences, Chinese Academy of Sciences [grant number QYZDY-SSW-DQC024].