期刊
GEOPHYSICAL RESEARCH LETTERS
卷 49, 期 23, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2022GL100976
关键词
monsoon; low-pressure systems; extratropical air intrusions; stratospheric dynamics; Rossby waves
资金
- IISER Pune
- MHRD, Government of India
- DST-SERB, Government of India
- Ministry of Earth Sciences, Government of India
- [DST-INSPIRE]
Low-pressure systems make a significant contribution to the summer monsoon rainfall in the Indian subcontinent, with a portion of them being amplified by disturbances from the western North Pacific. Analysis shows that 43% of these amplifications are caused by extratropical stratospheric air intrusions, which lead to high tropospheric potential vorticity and initiate and intensify low-level cyclonic vortices.
Low-pressure systems (LPS) are convectively coupled vortices that contribute nearly half of the summer monsoon rainfall over the Indian subcontinent. About one third of the boreal summer monsoon LPS are caused by downstream amplification of westward propagating disturbances from the western North Pacific (WNP). Analysis of downstream LPS events from 1979 to 2017 reveals that 43% of them are caused by extratropical stratospheric air intrusions over the WNP. Stratospheric air intrusions lead to high tropospheric potential vorticity (PV), and the downstream vortex seeds are observed to initiate and intensify to the southwest of the PV anomalies. The PV anomalies can deform the temperature in its neighborhood and cause adiabatic lifting, which in turn can induce and intensify low-level cyclonic vortices. The subsequent intensification of the low-level vortex is aided by deep convection, observed to the southwest of the PV anomaly, through vortex stretching and low-level PV generation by diabatic heating.
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