Role of Intraseasonal Oscillation in Linking the Stepwise Onset of Summer Monsoon in the Northern Indian Ocean

IF 2 4区 地球科学 Q3 METEOROLOGY & ATMOSPHERIC SCIENCES
Kuiping Li, Qin He, Yang Yang
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引用次数: 0

Abstract

The summer monsoon onset in the northern Indian Ocean is crucial for the densely populated South Asia, as it ends the pre-monsoon heatwave and kicks off the rainy agricultural season. Climatologically, this onset occurs in two distinct phases: first in the Bay of Bengal (BoB), followed by the Arabian Sea (AS). However, the possible mechanistic linkage between these phases remains unclear. Based on observational analysis, this study investigates how the BoB monsoon onset preconditions the subsequent AS monsoon onset, with particular focus on the pivotal trigger of the AS monsoon—the intraseasonal oscillation (ISO-AS). We demonstrate that the BoB monsoon onset establishes an easterly vertical wind shear across the northern Indian Ocean. The shear environment interacts with the ascending motion of the ISO-AS, which develops approximately 1 month later, enhancing cyclonic vorticity north of the convection center of the ISO-AS. This process, in turn, promotes moisture convergence in the boundary layer and facilitates the northward propagation of the ISO-AS, ultimately triggering the summer monsoon onset in the AS. By elucidating the stepwise nature of monsoon onset in the northern Indian Ocean, this work offers valuable insights for improving predictions of the Asian summer monsoon.

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季节内振荡在连接北印度洋夏季风逐步爆发中的作用
北印度洋的夏季季风对人口稠密的南亚至关重要,因为它结束了季风前的热浪,开启了多雨的农业季节。从气候学上讲,这种开始分两个不同的阶段:首先在孟加拉湾(BoB),其次是阿拉伯海(AS)。然而,这些阶段之间可能的机制联系仍不清楚。在观测分析的基础上,本研究探讨了南亚季风的爆发如何成为随后南亚季风爆发的先决条件,并特别关注了南亚季风的关键触发因素——季内涛动(ISO-AS)。我们证明了BoB季风的开始在印度洋北部建立了一个偏东的垂直风切变。切变环境与ISO-AS上升运动相互作用,在大约1个月后发展,增强了ISO-AS对流中心以北的气旋涡度。这一过程反过来又促进了边界层水汽辐合,促进了ISO-AS向北传播,最终引发了夏季风在AS的爆发。通过阐明北印度洋季风发生的阶梯性,这项工作为改进亚洲夏季风的预测提供了有价值的见解。
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来源期刊
Atmospheric Science Letters
Atmospheric Science Letters METEOROLOGY & ATMOSPHERIC SCIENCES-
CiteScore
4.90
自引率
3.30%
发文量
73
审稿时长
>12 weeks
期刊介绍: Atmospheric Science Letters (ASL) is a wholly Open Access electronic journal. Its aim is to provide a fully peer reviewed publication route for new shorter contributions in the field of atmospheric and closely related sciences. Through its ability to publish shorter contributions more rapidly than conventional journals, ASL offers a framework that promotes new understanding and creates scientific debate - providing a platform for discussing scientific issues and techniques. We encourage the presentation of multi-disciplinary work and contributions that utilise ideas and techniques from parallel areas. We particularly welcome contributions that maximise the visualisation capabilities offered by a purely on-line journal. ASL welcomes papers in the fields of: Dynamical meteorology; Ocean-atmosphere systems; Climate change, variability and impacts; New or improved observations from instrumentation; Hydrometeorology; Numerical weather prediction; Data assimilation and ensemble forecasting; Physical processes of the atmosphere; Land surface-atmosphere systems.
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