Interdecadal change in the influence of the southern annular mode to the tropical cyclone frequency over the Bay of Bengal

IF 3.5 3区 地球科学 Q2 METEOROLOGY & ATMOSPHERIC SCIENCES
Dickson Mbigi, Ziniu Xiao
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Abstract

The current study investigates the modulation of the tropical cyclone (TC) frequency (TCF) over the Bay of Bengal (BoB) by the southern annular mode (SAM). The analysis reveals that the SAM–TCF relationship during October–November–December has undergone interdecadal changes from significant during 1971–1994 to insignificant during 1995–2021. This contrasting influence of the SAM on the TCF occurrence is also echoed in the large-scale environmental variables conducive to forming tropical cyclones (TCs). Based on the possible mechanism, we found that the SAM can imprint tripole sea surface temperature (SST) patterns in the southern Indian Ocean via altering surface wind speed from 1971 to 1994. The SAM-related tripole SST pattern induces the surface-level anticyclone anomaly, which enhances the south easterlies towards the western equatorial Indian Ocean. Such intensified anomalous wind crosses the equator and diverts towards the east to form the cyclone anomaly in the BoB. Meanwhile, at 200 hPa, the anomalous anticyclone over western Australia induces divergent wind flows over the study region. Consequently, the ascending motion in BoB promotes the tropical cyclone generation. During 1995–2021, however, the SAM is associated with the dipole SST pattern in the southern Indian Ocean. Correspondingly, the SAM-related dipole SST yields anomalous atmospheric circulations confined to the Southern Hemisphere and eventually fails to impact the formation of TCs in the northern Indian Ocean, where the study region is located. The findings of this research can be useful in advancing our knowledge of the interannual variability of TCs activity in the BoB based on the remote climate signal.

Abstract Image

南环流模式对孟加拉湾热带气旋频率影响的年代际变化
本研究调查了南部环流模式(SAM)对孟加拉湾热带气旋频率(TCF)的调制作用。分析表明,在 10 月-11 月-12 月期间,SAM 与 TCF 的关系经历了从 1971-1994 年期间的显著到 1995-2021 年期间的不显著的年代际变化。热带气旋形成的大尺度环境变量也反映了SAM对TCF发生的反差影响。根据可能的机制,我们发现从 1971 年到 1994 年,SAM 可以通过改变表面风速来影响南印度洋的三极海面温度(SST)模式。与萨米山脉有关的三极海面温度模式诱发了海面反气旋异常,从而增强了向赤道印度洋西部的东南风。这种增强的异常风穿过赤道后转向东方,在 BoB 形成气旋异常。同时,在 200 hPa,澳大利亚西部上空的异常反气旋在研究区域诱发了发散风流。因此,BoB 的上升运动促进了热带气旋的生成。然而,在 1995-2021 年期间,SAM 与南印度洋的偶极 SST 模式有关。相应地,与萨马拉模式相关的偶极 SST 产生的异常大气环流仅限于南半球,最终未能影响研究区域所在的北印度洋热带气旋的形成。这项研究的结果有助于我们根据遥远的气候信号加深对 BoB 热带气旋活动年际变率的了解。
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来源期刊
International Journal of Climatology
International Journal of Climatology 地学-气象与大气科学
CiteScore
7.50
自引率
7.70%
发文量
417
审稿时长
4 months
期刊介绍: The International Journal of Climatology aims to span the well established but rapidly growing field of climatology, through the publication of research papers, short communications, major reviews of progress and reviews of new books and reports in the area of climate science. The Journal’s main role is to stimulate and report research in climatology, from the expansive fields of the atmospheric, biophysical, engineering and social sciences. Coverage includes: Climate system science; Local to global scale climate observations and modelling; Seasonal to interannual climate prediction; Climatic variability and climate change; Synoptic, dynamic and urban climatology, hydroclimatology, human bioclimatology, ecoclimatology, dendroclimatology, palaeoclimatology, marine climatology and atmosphere-ocean interactions; Application of climatological knowledge to environmental assessment and management and economic production; Climate and society interactions
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