Effects of ocean eddies on the tropical storm Roanu intensity in the Bay of Bengal.

Yujun Liu,Xueting Xing,Haibin Lü,Yusheng Cui,Honghua Zhang,João Miguel Dias

doi:10.1371/journal.pone.0247521

Abstract

A tropical storm (TS) Roanu occurred in northern Sri Lanka in 2016, which transported northwards along the west coast of the Bay of Bengal (BoB). During the development of the TS, ocean eddies on its track had an important effect on the intensity of Roanu. The dynamic mechanism was investigated with multisource reanalysis and Argo float data in this study. The results show that ocean eddies were the main reason why Roanu first enhanced, weakened, and then enhanced again. Warm eddy W1 supports the initial development of the TS, cold eddy C1 weakens Roanu, and warm eddy W2 continues to support Roanu. On May 19, 2016, the maximum average latent heat flux over W1 was 260.85 w/m2, while that of C1 was only 200.71 w/m2. After the passage of Roanu, the tropical cyclone heat potential (TCHP) of eddies significantly decreased. The TCHP of W1, W2, C1 and C2 decreased by 20.95 kJ/cm2, 11.07 kJ/cm2, 29.82 kJ/cm2, 9.31 kJ/cm2, respectively. The mixed layer of warm eddies deepened much more than that of cold eddies, supporting Roanu development. In addition, changes in potential vorticity (PV) values caused by the disturbance of eddies may also reflect changes in the TS intensity. This study offers new insights on the influence of ocean eddies in regulating the development of tropical cyclone (TC) in the BoB.

Highlights

A tropical cyclone (TC) is a strong cyclonic vortex with a warm central structure commonly found over tropical and subtropical oceans
A similar phenomenon appeared in Atlantic tropical cyclone genesis events [41], Fig 2B and 2D show the geopotential height field and wind field distribution of the tropical storm (TS) at 950 mb
Bay of Bengal (BoB) was mainly controlled by low pressure levels at 950 mb, forming an obvious trough was surrounded by the 51 dagpm isoline (Fig 2B)

Summary

Introduction

A tropical cyclone (TC) is a strong cyclonic vortex with a warm central structure commonly found over tropical and subtropical oceans. Less than 7% of global TCs occur in the Bay of Bengal (BoB), 80% of the world’s deadliest cyclones form in this bay [2]. TC activity in the BoB is highly seasonal, and TC is strongest after the monsoon season (October to December) as well as being stronger before the monsoon season (March to May) [3, 4].

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Discussion

Conclusion