Numerical simulation of tropical cyclone generated waves in South China Sea during winter monsoon surge

Peng Qi,Aimei Wang

doi:10.1038/s41598-020-79204-2

Abstract

The South China Sea (SCS) is a highly semi-enclosed marginal sea located in the East Asian monsoon region. This paper proposes interesting aspects of the unique feature of the SCS waves in response to tropical cyclone's passage when large-scale winter monsoon winds prevail. We use the wave model WaveWatch III to study the wave characteristics of typhoon Durian (2006) passing over the middle of SCS in early December 2006, and state the new understanding acquired in the aspects of the tropical cyclone generated waves in the SCS during winter monsoon surge. In light of this, the role of the large-scale NE monsoon winds on winter typhoon wave field characteristics in the SCS are highlighted by conducting sensitivity experiments with and without the NE monsoon winds. The NE monsoon winds weakly affect the SWH field near the typhoon track and strongly away from the track, especially in the deep water area of the northern SCS where the NE monsoon winds produce high waves. Comparisons between the two experiments show the effect of the NE monsoon winds on the directional wave spectra in the SCS, suggesting that the monsoon-generated swells do not decay and remain throughout the typhoon period.

Highlights

The South China Sea (SCS) is located at 0°–23° N, 99° E–121° E, with a total area of about 3.5 × 106 km[2]
The wave model NWW3 was forced by blended wind fields of the parametric model typhoon winds and the largescale NE monsoon winds [i.e., monsoon winds Ven ≠ 0 in Eq (4)] to hindcast the unique wave characteristics during TY Durian’s passage in the SCS in early December 2006
The first two snapshots in the upper panels (Fig. 4a,b), from 0600 to 1800UTC November 30, are monsoon- generated wave fields, which is mainly determined by wind speed, duration and fetch, especially a fetch-limited situation forced by the steady winter monsoon winds

Summary

Introduction

The South China Sea (SCS) is located at 0°–23° N, 99° E–121° E, with a total area of about 3.5 × 106 km[2]. The SCS is connected to the surrounding oceans by several straits: the western Pacific through Luzon Strait, the southern shelf of the East China Sea through Taiwan Strait, the Java Sea through Gasper and Karimata Straits, and to the Indian Ocean through the Straits of Malacca All of these straits are shallow except the Luzon Strait, the maximum depth of which is around 2000 m1. The effects of the typhoon and monsoon combined wind forcing on the wave characteristics are unique in the SCS, and may not be representative of the western North A tlantic[10]. A TC surface wind field can be produced by the mesoscale atmospheric numerical prediction model with many approximations in the air-sea interfaces. The Holland model can not accurately give the outer TC wind field due to its extension of the vortex wind field to infinity[22,23]

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Conclusion