Key Environmental Factors for Rapid Intensification of the South China Sea Tropical Cyclones

Yao Chen,Si Gao,Xun Li,Xinyong Shen

doi:10.3389/feart.2020.609727

Abstract

Forecasting rapid intensification (RI) of the South China Sea (SCS) tropical cyclones (TCs) remains an operational challenge, mainly owing to the incomplete understanding of its physical mechanisms. Based on TC best-track data, atmospheric analysis data, and sea surface temperature data, this study compares temporal evolution characteristics of environmental conditions from the previous 24 h to the onset time for RI and non-RI TCs in the SCS during 2000–2018, and then identifies key factors for RI of the SCS TCs using the box difference index and stepwise regression. A combination of strong divergence in the upper troposphere and strong convergence in the boundary layer, weak deep-layer vertical wind shear, fast storm translation speed, and high TC intensification potential (i.e., maximum potential intensity minus current intensity) north of the storm center at the previous 24 h are favorable for RI of the SCS TCs, and their importance for RI is in descending order. The results may shed light on operational forecasting of rapid intensification of the SCS TCs.

Highlights

The South China Sea (SCS) is the largest semi-closed sea in the tropical western Pacific
The adjustment of the East Asian summer monsoon can strengthen the interactions between tropical cyclones (TCs) and the upper-level trough, and make the water vapor flux accompanied by the monsoon surge enter the TC circulation, preventing the dry air accompanied by the western Pacific subtropical high (WPSH) from intruding into the TC circulation
We investigate the temporal evolution characteristics of potential environmental factors during a 24 h period before the onset of TC rapid intensification (RI) in the SCS, so as to find the indicative precursors and the key influence areas of significant factors by composite analyses

Summary

INTRODUCTION

The South China Sea (SCS) is the largest semi-closed sea in the tropical western Pacific. The adjustment of the East Asian summer monsoon can strengthen the interactions between TCs and the upper-level trough, and make the water vapor flux accompanied by the monsoon surge enter the TC circulation, preventing the dry air accompanied by the western Pacific subtropical high (WPSH) from intruding into the TC circulation. This research is expected to provide some references for the operational intensity prediction of the SCS TCs. The TC information at a 6 h interval (latitude and longitude of the TC center and the maximum sustained wind speed) is obtained from the TC best-track dataset (Ying et al, 2014) released by the Shanghai Typhoon Institute of the China Meteorological Administration (CMA). We use the above datasets during our study period 2000–2018

Method

Findings

CONCLUSION AND DISCUSSION