Trends and drivers of tropical cyclones originating in the South China Sea during 1949–2021

Abstract

Tropical cyclones (TCs) are extreme meteorological phenomena, characterized by intense winds and torrential rainfall, which pose severe risks to coastal inhabitants and infrastructure. In the South China Sea (SCS), TCs predominantly form during the main season from May to October. A comprehensive analysis of TC genesis within the SCS during May–September from 1949 to 2021 reveals a significant upward trend in TC frequency. To elucidate the underlying mechanisms driving this trend, we conducted diagnostic analyses of the Genesis Potential Index (GPI) and examined variations in relative humidity (RH) and specific humidity (SH). Our results demonstrate that anomalously elevated mid-level RH is the primary driver of the increasing frequency of locally generated SCS TCs, with this rise in RH attributed to changes in SH primarily influenced by vertical advection processes. These advection processes are largely facilitated by Ekman pumping, driven by the warming of sea surface temperatures (SST) in the SCS. This study establishes a robust linkage between the increasing TC frequency and the warming SST trend in the SCS, underscoring the profound influence of regional climate change on TC activity in the region.