Relationship between South China Sea summer monsoon onset and landfalling tropical cyclone frequency in China

Between 1979 and 2015, the anticorrelation between the frequency of landfalling tropical cyclones (LTCs) in mainland China from June to October and the South China Sea summer monsoon (SCSSM) onset date can be attributed to variations in the western North Pacific subtropical high (WNPSH) and monsoon trough (MT) that correspond to the SCSSM onset. When the SCSSM onset is early, the WNPSH shrinks northeastwards and the MT becomes increasingly strong and exhibits a northwards shift. These features lead to anomalous lower-level cyclonic circulation around Luzon Island and a mid-tropospheric easterly anomaly over the Chinese coastal regions, which favour the generation of TCs in the western part of the North Pacific that makes landfall on the southeastern coast of China. In contrast, the circulation anomaly prohibits landfalling TCs in mainland China when the SCSSM onset is delayed. The SCSSM onset has the potential to be an indicator of TC landfall frequency in mainland China.