Composite analysis of the rainfall distribution caused by strong and weak landfalling tropical cyclones over the China Mainland

Abstract

Tropical cyclones (TCs) making landfall in China from 2008 to 2016 were grouped into three clusters based on landfall location and movement. The first two clusters made landfall in Southeast China (SEC), moving either northward or westward/northwestward, while the third cluster made landfall in Southern China (SC) and moved westward or northwestward. A statistical analysis examined differences in precipitation distribution and influencing factors. This analysis utilized data from the China Meteorological Administration (CMA) tropical cyclone database, ECMWF ERA-Interim reanalysis data, and CMORPH (Climate Prediction Center Morphing Technique) precipitation data, derived from both station observations and satellite retrievals. The findings reveal significant differences between strong (more intense than a tropical storm) and weak (less intense than a tropical storm) TCs in different clusters. Strong TCs in first cluster (SEC-strong) cause heavy rainfall areas to shift farther north, particularly in Jiangsu Province, with extreme rainfall occurring in the inner rainbands in a relatively symmetrical pattern. Conversely, rainfall from SEC-weak TCs is markedly asymmetric, concentrated in the inner regions and predominantly to the south of the middle rainbands. For SC-weak TCs, intense precipitation is primarily located in the southwest quadrant. Meanwhile, SC-strong TCs display a broader area of heavy rainfall, with coverage extending further west compared to SC-weak. A dynamic composite analysis of the primary weather systems influencing rainfall distribution before and after landfall was performed for SEC-strong, SEC-weak, SC-strong, and SC-weak TCs. This analysis highlighted significant differences in the positioning of the South Asian High (SAH), the intensity of vertical wind shear (VWS), and the characteristics of moisture convergence zones. Specifically, SEC-strong TCs exhibit a more robust water vapor transport channel, with easterly winds delivering moisture to the northern side of the TC center, compared to SEC-weak. Differences are also evident in their vertical structures, including variations in warm-core intensity, radial vertical motion, the asymmetric distribution of convergence and divergence fields, and instability conditions. Similarly, SC-strong and SC-weak TCs differ in the positioning of the 500 hPa subtropical high and the distribution of integrated atmospheric precipitable water (PW).