Characteristics and Evolution of Precipitation in Tropical Cyclones Landing in China over the Past 43 Years

Based on ERA5 reanalysis data, this study investigates the precipitation distribution and its changes in tropical cyclones (TCs) that landed in China over the past 43 years (1980-2022), considering satellite data assimilation. It also examines meteorological elements influencing TC precipitation, including 200hPa geopotential height, 500hPa geopotential height, 850hPa wind field, and 500hPa relative humidity, as well as the precipitation during the landing period of TCs. Using the unsupervised machine learning method of Self-Organizing Maps, the study classifies precipitation in 449 landing TCs.
Results reveal four main types of precipitation distributions in TCs landing in China: I - Northeastern Distribution, II - Concentrated Precipitation, III - Southern Extension, and IV - Southern Intensification. Type I, accounting for 6.2% of the TCs, typically occurs when the South Asian High overlaps with the Western Pacific Subtropical High to the southeast of the TC, and the influence of the westerly trough is significant, leading to a northeastward “6” shaped precipitation distribution with the largest area of light rain and the intense precipitation center in the northeast quadrant of the TC. Type II, most common in autumn and representing 26.5% of the TCs, occurs under the joint influence of maritime and continental block highs, resulting in the smallest precipitation area with the weakest average intensity, symmetrically distributed around the TC center. Type III, the primary precipitation pattern in 33% of the TCs, is characterized by the strongest South Asian High with the TC located at the outflow of the high and influenced by the strong low-level southwest monsoon, resulting in a larger precipitation area in the southern part of the TC and an asymmetric comma-shaped total precipitation distribution, with intense precipitation in the southern quadrant. Type IV, accounting for the highest proportion of 34%, is distinguished by a broad influence of the southwestern airflow, with the Western Pacific belt-like subtropical high and the southwestern jet stream jointly transporting warm and moist air, leading to the strongest average precipitation in TCs, the largest area of intense inner-core precipitation located southwest of the TC center, and peripheral precipitation mainly in the southeastern and southwestern quadrants, displaying a distinct asymmetric distribution.

Among these four types, the number of Type III - South Asian High Southern Extension TCs has significantly increased in the past decade, which is related to the warming of the Tibetan Plateau under the global warming context. This indicates the need for enhanced attention to TCs and their southern regions in future forecasts and disaster prevention of TC-landing precipitation.