Heavy Precipitation Trends and Regional Disparities in South China During the Pre-flood Period of 1965–2016

Based on daily precipitation data from 192 observation stations in South China during the pre-flood period (April–June) from 1965 to 2016, this study analyzed the spatiotemporal variations of the heavy precipitation concentration index (Q index). The results showed that the intensity of heavy precipitation exhibited an increasing trend across most regions of South China. The multi-year mean Q index for the stations ranged from 0.3 to 0.6, with an overall average of 0.375. Notably, significant upward trends in both the heavy precipitation and Q index were observed in the inland and western mountainous areas of South China, indicating a higher flood risk in these regions. Moreover, an analysis of precipitation duration showed that 2-day heavy rainfall events are increasing in the inland areas, western mountains, and eastern Guangdong, while 3-day and 4-day heavy rainfall events steadily increased primarily in coastal areas, with 3-day events also increasing in eastern Guangzhou. The observed rise of heavy precipitation during the pre-flood period across the western mountainous areas, eastern Guangdong, and southeastern coastal areas of South China is mainly attributed to an increase in long-duration heavy precipitation.