Spatio-Temporal Characteristics of Rainfall over Complex Terrain in the Middle Reaches of the Yangtze River Basin during the Warm Seasons of 2016-2020

Based on the hourly rain gauge data from the China Meteorological Administration during May-September of 2016-2020, we first analyze the spatio-temporal distributions of total rainfall (TR) and short-duration heavy rainfall (SDHR, ≥20 mm h^-1) over the middle reaches of the Yangtze River basin. We then conduct the diurnal variations of TR, SDHR and the contribution of SDHR to TR (CST) over three types of terrain (i.e., mountain, foothill and plain). The main results are as follows. For all three types of terrains, the amount of TR and SDHR both maximized in June/July, and the CSTs (both in amount and frequency) peaked in August. Foothill rainfall is characterized by a high TR amount and a large CST (in amount); mountain rainfall is characterized by a high TR frequency but a small CST (in amount); and plain rainfall shows a low TR amount and frequency, but a large CST (in amount). Overall, the stations with a large TR are mainly located in the mountains and foothills, while the stations with a large SDHR are mainly concentrated in the foothills and plains that are close to the mountainous areas. For all three types of terrains, the diurnal variations of both TR and SDHR exhibit a double-peak (in the early morning and in the late afternoon). Around the later peak, the amount and frequency of the SDHR in the foothills is larger than those of mountains and plains. From midnight to afternoon, the TR amount in the foothills increase significantly, suggesting that thermal instability may play an important role in this process. From May to August, rainfall in three types of terrains all experience a significant phase shift from the early-morning peak to the late-afternoon peak.