Using High-resolution Satellite Precipitation Products to Explore the Effect of Urbanization on Heavy Rainfall over Yangtze River Delta of China

Abstract:

Extreme precipitation events (EPEs) in the urban agglomeration areas often cause flooding and result in the loss of life and property. In this study, three high spatial-temporal resolution precipitation products were used to analyzed warm season (May-October) hourly EPEs over the Yangtze River Delta (YRD) and the possible link between EPEs and environmental factors (such as urbanization, climate change, and orography). The zonal movement feature of hourly precipitation are analyzed using Hovmoller diagrams, the results showed that the eastward propagating precipitation systems created an intensive rainfall center in the southwest mountainous of YRD due to orographic lifting, while the occurrence of precipitation was decreased in the leeward side of the mountain (118°E-119°E). However, the propagating precipitation systems were enchanted in the plains where the urban located. According to the analysis of extreme rainfall (exceeding 95^th percentile), we found that the higher extreme rainfall mainly intensified over city clusters (especially in Nanjing, Changzhou, and Nantong cities). Also, such is more pronounced during strong-NESO years. This result indicated that urbanization substantially contributed to the increase in both amounts and frequency of EPEs in the YRD, although the rainfall was largely controlled by synoptic or large-scale weather systems. In addition, the change of extreme rainfall was investigated by the generalized additive model for location, scale, and shape (GAMLSS) model, indicating the change of extreme rainfall in the urban regions is more obvious under the nonstationary scenario.