Heavier Precipitation in Response to Longer-Lasting Tropical Cyclones and Rapid Urbanization over the Yangtze River Delta of Eastern China

Abstract

Abstract Precipitation induced by tropical cyclones (TCs) over cities is associated with both TC duration and urbanization; however, observational evidence of the impacts of TC duration and urbanization on precipitation in megalopolises is limited. In this study, the Yangtze River Delta (YRD) of eastern China is taken as a typical region because this region has been experiencing both rapid urbanization processes and frequent TC attacks. During 1979–2018, we find reduced translation speed and increased meandering of TCs over the YRD, resulting in increased TC duration and the proportion of TC stalling in this region. The correlation between TC duration and TC-induced precipitation amount is significant across the YRD region but is relatively weak in areas with faster urbanization expansion rates. Long-term increases in TC-induced precipitation are found in both rural and urban areas but are larger for urban areas. Urbanization plays an important role in enhancing TC-induced precipitation over urban areas of the YRD region. Areas with faster urbanization expansion rates and longer TC durations have larger TC-induced precipitation, suggesting that urban expansion and TC duration jointly amplify TC-induced precipitation. Our findings suggest that urban planners, in areas potentially affected by TCs, should consider adaptation measures to mitigate the impacts of urban rainstorms amplified by the combined effects of TCs and urbanization. Significance Statement The combined impacts of tropical cyclone (TC) duration and urbanization on precipitation have received limited attention, especially in populated urban areas. Here, we focus on the Yangtze River Delta (YRD) of eastern China, an urban agglomeration frequently impacted by TCs. We find that slowed translation and increased meandering of TCs have led to longer TC duration and stalling over the 500-km YRD buffer during 1979–2018. Significant positive correlation between TC duration and TC-induced precipitation indicates that longer-lasting TCs trigger greater precipitation. The greater TC-induced precipitation due to increased TC duration is further amplified by urban expansion.