Changes in population exposure to extreme precipitation in the Yangtze River Delta, China

Precipitation extremes are expected to increase in a warming world, which could have substantial impacts on the environment, social property, and human health, especially in densely populated regions. In this study, the Yangtze River Delta (YRD) was used as a case study to investigate the spatiotemporal characteristics of daily, daytime, and nighttime extreme precipitation events (EPEs), and the population exposure to EPEs based on observational precipitation and population data. The EPEs both in days (duration) and amount (magnitude) showed obvious south-north gradients, with high values occurring in the south and low values in the north. A few stations in the northern parts of the YRD showed weak decreasing trends in extreme precipitation days and amounts during 1961–2018, whereas most of the stations showed positive trends. The stations with significantly increasing trends were mainly located in the central and eastern parts of the YRD. All the EPE indices for the whole area showed increasing trends during 1961–2018. Population exposure to daily, daytime, and nighttime extreme precipitation days (amounts) increased by 37% (40%), 34% (39%), and 41% (41%), respectively, from the early period (1984–1993) to the later period (2009–2018). The significant increase in total exposure to EPEs was dominated by the effect of rapid population growth during 1984–2018. An atmospheric circulation analysis of the EPEs in 2016 showed that the anomalously strong warm and wet southwesterly water–vapor transport from April to October (except for August) on the northwest side of the West Pacific subtropical high merged with cold air, resulting in abnormally more EPEs and exposure in 2016 than any other years of the study period in the YRD. The findings provide information useful to adaptation and mitigation policymaking for regions with conditions similar to the YRD.

Abstract licence: CC BY-NC

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