Urbanization effects on intensifying extreme precipitation in the rapidly urbanized Tai Lake Plain in East China

Extreme precipitation (EP) exerts various effects on human life and ecosystems with global warming and regional urbanization. However, the specific contribution of accelerating urbani-zation to EP changes is less understood. Taking the Tai Lake Plain (TLP) (among the top three most urbanized regions in China) as the study area, this study identified EP changes in frequency and magnitude using Innovative Trend Analysis (ITA), and quantified urbanization impacts on EP innovatively using a dynamical approach for classifying urban and rural stations based on time -varying land use. The results indicated that: (1) From 1966 to 2015, EP is becoming increasingly frequent, intense and persistent, particularly in the northeast and southeast of TLP. Much attention should be paid to the higher risks of flooding or waterlogging especially in big cities (e. g., Shanghai and Hangzhou) in these areas; (2) It was estimated that urbanization induced an average increase of 0.16 days per decade to EP frequency, contributing about 20% to the pro-longing trend. Meanwhile, approximately 15% of the intensifying trend for magnitude was attributed to urbanization, i.e., 3.61 units per decade on average; (3) Up to half of the increases of EP risks were attributed to rapid urbanization during 1966-2015, as denoted by positive fraction values (i.e., 0.12-0.52) of attributable risk. Such results reveal the multi-faceted behaviors of EP in relation to time-varying urbanization in TLP region for the first time. They could provide valuable insights in planning urban landscape and mitigating adverse impacts of extreme climate activities at the local scale.

Automated summary

With global warming and regional urbanization, extreme precipitation (EP) has various effects on human life and ecosystems. However, the specific contribution of accelerating urbanization to EP changes is less understood. This study focused on the Tai Lake Plain (TLP), one of the most urbanized regions in China, and found that EP is becoming more frequent and intense, particularly in the northeast and southeast of TLP. Urbanization has contributed to the increase in EP frequency and magnitude, accounting for a significant portion of the overall trend.