Impacts of Long-Term Urbanization on Summer Rainfall Climatology in Yangtze River Delta Agglomeration of China

In this study, we investigated the urbanization-induced summer rainfall changes in the Yangtze River Delta (YRD) by analyzing long-term observations and numerical simulations. The observation-based analysis showed that long-term urbanization increased the region's summer rainfall, particularly through the intensification of heavy rainfall, which is noted as the urban rain island (URI) effect. A series of numerical sensitivity experiments with three historical land use and land cover scenarios (1990, 2000, and 2010) were designed to further understand the urbanization impacts on rainfall. The observed URI effect was well reproduced by the numerical simulations, and on average, urban expansion during 1990-2010 increased summer rainfall over urban areas by 51.91 mm. The URI effect slightly weakened in the late stage of urbanization (2000-2010) compared to the early stage (1990-2000). We conclude that the strengthening of precipitation-inhibiting effects during the late period offset the precipitation-enhancing effects, which led to the weakening of the URI effect.

Automated summary

This study investigates the impact of urbanization on summer rainfall in the Yangtze River Delta using long-term observations and numerical simulations. The study finds that urbanization has led to increased summer rainfall in the region, particularly through the intensification of heavy rainfall events. The numerical simulations reproduce the observed urban rain island effect and show that urban expansion has increased summer rainfall over urban areas by an average of 51.91 mm. However, the urban rain island effect weakens in the later stages of urbanization, potentially due to the strengthening of precipitation-inhibiting effects.