The study of the changes in precipitation induced by intensified urbanization and climate change by observational records

Both climate change and intensified urban development will affect the temporal and spatial distribution of rainfall. There is still a lack of relatively quantitative and comparative studies. Most cities in China entered the rapid urbanization stage around 2000. This study focuses on the megacities Beijing, Shenzhen and Hong Kong. Based on rainfall observation data and land use and other remote sensing image data, this study investigates the impacts of the impervious areas on the temporal and spatial changes of short-duration and long-duration heavy rainfall before and after rapid urbanization. The impact of climate change on rainfall intensity is also analyzed. The results show that there are huge spatial shifts in rainfall after rapid urbanization. For example, it is observed that the center of the heavy rainfall shifts from northeast to southwest, and the hydrological homogenous areas in Beijing have increased from two to three after rapid urbanization. Meanwhile, with the influence of climate change, the intensity of rainfall is increasing, but due to urbanization, the increase varies greatly in each hydrological homogenous area. Shenzhen and Hongkong, the neighbor cities without physical boundaries, have entered into different urbanization stages since 1990. Hong Kong has developed very slowly, while Shenzhen has developed very rapidly. As a result, the short-duration heavy rainfall is mainly concentrated in Shenzhen, and the long-duration heavy rainfall is mainly concentrated in Hongkong. The short-duration heavy rainfall in Shenzhen mostly occurs at noon, while that in Hong Kong mostly occurs in the morning. The urbanizations of Hong Kong and Shenzhen are different, which resulted in different impacts on rainfall in these two cities. This study examines the impact mechanisms of urbanization and climate change on rainfall in cities in different climate zones. It provides scientific basis in supporting the city planning and the development of resilient cities.