Quantitatively evaluating the effect of urbanization on heat waves in China

In this study, the long-term trends and spatial characteristics of heat waves (HW) were analyzed using observations at a dense network of 2000 meteorological stations in China during 1961-2014. The contribution of urbanization to HW was quantitatively evaluated at the national scale based on a method of dynamically classifying urban and rural stations. The results based on different HW measures showed that HW in China became increasingly frequent, intense and longer, and emerged earlier and terminated later. More significant variation trends of HW were observed in southern and northern China, whereas relatively weaker and negative trends occurred in the Jianghuai-Plain region. The effect of urbanization on HW was evaluated in eight subregions of China, the results showed that the urbanization had an notable impact on the progression of HW. The urbanization contribution was pronounced in all subregions, especially in the southwestern, northern and southern China, where contributions were found to be >45%. In northwestern China, a negative urbanization effect was found in some HW measures, which was inferred to be related to the local dry climate. Overall, the contribution of urbanization to HW reached 30-50% for the urban areas of China. This study provided great insights in understanding the variations in extreme weather events and their relationships with urbanization.