Urbanization impacts on sequential flood-heatwave events in the Guangdong-Hong Kong-Macao Greater Bay Area, China

Urbanization has been shown to significantly increase the frequency and intensity of extreme weather events, i.e., extreme precipitation events, and heatwave events. Actually, the occurrence of compound extreme events, such as sequential flood-heatwave (SFH) events, can lead to more severe impacts than singular extreme events. However, the impact of urbanization on these compound extreme events is not well understood. In this study, we examine urbanization effects on the change of SFH events during 1961-2017 in the Guangdong-Hong Kong-Macao Greater Bay Area, China. The results showed that the frequency of SFH events in urban areas increased from 0.218 events per year before the 1990s to 1.401 events per year after the 1990s, while the frequency of SFH events in rural areas increased from 0.250 events per year to 0.920 events per year. The urban contribution of 0.131 events per decade also shows that urbanization can significantly promote the occurrence of SFH events. Furthermore, our analysis indicates that urbanization promotes the growth of SFH events mainly by increasing the frequency of heatwave events. These findings highlight the need for further research on the effects of urbanization on compound extreme events and the development of effective management strategies to reduce their risks.