Evaluating the impacts of land use/land cover changes and climate variations on urban heat islands using the WRF-UCM model in Hefei, China

The urban heat island (UHI) phenomenon is concurrently influenced by urban expansion and climate change. However, the individual impacts of land use/land cover (LULC) changes and climate change remain unclear. In the present study, a high-resolution numerical Weather Research and Forecasting (WRF) model coupled with a single-layer urban canopy model (UCM) is implemented for Hefei to assess the influences of LULC and climate change simultaneously. The comprehensive increase in UHI intensity (UHII) was 0.76 K from 2003 to 2019 in the study area. The overall influence of LULC changes on the UHI effect was a 0.33 K increase in intensity and a 190 km² expansion in coverage. The results also show that the emergence of new high-intensity urban areas developed from farmlands had the strongest impact on UHI development compared to other types of LULC changes. The overall contribution of climate change to the UHII increased by 0.27 K from 2003 to 2019. The change in the storage heat flux was found to be responsible for the nocturnal UHII variation and long-term increase in the UHII, while the sensible heat flux was responsible for the diurnal UHII.