The interactions between the summer urban heat islands and heatwaves in Beijing: from past to future

The coexistence of urban heat islands (UHIs) and heatwaves (HWs) enhances the stress on human society. However, how UHIs responds to the HWs and the interaction mechanisms between the UHIs and HWs in historical period and under different global warming levels (GWL) 1.5 ºC and 2 ºC scenarios are still elusive. In this study, the regional climate model ALARO-SURFEX (incorporated with LCZs) will be firstly used to estimate the historical interactions between the UHI and HW and the contribution of urbanization to the HWs in Beijing. The intensifying impact of three HWs (daytime HW, nighttime HWs, compound HW) on the UHI will be analyzed, and its energy mechanism will also be revealed. Secondly, the ensembled EAS-CORDEX data calibrated by adding hourly urban signatures will be used to force the offline SURFEX model to project the future urban climate in Beijing. The HW duration, frequency, and intensity will be estimated, and the UHI intensity and pattern will be investigated before, during, and after three kinds of HWs under different warming levels (GWL1.5 and GWL2). Understanding the interaction mechanisms of HWs and UHIs, as well as projecting for HWs and UHIs under the Paris Agreement, would be beneficial for stakeholders and city planners in developing future local adaptation policies.