Impacts of land use/ land cover types on interactions between urban heat island effects and heat waves

The urban heat island (UHI) effect is a widespread phenomenon because of increased urbanization, making the urban thermal environment less comfortable. The UHI effect may worsen during heat waves (HWs), with projected increases in extreme climatic events in the future due to global warming. Researchers have revealed interactions between the UHI effect and HWs using weather station data and proposed mitigation schemes at a city scale. However, the UHI effect in urban areas with different land use/land cover (LULC) types should respond differently to HWs, which has drawn little attention. Hence, this study conducted a mobile transect experiment in the subtropical megacity of Shenzhen and obtained high spatial resolution data. The results showed that the UHI effect was significantly amplified during HWs. The UHI intensity (UHII) of the transect increased from 0.56 +/- 0.50 degrees C under non-heat wave (NHW) conditions to 0.68 +/- 0.65 degrees C during HWs. LULC types had a significant influence on this interaction. The UHII in more urbanized areas increased during HWs, whereas less urbanized areas had improved cooling effects. These interactions were more evident at nighttime. Increasing the natural underlying surface coverage mitigated the intensity and warming potential of the UHI effect. With a 10% increase in the natural underlying surface coverage, the nighttime UHII decreased by 0.38 degrees C and 0.39 degrees C during NHWs and HWs, respectively. These cooling effects were attributed to the increased latent heat consumption during HWs by vegetation. Therefore, different measures should be taken in other areas to mitigate UHII amplification during HWs.