Characterizing the seasonal relationships between urban heat island and surface energy balance fluxes considering the impact of three-dimensional urban morphology

Abstract

Urbanization has disrupted the energy balance of natural surfaces, leading to the formation and intensification of urban heat island (UHI) phenomenon. Current research on the relationship between surface energy balance (SEB) and UHI mainly focuses on either a macro perspective of large-scale regions or a micro perspective based on numerical microclimate simulations. However, there are still relatively few studies conducted on the local scale of cities. Here, we investigated the relationships between seasonal SEB and land surface temperature (LST) based on local climate zones (LCZ) and explored the impact of three-dimensional (3D) urban morphology on SEB. Our results revealed that: (1) urban building spaces have relatively higher LST, sensible heat flux, and storage heat flux, but lower net radiation and latent heat flux, compared to urban blue and green spaces; (2) among LCZ built types, the compact and large low-rise buildings have high LST and heat-inducing energy fluxes, while the compact and open high-rise buildings exhibit the opposite situation; (3) the component proportions of SEB fluxes exhibit a more significant linear correlation with UHI intensity compared to the relative differences between SEB fluxes; and (4) 3D building morphology has a higher relative importance in influencing the variations of surface energy balance ratio (SEBR) components than 3D vegetation morphology. Specifically, building height has the greatest impact on the seasonal variations of SEBR components, while the 3D urban greening ratio has relatively high importance among vegetation morphology. These findings enable us to better consider local UHI effect from the perspective of SEB.