Influence of Feedbacks in the Climate–Energetics System on the Intensity of an Urban Heat Island

Resumo

Both horizontal and vertical heat exchanges and feedbacks between air temperature and anthropogenic heat fluxes significantly affect the characteristics of the urban heat island (UHI). The UHI intensity depends, in particular, on the ratio between the scales L_A (area of anthropogenic forcing) and L_γ (distance passed by an air particle of the oncoming stably stratified flow before its temperature approaches air temperature within the UHI). Both advection and feedback effects may be estimated based on the equation for the local heat balance of the underlying surface. In this case, heat advection is taken into account by calculating temperatures individually for the atmospheric boundary layer and the surface of the urban canopy layer. The estimates show that the asymptotics of strong advection is more characteristic of a typical city. However, under weak winds, with consideration for the feedback between air temperature and anthropogenic heat flux, some deviations from this asymptotics are probable.