Modeling urban energy balance and temperature differences of different underlying surfaces
城市不同下垫面的能量平衡及温度差异模拟

Urban energy balance is a physical basis of studying urban heat island effect.Underlying surfaces have a significant effect on urban thermal budget.In this study,different types of underlying surface,namely vegetation cover types(forest and grassland),impervious overlay types(roads and houses),and meteorological data measured in Beijing teaching botanical garden in 2010,were used to study urban energy balance and temperature differences of different underlying surfaces with a local-scale urban meteorological parameterization scheme(LUMPS).The results showed that: 1) urban underlying surfaces had a large impact on energy expenditures.Therein,the annual average Bowen ratio of vegetation cover regions was 0.28,while that of impervious layer regions reached 4.60.Moreover,the differences of energy expenditure mainly appeared in the vegetation growing season;2) the common process of urban sprawl was that grassland or forest were replaced by houses and roads.This process was accompanied by the significant changes of energy expenditures,namely the process of sensible heat increased and latent heat decreased.For example,in the process of conversion of vegetation surface to impervious surface,the sensible heat flux increased by 32.74 W/m2,the latent heat flux decreased by 38.87 W/m2,and the surface heat flux increased by 7.95 W/m2;3) corresponding to the differences of latent heat and temperature,the results displayed that the vegetation cover regions had lower temperture than impervious cover regions due to their different specific heat capacity and energy assignment.And only the cooling effect of evapotranspiration could make the air temperature of vegetation cover regions 2.63℃ lower than impervious cover regions in theory.