Water and Heat Balances for Urban Surfaces

Abstract: Water and heat flows for three different types of surfacefound within Stockholm, Sweden, were simulated with asoil-vegetation-atmosphere transfer (SVAT) model. Theinfiltration process of a till soil was investigated toestimate the importance of preferential water flow. Theseasonal pattern of soil moisture content could be simulatedwithout taking preferential flow into consideration. However,specific infiltration events showed clear indications ofpreferential flow. The surface heat fluxes of a paved roadcould be simulated reliably with model parameterisation basedon independent information. The impact of the urban modifiedclimate on evapotranspiration (ET) from vegetated surfaces wassimulated by making changes to the meteorological forcing inthe form of increased long-wave radiation and enhancednocturnal air temperature. Long-wave radiation had the mostinfluence on ET, enhancing transpiration from low vegetationand soil evaporation, whereas air temperature mainly increasedtranspiration from tall vegetation. The results are useful forparameterisation of distributed hydrological and meteorologicalmodels.