The Surface Urban Energy and Water Balance Scheme (SUEWS): Evaluation in Los Angeles and Vancouver

Water and energy exchanges have been severely impacted by anthropogenic behavior and land cover changes. These alterations in land cover have led to increased surface runoff, reduced evaporation, and elevated sensible heat emissions to the urban boundary layer. Despite possible consequences of flooding, mixing of the boundary layer, and pollutant dispersion, water and energy balance fluxes are rarely measured. This paper presents an urban water and energy balance model that requires minimal input data which can be acquired from standard meteorological stations or a meso-scale model. The authors combined previously published models with novel parameterizations to establish the Surface Urban Energy and Water Balance Scheme (SUEWS), which allowed them to calculate energy and water balances at the neighborhood scale. The rate of evaporation-interception for a single layer with multiple surface types was analyzed and the horizontal water movements at the surface and in the soil were incorporated to reduce the number of required input variables and to achieve a more comprehensive scope of the water and energy exchange processes. SUEWS was evaluated against measured net-all wave radiation and turbulent fluxes of sensible and latent heat from Los Angeles, California, and Vancouver, Canada. The results demonstrated that SUEWS was able to accurately simulate the net all-wave radiation along with turbulent sensible and latent heat fluxes. The model also sufficiently tracked observed soil moisture deficit and surface wetness state in addition to responding effectively to short-term events and seasonal variations of vegetation. Based on this research, the intelligible SUEWS model can be readily applied when determining the components of urban surface cover, making planning decisions related to water conservation and restrictions, and when investigating climate mitigation strategies where it is a necessity for implications of heat and water to be considered.