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A direct comparison of urban and rural surface energy balances is conducted for the Beijing metropolitan area,in addition to analyses of various datasets for the sake of insights into the observed urban-rural contrasts.The results indicate that,overall,the inner-city (urban) area receives a lower amount of the incoming shortwave radiation but a higher amount of the incoming longwave radiation.Such a contrast is attributable not only to differences in the aerosol optical depth,but to differences in the cloud fractions.The combined effects of the metropolitan aerosol load and cloud characteristics are found to account for a large part of the urban-rural differences in the incoming shortwave radiation.Moreover,the urban-rural differences in the incoming longwave radiation are unlikely to result from the presence of more abundant greenhouse gasesover urban areas,because the rural atmosphere is found to contain a higher amount of moisture.The higher incoming longwave radiation over the urban areas is mostly possibly due to the higher air temperature,characteristically,over the inner-city area (i.e.,a common outcome of the urban heat island effect).A comparison of turbulent energy fluxes over urban and rural areas indicates that urban areas are characterized by higher sensible heat fluxes and lower latent heat fluxes.The relative discrepancies in the magnitude between the sensible heat and latent heat fluxes see evident intraannualvariations and are typically larger in the boreal summer than in the winter.The intraannual variations in the urban-rural contrast in evapotranspiration (ET) suggest that the difference in evapotranspiration is due not only to the difference in the fractional vegetation,but to the difference in soil water availability.Furthermore,the urban areas are provided with a higher amount of the available energy (namely the sum of sensible heat and latent heat fluxes) than the rural areas,except in May and October when evapotranspiration in the rural areas greatly exceeds that in the urban areas.This study provides useful observational evidence that urban-rural contrasts in surface energy balance stem from the corresponding discrepancies in atmospheric and land-surface conditions.More accurate numerical representations of urban terrain which include sufficiently complete urban hydrological and micrometeorological processes are strongly needed.