Urbanization influences hydrologic cycle significantly on local,regional even global scale.With urbanization the water resources demand for dense population sharpened,thus it is a great challenge to ensure water suppl...Urbanization influences hydrologic cycle significantly on local,regional even global scale.With urbanization the water resources demand for dense population sharpened,thus it is a great challenge to ensure water supply for some metropolises such as Beijing.Urban area is traditionally considered as the area with lower evapotranspiration(ET) on account of the impervious surface and the lower wind speed.For most remote sensing models,the ET,defined as latent heat in energy budget,is estimated as the difference between net radiation and sensible heat.The sensible heat is generally higher in urban area due to the high surface temperature caused by heat island,therefore the latent heat(i.e.the ET) in urban area is lower than that in other region.We estimated water consumption from 2003 to 2012 in Beijing based on water balance method and found that the annual mean ET in urban area was about 654 mm.However,using Surface Energy Balance System(SEBS) model,the annual mean ET in urban area was only 348 mm.We attributed this inconsistence to the impact of anthropogenic heat and quantified this impact on the basis of the night-light maps.Therefore,a new model SEBS-Urban,coupling SEBS model and anthropogenic heat was developed to estimate the ET in urban area.The ET in urban area of Beijing estimated by SEBS-Urban showed a good agreement with the ET from water balance method.The findings from this study highlighted that anthropogenic heat should be included in the surface energy budget for a highly urbanized area.展开更多
Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quanti...Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management.Through the integration of "spatial structure theory" in urban geography and "surface energy balance" in urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components(e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components.The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos. 51479088,41630856 & 51279208)
文摘Urbanization influences hydrologic cycle significantly on local,regional even global scale.With urbanization the water resources demand for dense population sharpened,thus it is a great challenge to ensure water supply for some metropolises such as Beijing.Urban area is traditionally considered as the area with lower evapotranspiration(ET) on account of the impervious surface and the lower wind speed.For most remote sensing models,the ET,defined as latent heat in energy budget,is estimated as the difference between net radiation and sensible heat.The sensible heat is generally higher in urban area due to the high surface temperature caused by heat island,therefore the latent heat(i.e.the ET) in urban area is lower than that in other region.We estimated water consumption from 2003 to 2012 in Beijing based on water balance method and found that the annual mean ET in urban area was about 654 mm.However,using Surface Energy Balance System(SEBS) model,the annual mean ET in urban area was only 348 mm.We attributed this inconsistence to the impact of anthropogenic heat and quantified this impact on the basis of the night-light maps.Therefore,a new model SEBS-Urban,coupling SEBS model and anthropogenic heat was developed to estimate the ET in urban area.The ET in urban area of Beijing estimated by SEBS-Urban showed a good agreement with the ET from water balance method.The findings from this study highlighted that anthropogenic heat should be included in the surface energy budget for a highly urbanized area.
基金financially supported by the Major Projects of the National Natural Science Foundation of China (Grant No. 41590842)General Program of the National Natural Science Foundation of China (Grant No. 41371408)
文摘Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management.Through the integration of "spatial structure theory" in urban geography and "surface energy balance" in urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components(e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components.The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.
