Heat balance analysis in urban areas by high-resolution satellite remote sensing

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The heat island effect in urban areas is caused by not only anthropologic heat discharge but also heat balance changes as a result of surface land-cover changes. This study developed a new analysis method that enables us to discriminate these two effects and to evaluate them quantitatively. A heat balance model was modified to be able to distinguish the two components ; the anthropologic sensible heat due to anthropologic heat discharge, and the natural sensible heat due to solar and atmospheric radiation. The model calculates surface heat flux components ; net radiation, ground heat flux, sensible heat flux, and latent heat flux, respectively. The sensible heat flux is proportional to a difference of the surface and atmosphere temperatures. We assumed that the anthropologic sensible heat can be given as a difference between the actually measured sensible heat flux and the modeled sensible heat flux from the solar radiation. By using this model, the heat balance in Nagoya was analyzed. Model inputs were of the parameters from high-resolution satellite remote sensing data such as ASTER and Landsat/ETM+, and the meteorological data such as temperature, solar radiation, and wind speed. As a result, we could obtain reasonable heat balance changes that reflect seasonal air-conditioning demands and solar radiation patterns. Moreover, the sensible heat fluxes of the urban areas were always higher than those of the other land-cover types. Consequently, we concluded that our new method allowed us to estimate anthropologic heat discharge in urban areas, and is quite useful to investigate the heat island effect in urban areas.