Environmental Impact of Urban Heat Island Phenomena —Cause-effect chain and evaluation in Osaka City—

Abstract

The impacts of urban heat island phenomenon on human activity and ecosystems have already been obvious in Japanese large cities. To discuss importance of urban heat island mitigation measures, it is necessary to identify and quantify urban heat island impacts such as change in energy use (cooling, heating and hot water supply), change in water use, heat stress, damage to urban ecosystem, air pollution, change in precipitation and floods, etc. In this paper, cause-effect chain of urban heat island impacts is proposed and some examples of heat island impacts in Osaka city are identified and evaluated. Change in energy consumption in residential and commercial sector is evaluated quantitatively by numerical simulation. The result shows the difference in total energy consumption by different air temperature is small since decrease in heating and hot water energy use compensate for increase in cooling energy use.