In summer, weather in urban areas of the south-east region of Japan is humid and hot. It seems that the heat-island effect in urban areas on human life is greatest at night during summer, because hot and humid weather inhibits sleep thereby leading to poor health. A prediction model for urban air temperatures is needed in order to develop countermeasures for thermal environmental problems.

The estimation of air temperature within the constant flux layer is based on a one-dimensional heat balance. Further, using the Monin-Obuklov length, momentum, heat and moisture fluxes are calculated to account for atmospheric stabilities. This paper discusses a study of the influence of atmospheric stabilities on the formation of night temperature within the basic concept of a ‘heat transfer coefficient of the surface boundary layer’.

The results clearly indicated that the greatest causes of the increase of night temperatures in urban areas are the release of artificial heat and heat storage in soil. In conclusion, from the results of this investigation, a concept of the required green-area ratio needed to control urban night temperatures is proposed.