Abstract
On a building rooftop in central Tokyo, test plots of Carex thunbergii Steud. (hygrophyte plot) and Zoysia japonica Steud. (turf plot) were prepared to evaluate heat budget characteristics and effects on controlling rising temperatures. Results show that both the hygrophyte and turf plots' rooftop surface average temperatures were lower than mean temperatures in sunny summer weather, with only slight generation of heat flux on the rooftop surface. Furthermore, a tendency was noted whereby the rooftop surface of hygrophyte plot was 0.5-0.7°C cooler than the turf plot. In the hygrophyte plot, the temperature in the community was lower than the outside temperature: latent heat was reduced by evapotranspiration and the sunlight was blocked by above ground part of Carex thunbergii. The low temperature in the hygrophyte community also affected the upper part of the community, suggesting easing of the heat island effect in the form not only of temperature rise control of the rooftop but also upper part cooling. The hygrophyte plot showed much emergence of latent heat. The period of sensible heat with the quantity of heat storage of the vegetation base-a negative value-increased. It also showed a result supporting a cooling effect from the heat budget.
