Effect of urban block geometry on surface wind and air temperature over a sandbank in the central area of Osaka city, Japan

– To investigate the influence of urban block geometries on wind and air temperature in a sandbank area in mid-summer, high-resolution analyses were conducted using a meteorological model. Low building density contributes to the ventilation of the study area. The large sky view factor decreases the air temperature at night, while increasing surface temperatures on the ground and buildings in the daytime. However, the air temperature in the daytime is not significantly influenced because the sensible heat from urban surfaces is diluted in a mixed layer, with significant ventilation partly suppressing the air temperature increase. Therefore, the influence of urban block geometry on air temperature is considerably lower than that on the wind. The influence of rivers on the ventilation in the sandbank is much less than that of the urban block geometries. The cooling effect of the rivers in the daytime is comparable to the change in radiative cooling caused by sparse urban blocks.