Abstract
The surface heat island and the consequent wind system around Tokyo are investigated on the basis of weekday-weekend differences of air temperature and wind vector. By using data covering a nine-year period, temperature and wind fields on weekend days are expressed in the form of departure from those on weekdays. The result reveals the existence of a cool island (i.e. area with lower temperature than on weekdays) centered on the city from Saturday night to Sunday night. The temperature drop at the center of the city is 0.2-0.3°C.In the daytime on Sundays, the cool island covers most of the area within a radius of 50km from the center and is accompanied by divergent wind (i.e. smaller convergence than on weekdays) with order of 0.1ms-1. The divergent wind is detectable under mean wind of 1.5-3ms-1 as well as in near-calm cases.
The existence of divergent wind accompanying a cool island on Sundays is detected also for the area around Osaka.
