Long-term surface wind changes in the Tokyo metropolitan area in the afternoon of sunny days in the warm season

The urban heat-island effect of the Tokyo metropolitan area is believed to cause widespread warming in the daytime of the warm season, resulting in intensified convergence over the central Kanto plain. In order to detect this change, a comparative analysis of surface wind fields was made for the periods 19231928 and 1991-2001 for sunny days (at least 8 hours' sunshine) from May to August. It was found that the magnitude of daytime pressure fall (at 1400 LT relative to 0600 and 2200 LT) had increased by 0.2-0.3 hPa in the central and northwestern part of the plain, with a slight change in surface winds in such a way as to converge toward the central Kanto plain.