Abstract
High NO2 concentrations at night-time at the Tokyo Tower, located in the center of the Tokyo metropolitan area, for the spring to summer seasons and the autumn to early winter seasons of 2009 were analyzed. High potential ozone (PO) concentrations were observed at night-time during the spring to summer seasons, whereas a uniformly low concentration was observed at night-time during the autumn to early winter seasons. Moreover, the average PO concentrations exceeding 80 ppb on average were necessarily observed during the spring to summer seasons. In these seasons, the day-time average PO concentration on the next day exceeded 80 ppb. One of these three cases shows that a heat low was created in the Yamanashi Prefecture during the day-time and a photochemical smog alert was issued, which is supposed to be the transport of pollution from the Tokyo metropolitan area.
