1990 Volume 63 Issue 1 Pages 98-107
This paper describes the urban climate in Tokyo phenomenally from the viewpoint of regional geography. Climatic elements discussed here are temperature, precipitation, humidity and solar radiation. There are previous studies, written in English, such as those by YOSHINO (1981), KAWAMURA (1985) and YAMASHITA (1988), and so this paper is generally intended to deal with others than those noted in the above-mentioned three papers.
Secular changes of seasonal variations of air temperature are shown at first. Next, Tokyo's heat island intensity is shown diurnally and seasonally as an isopleth. Using Fuchu and Koshigaya as the rural control sites for Tokyo, heat island intensity and its diurnal frequency distribution are obtained by the temperature differences with Tokyo. Its behavior is also explained by the difference of wind direction and speed.
Annual variation of precipitation is shown since the beginning of the observation. Moreover, the change of days is shown with ranked precipitation amounts as follows: 0.0 mm, 0.1-1.0 mm, 1.1-9.9 mm, 10.0 mm and over. Effects of a city on precipitation are not so simple because the number of convective rain days with 31 mm and over is very variable dependent on the atmospheric conditions of the period.
Humidity has decreased very drastically for the last two decades. Reduction index of insolation in Tokyo is shown as monthly variations, and this is a very good indicator for total air pollution. Judging from tendency of this indicator, air pollution condition in Tokyo is not always improved in these days.