RELATION BETWEEN THE AIR TEMPERATURE DISTRIBUTION AND TEH DENSITY OF HOUSES IN SMALL CITIES IN JAPAN

Abstract

Temperature observations were done at Ogaki city (pop. 75, 000) in Nobi Plain in Central Honshu and at Kumagaya city (pop. 94, 000) in Kanto Plain. Both of them are located in the middle of the flat alluvial plains and surrounded by extensive paddies. The greater parts of their built-up areas are occuppied by one or two story wooden houses. There are only a few tall concrete buildings in their central areas. Their main roads are paved with asphalt and concrete. Typical distribution patterns of city temperature were observed as were shown in the following figures. The observation were done using the elctric thermometers of thermistor type which we made. The thermometers was mounted on the front bumper of an automobile at about two meters above the ground. Several hundreds observations were made using a technique of moving observation at both cities. At the same times, about ten quick-winding thermographs of our types were installed in and around cities. Fig. 4 shows an isopleth of the temperature variation in thirty minuites intervals at a calm day in Ogaki. The densely populated areas show small variations and the changes occur a little later than the countrysides. Figs. 1, 2, and 3 show typical distribution patterns of temperature in Ogaki at different weather conditions. The pattern of the isotherm distribution shows a strong similarity with the distribution of house density in the city as is shown in fig. 1; Higher temperatures were observed at densely built-up areas, and big temperature-gradients were recognized at the surroundings of the cities. Also temperatures on paved roads seemed to be warmer than those on unpaved roads. Relations between temperature distribution and house density of 200 m square were analyzed on both cities, We could find that 10% increase in house density corresponded to 0.2-0.3°C temperature increase as were shown in Fig. 5. However, the -areas covered by two story houses had 0.2-0.4°C higher temperatures than other areas. These values seemed to be effected by weather conditions remarkably, especially by wind speed. When wind is strong, the values of temperature increase decreases strongly.