ＴＭの熱赤外データとＡＭｅＤＡＳの気温データを利用した東京圏のヒートアイランドの広域化の解析

Abstract

The relationship between temperature changes and the expansion of Tokyo Metropolitan Area was studied using multi-temporal Landsat Thematic Mapper (TM) satellite images. The correlation between the ratio of green covering and brightness temperature was assumed to be an index of urbanization, thus, the relation between the ratio of green covering and air temperature in different seasons was verified around the Automated Meteorological Data Acquisition System (AMeDAS) observation point in Tokyo Metropolitan Area. The area located in NDVI >0.1 was assumed to be a vegetation region, on the other hand, the vegetation in the concentric circle of 0.6 km from the point where AMeDAS was observed, had been extracted from multitemporal TM data.The interrelationships between vegetated area and air temperature in Tokyo metropolis were established by comparing the daily average maximum temperature (Tmax), the daily average minimum temperature (Tmin) the average temperature at 9 p.m. (T21), during winter, summer and autumn using TM images and AMeDAS data. As a result, the strong correlation between a green covering and the daily minimum temperature was revealed at each season. In contrast, such a relation was not observed between the ratio of green covering and the maximum temperature.The variation of brightness temperature of the Tokyo area was estimated using thermal infrared data of TM band 6. Because the DN value changes with the state of performance degradation of the sensor or the atmosphere interface, the absolute value of derived temperature can not be compared to the heat island phenomena. Therefore, the relative change of DN value of thermal infrared data was ideal for studying the heat island phenomena. DN values were extracted from 2 Landsat TM night images acquired on August 1984 and August 1994, which had been used to estimate the expansion of the heat island phenomena.Relative Warming Index (RWI) of the AMeDAS observation point was also evaluated from the rate of change (19841994) of the daily minimum temperature of Tokyo (Otemachi). The rate of change of RWI corresponded to the distribution of differences in brightness temperature around Tokyo. The spatial analysis of relative warming index (RWI) for the 10 years of observations suggests that the warming rate of suburban area was much more pronounced than that of central Tokyo, and the rural side of the suburban area recorded a relatively low RWI than that of the same facing towards central Tokyo. The results from satellite images show of consistency with meteorological records.