Structure of the Urban Heat Island in Nagasaki City

In order to study the size and magnitude of the urban heat island in Naga-saki City, surface air temperatures have been measured by a thermocouple mounted on the roof of a car in the early morning before sunrise. Air tempe-ratures over Nagasaki Bay were also measured by the use of a ferryboat. Moreover, the temperatures measured at Koga, where a typical rural region in the vicinity of the urban disrict, were compared with the urban ones. Main results obtained in this study are in the following. (1) The core of the urban heat island is situated in the central duilt-up area of the city (Hamanomachi and Doza-machi), where the mean air temperature is high by 3.4 ℃ compared with Koga. The difference in air temprature between the maximum and the minimum (Nishi-machi) in the urban district is about 3.0 ℃. (2) Air temperstures at a height of 2.5m over Nagasaki Bay is slightly higher than those of coatal region. (3) The observation of vertical air temperature in the urban strict shows an isothermal layer at the bottom of the inversion layer