Abstract
The use of a thermistor has enabled to make close observation of the vertical profile of air tempera ture with great ease. Characterized with its high sensitivity, however, the instrument is accompanied with the minute fluctuation, which involves many problems in treating the data thus obtained.
The author succeeded in drawing a curve of this fluctuation (Fig. 4) based on the frequent observations, and found that the curve was composed of periodic waves, large and small. (The lag of the thermistor is 3.5 seconds.) That is to say, it may be true that the minute fluctuation is caused by the turbulent flow in the lower atmosphere, and that each wave corresponds to respective eddy within the main stream.
Thus, he tried to catch the vertical profile of air temperature in a builtup area from the viewpoint of the frequency with these eddies appear. The observation was made on the watchtower (35 meters in height) of the fire station at Takanohashi, Hiroshima City.
Each form of the vertical profile of diurnal air temperature variation obtained by using the thermistor can be explained as a process in which the air warmed on the ground is ascending higher forming micro air masses. And the average results of many observations within a difinite time indicate that a.a plane of sudden change of air temperature lies at a height of about 15 meters (Fig. 6). This is due to the high frequecy of the warm micro air masses in the lower atomosphere within 15 meters in height, and may be explained by the influence of buildings (about 8-15 meters in height) and the vertical structure of the surface wind.
