Sudden Change of Surface Inversion of Air Temperature on Suburban Area in the Chiba Prefecture

Abstract

Vertical profile of air temperature is measured by radiosonde set on anchored balloon at a winter night, 3-4 December 1979, under the condition of clear sky and gentle wind. The observations were made at four points distributed in about 15km distance, in northwestern Chiba Prefecture (Fig. 1).Surface inversion appeared before sunset (about 15:30JST). Intensity of inversion increased to midnight and the depth of inversion layer reached 50-75m at midnight. Between 0 to 1JST temperature profile showed sudden change; strong inversion layer is elevated to 50-100m hight and ground based isothermal layer appeared under 50m bight (Fig. 2, 3). The similer change of temperature profile appeared at three suburban observation points except at one point placed in flat grass field. Concentration of NO and NO2 are high within the inversion layer and their vertical profile show simultaneous change with that of inversion (Fig. 4, 5).It is shown by wind field analysis, that the cold northern wind causes the change of temperature profile. The wind is a part of land breeze from Kanto Plain to the Tokyo Bay (Fig. 6, 7). These phenomena appeared at 34 nights during December of 1975-1979 (Table 1, 2 and Fig. 8), which correspond to the occurence frequency of about a half number of nights with clear sky and gentle wind.