盆地を中心とした立体風系による大気汚染物質輸送過程の夏季の特徴 : 津山盆地の事例
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Some Features of Air Pollutants Transport Processes in Summer Driven by Three-dimensional Wind Distributions in Basins : The sample of Tsuyama basin
The relation between the staying time of air pollutants inside Tsuyama basin and their path was studied based on the three-dimensional wind distributions, in summer time (from August 10 to August 29,1991). The measured data on the direction of wind and the speed are provided by AMEDAS. By the interpolation of those data with use of the so-called 'Mathew-model', we predicted the three-dimensional wind distributions. The path, the time and the pattern of air pollutants were obtained by means of the trace analysis, where the air pollutants were treated as quasi-particles. As the result, it was shown that the quasi-particles released around the noon stay inside the basin for short time and those released around the midnight stay inside the basin for long time. The staying time depends on the distribution of the direction and the speed of wind in basin. Because we have the east and west extents longer than the south and north ones in Tsuyama basin, we presume that the staying time of the air pollutants should depend on the direction of their path. In order to study the relation between the pattern of trace and the staying time, we introduced the following two indices, F and β. F is the ratio of the east-west component of the trace to the south-north one. β is the averaged speed of quasi-particles in the three-dimensional wind distribution. The obtained results showed that the large F and the small β caused a long staying time inside the basin as our presumption.
広島大学総合科学部紀要. IV, 理系編