An Analysis of Acid Fog Effect by Satellite Image Data and Local Scale Meteorological Model Simulation

利用卫星影像和微尺度气象模型，研究赤城山和日光山区雾水化学特征与气象条件的关系，以及酸雾与森林退化的关系。结果，以下几个方面变得清晰起来。利用1987年、1990年和1992年3年的LANDSAT卫星影像资料查询了森林退化面积。由于卫星影像的分辨率不够，无法从影像中找到凋落树的分布，但结合飞机照片和野外调查结果，认为凋落树分布非常局部和离散。赤城山区雾水酸化的主要污染物是硝酸盐，而不是硫酸盐。雾水中化学物质的组成因天气条件的不同而不同。考虑到采样点与污染物排放源之间的关系，以及高空输送气团的风况，可以很好地解释该特征。从三个角度分析了大气污染物到达目标区的输送过程。一是模拟覆盖东亚的远距离逆风源的输送和扩散。二是对东京都市区、工业化滨海地区和关东平原周边山区的污染物转移进行中尺度分析。第三是模拟赤城山和日光附近当地风形成的雾。根据宏观尺度分析，国外对日本岛屿年干湿沉积的平均贡献分别为硝酸盐的20%和20%，硫酸盐的15%和40%。火山喷发的贡献是硫酸盐沉积的重要因素。利用中尺度模式模拟得到的局地风场，估计了大气污染物到达赤城山顶的输送过程。从臭氧浓度的时间序列变化特征和模式模拟结果可以看出，污染物主要来自东京都市区和沿海工业化地区。少

An objective of the study is to define the relationship between chemical characteristics of fog water and meteorological condition, and the relation of acid fog and forest decline of mountainous area Mt.Akagi and Nikko by using a satellite image and a microscale meteorological model.As a result, the following aspects became clear.1. The areas of declined forest were inquired by the LANDSAT satellite image data for three years of 1987,1990, and 1992. As the resolution of satellite image was not sufficient, it was impossible to find the distribution of declined tree from the image, but it was concluded that the blighted tree had distributed very partially and discretely by looking photograph from aircraft, field survey results.2. The main pollutants acidifying fog water sampled at Akagi mountainous area is nitrate rather than sulfate. The composition of chemical species in fog water differs according to weather conditions. It was able to explain the characteristics by considering the rel … More ation between sampling point and emission source of pollutants, and the upper wind condition transporting air mass.3. Transportation process of air pollutants arriving at the objective area, were analyzed from three standpoints. One was a simulation of transport and diffusion from long distant upwind source covering eastem Asia. Second was a mesoscale analysis of pollutants transfer covering metropolitan Tokyo, industrialized seaside area, and mountainous area surrounding the Kanto plain. Third was a simulation of fog formation by local wind near Mt.Akagi and Nikko. According to macroscale analysis, the mean contribution to Japan islands from abroad for annual dry and wet depositions is about 20% and 20% on nitrate, and about 15% and 40% on sulfate, respectively. A contribution of volcanic emission is an important factor to deposition of sulfate. A transportation process of air pollutants arriving at the top of Mt.Akagi was estimated by local wind field gained from mesoscale model simulation. From the behavior of time series ozone concentration and the model simulation results, it was showed that much pollutants have come from metropolitan Tokyo and the industrialized seaside area. Less