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

利用卫星云图和小尺度气象模式，研究赤木山和日光山区雾水化学特征与气象条件的关系，以及酸雾与森林衰退的关系。利用1987、1990、1992年三年的陆地卫星影像资料，对森林退化面积进行了调查。由于卫星影像分辨率不够，无法从影像中找到枯枝落叶的分布，但通过飞机拍摄的照片和实地调查结果可以得出枯枝落叶的分布是非常局部和离散的结论。赤城山区采集的酸化雾水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而异。它能够通过考虑REL…来解释这些特征采样点与污染物排放源之间以及输送空气质量的高空风况之间存在较大差异。从三个角度分析了大气污染物到达目标区的传输过程。其一是对来自覆盖亚洲东部的远距离上风源的输送和扩散的模拟。二是对东京大都市、工业化海滨地区和关东平原周边山区的污染物迁移进行了中尺度分析。第三是赤木山和日光附近的局地风对雾形成的模拟。根据宏观尺度分析，海外对日本岛屿年干湿沉积的平均贡献率分别为硝酸盐约20%和20%，硫酸盐约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，对赤城山顶大气污染物的输送过程进行了模拟。从臭氧浓度的时间序列行为和模型模拟结果可以看出，东京大都市和工业化的海滨地区是污染物的主要来源。较少

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