Papers in Meteorology and Geophysics

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A long-range sulfur transport model consisting of two submodels-a meteorological submodel and a dispersion submodel-has been developed to evaluate the extent of acid deposition in East Asia. The Japan Meteorology Agency's operational weather forecasting model was adopted and improved upon, and employed to predict meteorological variables. A Lagrangian particle method was used as the basis for the dispersion model, and a random walk calculation was used for the diffusion process. Dry deposition, below-cloud scavenging, and chemical transformation processes were also included. A numerical simulation was performed for the transport of sulfur oxides in East Asia in 1985, and the annual deposition was evaluated. The results of the simulation showed that the wet deposition of sulfur oxides originating from the Asian continent was roughly 0.05gS/m²/ year, and the dry deposition 0.02-0.17gS/m²/year. The observed wet deposition was about 1.0gS/m²/year, and although uncertain volcanic influence was included in this observed value, it was about 20 times lower than wet deposition of sulfur values observed in Japan. Calculated wet deposition values at four representative receptors were found to be much lower than observed values. Therefore, it was inferred that the contribution from foreign emission sources was extremely low, on the order of around ten percent. An evaluation of the impact of deposition in Kita-Kyushu (in western Japan) showed that emissions from South Korea, Taiwan and the southeastern region of China affected the Kita-Kyushu values. However, an evaluation of the impact of deposition in Niigata (on the Sea of Japan coast) showed that emissions from China dominated.

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A multipurpose field radiometer (Optical Research Corporation Model MSR7000) was modified to measure the degree of polarization and radiance of skylight either on the ground or on a ship. The atmospheric observations were performed over Railroad Valley (38°32'N, 115°44'W), Nevada (USA) where the altitude is 1435m in wavelengths from 400nm to 1000nm. The polarization initially increased with increasing wavelength and reached a maximum of 70% at around 500nm. It then decreased with a further increase of wavelength. This trend might be explained by contamination of aerosols in the atmosphere if the surface reflectance is low. Furthermore, at fixed wavelengths polarization decreased generally with increasing sun elevation, whereas the surface reflectance factor increased. Based on a sun-photometer measurement, the atmospheric aerosols were stable during the measurements. In a simulation in which the surface is assumed to be Lambertian with a fixed reflectance, the skylight polarization decreased with increasing sun elevation. The observed magnitude of changing skylight polarization with solar elevation is smaller than that of simulated results. This might be mainly due to neglecting polarization generated by the surface and partly due to neglecting directional dependence of reflectance.

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