2011 年 26 巻 4 号 p. 286-295
In order to understand the sulfur dry deposition on forests in East Asia, a simplified methodology on deposition velocity estimation was applied to estimate the dry deposition. The simplified method, originally based on the method of Matsuda (2008), can estimate the deposition velocity from wind speed, temperature and relative humidity with hourly or 6-hourly resolutions. The deposition velocities estimated by the simplified method were in good agreement with those by the original method in 2-week average comparison at 5 sites in Japan and 1 site in Thailand, and they are preferably compared with the recent observations. The applications of the simplified method in 27 sites in East Asia from 2003 to 2008 indicated that both SO2 and particulate SO42- deposition velocities on forest surface were higher around Japan and lower around Mongolia and tropical area. The distribution was similar to that of wind speed. Dry deposition of particulate nss-SO42- occupied about 30% of total sulfur dry deposition in the regional average. The ratios were relatively high in remote areas of Japan, because of lower concentrations of SO2 and higher concentrations of particulate nss-SO42-. Ratios of total dry deposition to wet deposition were high at a high latitude and low at a low latitude because of low wind speed and large precipitation at a low latitude.