Model Analysis of Inter-annual Variations of Sulfur Deposition in Japan

Abstract

The Community Multi-scale Air Quality (CMAQ) modeling system coupled with the Regional Atmospheric Modeling System (RAMS) and year-by-year emission inventory in Asia (REAS ver. 1.1) was applied to East Asia to analyze inter-annual variation and their factor for nss-SO₄ ²-deposition from 1995 to 2003. The average value of 18 monitoring stations excluding Ogasawara which leaves from the Japan main island that measured throughout the period 1995 to 2003 increase from 1999. CMAQ can reproduce the feature of measured trend and time variation. Then, the model was applied to examine three factors responsible for the variation of Japanese nss-SO₄^2- deposition, meteorology, SO₂ emission from Miyakejima, and SO₂ emission from the other sources. The inter-annual meteorological variation in East Asia influences Japanese nss-SO₄ ^2- deposition, and is a major cause of the interannual variation of Japanese nss-SO₄^2- deposition. Miyakejima volcano has a large impact on the variation of Japanese nss-SO₄^2- deposition in 2001, but that impact is small after 2002. The trend of Japanese nss-SO₄^2- deposition caused by SO₂ emission from other than Miyakejima has been increased after 2000, which correlated well with Chinese SO₂ emission. It is suggested that Chinese SO₂ emission largely affects Japanese nss-SO₄^2- deposition, In west Japan, meteorological variation and trend of SO₂ emission in East Asia have a large influence on inter-annual variation of nss-SO₄ ^2- deposition and the trend of nss-SO₄ ^2- deposition, respectively, because Miyakejima emission has little impacts on nss-SO₄^2- deposition, and Chinese emission has also a large effect on the trend of nss-SO₄^2- deposition than contribution to Japan.