Simulated Seasonal Variations in Wet Acid Depositions over East Asia

Abstract

The air quality modeling system Regional Atmospheric Modeling System-Community Multi-scale Air Quality (RAMS-CMAQ) was applied to analyze temporospatial variations in wet acid deposition over East Asia in 2005, and model results obtained on a monthly basis were evaluated against extensive observations, including precipitation amounts at 704 stations and SO 4 2À , NO 3 À , and NH 4 þ concentrations in the atmosphere and rainwater at 18 EANET (the Acid Deposition Monitoring Network in East Asia) stations. The comparison shows that the modeling system can reasonably reproduce seasonal precipitation patterns, especially the extensive area of dry conditions in northeast China and north China and the major precipitation zones. For ambient concentrations and wet depositions, the simulated results are in reasonable agreement (within a factor of 2) with observations in most cases, and the major observed features are mostly well reproduced. The analysis of modeled wet deposition distributions indicates that East Asia experiences noticeable variations in its wet deposition patterns throughout the year. In winter, southern China and the coastal areas of the Japan Sea report higher SO 4 2À and NO 3 À wet depositions. In spring, elevated SO 4 2À and NO 3 À wet depositions are found in northeastern China, southern China, and around the Yangtze River. In summer, a remarkable rise in precipitation in northeastern China, the valleys of the Huaihe and Yangtze rivers, Korea, and Japan leads to a noticeable increase in SO 4 2À and NO 3 À wet depositions, whereas in autumn, higher SO 4 2À and NO 3 À wet depositions are found around Sichuan Province. Meanwhile, due to the high emission of SO 2 , high wet depositions of SO 4 2À are found throughout the entire year in the area surrounding Sichuan Province. There is a tendency toward decreasing NO 3 À concentrations in rainwater from China through Korea to Japan in both observed and simulated results, which is a consequence of the influence of the continental outflow from Eurasia. The same tendency is not found for SO 4 2À .

Influence of relative humidity on aerosol composition: Impacts on light extinction and visibility impairment at two sites in coastal area of China

“…The similar deficit of cation equivalence was also reported for aerosol over the Yellow Sea and the Bohai Sea (Xue et al, 2011). The simulated high concentrations of sulfate and nitrate over the coastal areas of China (Ge et al, 2011) are also consistent with our result here.…”

Satellite‐based global volcanic SO2 emissions and sulfate direct radiative forcing during 2005–2012

“…Total sulfate AOD includes both anthropogenic and volcanoes sulfate AOD (Figure f). The highest value is located in the middle latitudes of the Northern Hemisphere every summer, and it reflects persistent anthropogenic SO 2 sources over some polluted middle‐latitude countries such as China and a higher formation rate of SO 4 2− from SO 2 in northern summer [ Carmichael et al ., ; Ge et al ., ]. For the big volcanic eruptions listed in Table , the monthly ratios of eruptive SAOD/total SAOD are larger than 40%.…”

“…Most anthropogenic sulfate is from the Northern Hemisphere, especially East Asia (Figure ). Generally, the water vapor content is elevated in summer over the Northern Hemisphere which results in a higher formation rate of SO 4 2− from SO 2 [ Carmichael et al ., ; Ge et al ., ]. The largest monthly mean eruptive volcanic sulfate forcing in recent years is −0.83 W m −2 in June 2011 when Nabro erupted, and it doubled the anthropogenic sulfate forcing during that month.…”

Simulated seasonal variations in nitrogen wet deposition over East Asia

“…However, the fluxes in nitrogen wet deposition were calculated only by using a few sites. A systematic nationwide OPEN ACCESS Downloaded by [79.133.106.13] at 18:28 04 June 2016 2010; Zhang et al , 2012bZhang, Han, and Zhu 2007;Zhang, Shen, et al 2012), in addition to wet acidic depositions (Ge et al 2011), over East Asia. The cloud module in the modeling system includes parameterizations for several types of clouds, including sub-grid convective (precipitating and non-precipitating) and grid-scale resolved.…”