Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010

Abstract

Abstract. Anthropogenic SO 2 emissions increased alongside economic development in China at a rate of 12.7 % yr −1 from 2000 to 2005. However, under new Chinese government policy, SO 2 emissions declined by 3.9 % yr −1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 3-8 % yr −1 to a peak around [2005][2006] and subsequently decreased by 2-7 % yr −1 , based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO 2 emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70 % of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO 2 emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO 2 vertical column density and bottom-up SO 2 emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO 2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO 2 emissions and satellite retrieval. Satellite measurements of fine-mode AOD above the Sea of Japan marked a 4.1 % yr −1 decline between 2007 and 2010, which corresponded to the 9 % yr −1 decline in SO 2 emissions from China during the same period.

A 15-year record (2001–2015) of the ratio of nitrate to non-sea-salt sulfate in precipitation over East Asia

“…In our previous studies (Itahashi et al, 2014a(Itahashi et al, , 2015, which considered data obtained in 2000-2011, emissions from China exhibited a transition from a continuously increasing trend. NO x emissions in China have been rising steadily (Kurokawa et al, 2013;Itahashi et al, 2014b), whereas SO 2 emissions in China peaked in [2005][2006] and subsequently declined due to the introduction of flue-gas desulfurization systems in China's 11th Five-Year Plan (2006 (Kurokawa et al, 2013;Itahashi et al, 2012). Recently, it has been reported that NO x emissions in China declined after 2011-2012 (Irie et al, 2016;Xia et al, 2016;Krotkov et al, 2016;van der A et al, 2017).…”

Regional modeling of tropospheric NO<sub>2</sub> vertical column density over East Asia during the period 2000–2010: comparison with multisatellite observations

“…CMAQ modeling systems have been used extensively for atmospheric environmental research over East Asia (e.g., He et al, 2007;Uno et al, 2007;Han et al, 2009;Itahashi et al, 2012aItahashi et al, , 2012bItahashi et al, , 2013. In this study, the meteorological fields were generated by the Weather Research and Forecasting (WRF) model version 3.3 with the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data (FNL; S. Itahashi et al: Regional modeling of tropospheric NO 2 vertical column density over East Asia 3625 http://rda.ucar.edu/datasets/ds083.2/).…”

A 15-year record (2001–2015) of the ratio of nitrate to non-seasalt sulfate in precipitation over East Asia

“…The level over China was about tenfold that of Japan, and the level over Korea was almost twice that over Japan (Fig. 2 (e (Itahashi et al, 2012(Itahashi et al, , 2014a(Itahashi et al, , 2015. China, though these trends were not significant.…”