# Incorporation of volcanic SO 2 emissions in the Hemispheric CMAQ (H-CMAQ) version 5.2 modeling system and assessing their impacts on sulfate aerosol over the Northern Hemisphere

The state-of-the-science Community Multiscale Air Quality (CMAQ) Modeling System has recently been extended for hemispheric-scale modeling applications (referred to as H-CMAQ). In this study, satellite-constrained estimation of the degassing inline-formulaSO2 emissions from 50 volcanoes over the Northern Hemisphere is incorporated into H-CMAQ, and their impact on tropospheric sulfate aerosol (inline-formula $M4inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg544235742d8f4a0f97153436b699bab8 gmd-14-5751-2021-ie00001.svg29pt17ptgmd-14-5751-2021-ie00001.png ) levels is assessed for 2010. The volcanic degassing improves predictions of observations from the Acid Deposition Monitoring Network in East Asia (EANET), the United States Clean Air Status and Trends Network (CASTNET), and the United States Integrated Monitoring of Protected Visual Environments (IMPROVE). Over Asia, the increased inline-formula $M5inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg28cd4f8c12cf9ef751545712573a522a gmd-14-5751-2021-ie00002.svg29pt17ptgmd-14-5751-2021-ie00002.png concentrations were seen to correspond to the locations of volcanoes, especially over Japan and Indonesia. Over the USA, the largest impacts that occurred over the central Pacific were caused by including the Hawaiian Kilauea volcano, while the impacts on the continental USA were limited to the western portion during summertime. The emissions of the Soufrière Hills volcano located on the island of Montserrat in the Caribbean Sea affected the southeastern USA during the winter season. The analysis at specific sites in Hawaii and Florida also confirmed improvements in regional performance for modeled inline-formula $M6inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimga8455a3a3390243c17ea2f3ca419ac4e gmd-14-5751-2021-ie00003.svg29pt17ptgmd-14-5751-2021-ie00003.png by including volcanoes inline-formulaSO2 emissions. At the edge of the western USA, monthly averaged inline-formula $M8inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg40da026c69d6bb7b362f8aefb7758b92 gmd-14-5751-2021-ie00004.svg29pt17ptgmd-14-5751-2021-ie00004.png enhancements greater than 0.1 inline-formulaµg m−3 were noted within the boundary layer (defined as surface to 750 hPa) during June–September. Investigating the change on inline-formula $M10inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg8c898138530c760447165fe6cdc920bb gmd-14-5751-2021-ie00005.svg29pt17ptgmd-14-5751-2021-ie00005.png concentration throughout the free troposphere revealed that although the considered volcanic inline-formulaSO2 emissions occurred at or below the middle of free troposphere (500 hPa), compared to the simulation without the volcanic source, inline-formula $M12inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg97cb19aa5ca8b26a6d7fd7d4bad307d2 gmd-14-5751-2021-ie00006.svg29pt17ptgmd-14-5751-2021-ie00006.png enhancements of more than 10 % were detected up to the top of the free troposphere (250 hPa). Our model simulations and comparisons with measurements across the Northern Hemisphere indicate that the degassing volcanic inline-formulaSO2 emissions are an important source and should be considered in air quality model simulations assessing background inline-formula $M14inlinescrollmathmlchem{\mathrm{normal SO}}_{normal 4}^{normal 2-}$ 29pt17ptsvg-formulamathimg14485914c781d9e26f0da54782d5723d gmd-14-5751-2021-ie00007.svg29pt17ptgmd-14-5751-2021-ie00007.png levels and their source attribution.

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Itahashi, Syuichi / Mathur, Rohit / Hogrefe, Christian / et al: Incorporation of volcanic SO2 emissions in the Hemispheric CMAQ (H-CMAQ) version 5.2 modeling system and assessing their impacts on sulfate aerosol over the Northern Hemisphere. 2021. Copernicus Publications.

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