Evaluation of SO<sub>2</sub>, SO<sub>4</sub><sup>2−</sup> and an updated SO<sub>2</sub> dry deposition parameterization in the United Kingdom Earth System Model
<p>In this study we evaluate simulated surface <span class="inline-formula">SO<sub>2</sub></span> and sulfate (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline&quo...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/18465/2021/acp-21-18465-2021.pdf |
| Summary: | <p>In this study we evaluate simulated surface <span class="inline-formula">SO<sub>2</sub></span> and sulfate (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="40da026c69d6bb7b362f8aefb7758b92"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00004.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00004.png"/></svg:svg></span></span>) concentrations from the United Kingdom Earth System Model (UKESM1) against observations from ground-based measurement networks in the USA and Europe for the period 1987–2014. We find that UKESM1 captures the historical trend for decreasing concentrations of atmospheric <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="8c898138530c760447165fe6cdc920bb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00005.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00005.png"/></svg:svg></span></span> in both Europe and the USA over the period 1987–2014. However, in the polluted regions of the eastern USA and Europe, UKESM1 over-predicts surface <span class="inline-formula">SO<sub>2</sub></span> concentrations by a factor of 3 while under-predicting surface <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="97cb19aa5ca8b26a6d7fd7d4bad307d2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00006.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00006.png"/></svg:svg></span></span> concentrations by 25 %–35 %. In the cleaner western USA, the model over-predicts both surface <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="14485914c781d9e26f0da54782d5723d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00007.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00007.png"/></svg:svg></span></span> concentrations by factors of 12 and 1.5 respectively. We find that UKESM1’s bias in surface <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="996ea863b6d2357cf65489687f93a05f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00008.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00008.png"/></svg:svg></span></span> concentrations is variable according to region and season. We also evaluate UKESM1 against total column <span class="inline-formula">SO<sub>2</sub></span> from the Ozone Monitoring Instrument (OMI) using an updated data product. This comparison provides information about the model's global performance, finding that UKESM1 over-predicts total column <span class="inline-formula">SO<sub>2</sub></span> over much of the globe, including the large source regions of India, China, the USA, and Europe as well as over outflow regions. Finally, we assess the impact of a more realistic treatment of the model's <span class="inline-formula">SO<sub>2</sub></span> dry deposition parameterization. This change increases <span class="inline-formula">SO<sub>2</sub></span> dry deposition to the land and ocean surfaces, thus reducing the atmospheric loading of <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="47e678c4680581e78f7a83f3b1df9ebc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00009.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00009.png"/></svg:svg></span></span>. In comparison with the ground-based and satellite observations, we find that the modified parameterization reduces the model's over-prediction of surface <span class="inline-formula">SO<sub>2</sub></span> concentrations and total column <span class="inline-formula">SO<sub>2</sub></span>. Relative to the ground-based observations, the simulated surface <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="66431dc7c7d5e1df65243409a551c241"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-18465-2021-ie00010.svg" width="29pt" height="17pt" src="acp-21-18465-2021-ie00010.png"/></svg:svg></span></span> concentrations are also reduced, while the simulated <span class="inline-formula">SO<sub>2</sub></span> dry deposition fluxes increase.</p> |
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| ISSN: | 1680-7316 1680-7324 |