Evaluating tropospheric nitrogen dioxide in UKCA using OMI satellite retrievals over south and east Asia
<p>We compare tropospheric column nitrogen dioxide (<span class="inline-formula">NO<sub>2</sub></span>) in the United Kingdom Chemistry and Aerosol (UKCA) model version 11.0 with satellite measurements from NASA's Earth Observing System (EOS) Aura satelli...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/4785/2025/acp-25-4785-2025.pdf |
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| Summary: | <p>We compare tropospheric column nitrogen dioxide (<span class="inline-formula">NO<sub>2</sub></span>) in the United Kingdom Chemistry and Aerosol (UKCA) model version 11.0 with satellite measurements from NASA's Earth Observing System (EOS) Aura satellite Ozone Monitoring Instrument (OMI) to investigate the seasonality and trends of tropospheric <span class="inline-formula">NO<sub>2</sub></span> over south and east Asia (S and E Asia). UKCA is the atmospheric composition component of the UK Earth System Model (UKESM). UKCA was run with nudged meteorology, producing hourly output over S and E Asia for 2005–2015. OMI averaging kernels have been applied to the model hourly data sampled at Aura's local overpass time of 13:45 LT <span class="inline-formula">±</span> 15 min to allow for consistent model–data comparison. Background UKCA and OMI tropospheric column <span class="inline-formula">NO<sub>2</sub></span> typically ranges between <span class="inline-formula">0×10<sup>15</sup></span> and <span class="inline-formula">2×10<sup>15</sup></span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">molec</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">cm</mi><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="60pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="2754044258d9cb5ecfc3c4229425567e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-4785-2025-ie00001.svg" width="60pt" height="13pt" src="acp-25-4785-2025-ie00001.png"/></svg:svg></span></span>. Diurnal cycles and vertical profiles of the tropospheric <span class="inline-formula">NO<sub>2</sub></span> column in UKCA show that the daily minimum tropospheric column <span class="inline-formula">NO<sub>2</sub></span> occurs around the satellite overpass time. UKCA captures the seasonality but overestimates <span class="inline-formula">NO<sub>2</sub></span> by a factor of <span class="inline-formula">∼</span> 2.5, especially during winter over eastern China and north India, at times and locations with high aerosol loadings. Heterogeneous chemistry is represented in the version of UKCA used here as uptake of <span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span> on internally generated sulfate aerosol. However, aerosol surface area may be underestimated in polluted locations, contributing to overestimation of <span class="inline-formula">NO<sub>2</sub></span>. In addition, the model may underestimate emissions of volatile organic compounds (VOCs) and associated peroxy acetyl nitrate (PAN) formation, leading to insufficient long-range transport of oxidised nitrogen and also contributing to overestimation of <span class="inline-formula">NO<sub>2</sub></span> over polluted regions and underestimation over remote regions. Quantifying and understanding discrepancies in modelled <span class="inline-formula">NO<sub>2</sub></span> warrant further investigation as they propagate into modelling of multiple environmental issues.</p> |
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| ISSN: | 1680-7316 1680-7324 |