Evaluating NO<sub><i>x</i></sub> emissions and their effect on O<sub>3</sub> production in Texas using TROPOMI NO<sub>2</sub> and HCHO
<p>The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor (S5P) satellite is a valuable source of information to monitor the <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions that adversely affect air quality...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/10875/2022/acp-22-10875-2022.pdf |
| Summary: | <p>The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor (S5P) satellite is a valuable source of information to monitor the <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions that adversely affect air quality. We conduct a series of experiments using a <span class="inline-formula">4×4</span> km<span class="inline-formula"><sup>2</sup></span> Comprehensive Air Quality Model with Extensions (CAMx) simulation during April–September 2019 in eastern Texas to evaluate the multiple challenges that arise from reconciling the <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions in model simulations with TROPOMI. We find an increase in <span class="inline-formula">NO<sub>2</sub></span> (<span class="inline-formula">+17</span> % in urban areas) when transitioning from the TROPOMI <span class="inline-formula">NO<sub>2</sub></span> version 1.3 algorithm to the version 2.3.1 algorithm in eastern Texas, with the greatest difference (<span class="inline-formula">+25</span> %) in the city centers and smaller
differences (<span class="inline-formula">+5</span> %) in less polluted areas. We find that lightning
<span class="inline-formula">NO<sub><i>x</i></sub></span> emissions in the model simulation contribute up to 24 % of the column <span class="inline-formula">NO<sub>2</sub></span> in the areas over the Gulf of Mexico and 8% in Texas urban areas. <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions inventories, when using locally resolved inputs, agree with <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions derived from TROPOMI <span class="inline-formula">NO<sub>2</sub></span> version 2.3.1 to within 20 % in most circumstances, with a small <span class="inline-formula">NO<sub><i>x</i></sub></span> underestimate in Dallas–Fort Worth (<span class="inline-formula">−13</span> %) and Houston (<span class="inline-formula">−20</span> %). In the vicinity of large power plant plumes (e.g., Martin Lake and Limestone) we find larger disagreements, i.e., the satellite <span class="inline-formula">NO<sub>2</sub></span> is consistently smaller by 40 %–60 % than the modeled <span class="inline-formula">NO<sub>2</sub></span>, which incorporates measured
stack emissions. We find that TROPOMI is having difficulty distinguishing
<span class="inline-formula">NO<sub>2</sub></span> attributed to power plants from the background <span class="inline-formula">NO<sub>2</sub></span>
concentrations in Texas – an area with atmospheric conditions that cause
short <span class="inline-formula">NO<sub>2</sub></span> lifetimes. Second, the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">NO</mi><mi>x</mi></msub><mo>/</mo><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f837adc6cf557f7adaa12a22c8e80dbd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-10875-2022-ie00001.svg" width="51pt" height="14pt" src="acp-22-10875-2022-ie00001.png"/></svg:svg></span></span> ratio in the model may be underestimated due to the 4 km grid cell size. To understand ozone formation regimes in the area, we combine <span class="inline-formula">NO<sub>2</sub></span> column information with formaldehyde (HCHO) column information. We find modest low biases in the model relative to TROPOMI HCHO, with <span class="inline-formula">−9</span> % underestimate in eastern Texas and <span class="inline-formula">−21</span> % in areas of central Texas with lower biogenic volatile organic compound (VOC) emissions. Ozone formation regimes at the time of the early afternoon overpass are <span class="inline-formula">NO<sub><i>x</i></sub></span> limited almost everywhere in the domain, except along the Houston Ship Channel, near the Dallas/Fort Worth International airport, and in the presence of undiluted power plant plumes. There are likely <span class="inline-formula">NO<sub><i>x</i></sub></span>-saturated ozone formation conditions in the early morning hours that TROPOMI cannot observe and would be well-suited for analysis with <span class="inline-formula">NO<sub>2</sub></span> and HCHO from the upcoming TEMPO (Tropospheric Emissions: Monitoring Pollution) mission. This study highlights that TROPOMI measurements offer a valuable means to validate emissions inventories and ozone formation regimes, with important limitations.</p> |
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| ISSN: | 1680-7316 1680-7324 |