Cross-evaluating WRF-Chem v4.1.2, TROPOMI, APEX, and in situ NO<sub>2</sub> measurements over Antwerp, Belgium
<p>The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is employed as an intercomparison tool for validating TROPOspheric Monitoring Instrument (TROPOMI) satellite NO<span class="inline-formula"><sub>2</sub></span> retrievals against h...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/16/479/2023/gmd-16-479-2023.pdf |
| Summary: | <p>The Weather Research and Forecasting model coupled with
Chemistry (WRF-Chem) is employed as an intercomparison tool for validating
TROPOspheric Monitoring Instrument (TROPOMI) satellite NO<span class="inline-formula"><sub>2</sub></span> retrievals
against high-resolution Airborne Prism EXperiment (APEX) remote sensing
observations performed in June 2019 in the region of Antwerp, a major
hotspot of NO<span class="inline-formula"><sub>2</sub></span> pollution in Europe. The model is first evaluated using
meteorological and chemical observations in this area. Sensitivity
simulations varying the model planetary layer boundary (PBL)
parameterization were conducted for a 3 d period in June 2019, indicating
a generally good performance of most parameterizations against
meteorological data (namely ceilometer, surface meteorology, and balloon
measurements), except for a moderate overestimation (<span class="inline-formula">∼</span> 1 m s<span class="inline-formula"><sup>−1</sup></span>) of near-surface wind speed. On average, all but one of the PBL schemes reproduce the surface NO<span class="inline-formula"><sub>2</sub></span> measurements at stations of the Belgian Interregional Environmental Agency fairly well, although surface NO<span class="inline-formula"><sub>2</sub></span> is generally underestimated during the day (between <span class="inline-formula">−4.3</span> % and <span class="inline-formula">−25.1</span> % on average) and overestimated at night (8.2 %–77.3 %). This discrepancy in the diurnal evolution arises despite (1) implementing a detailed representation of the diurnal cycle of emissions (Crippa et al., 2020) and (2) correcting the modeled concentrations to account for measurement interferences due to NO<span class="inline-formula"><sub><i>y</i></sub></span> reservoir species, which increases NO<span class="inline-formula"><sub>2</sub></span> concentrations by about 20 % during the day. The model is further evaluated by comparing a 15 d simulation with surface NO<span class="inline-formula"><sub>2</sub></span>, NO, CO, and O<span class="inline-formula"><sub>3</sub></span> data in the Antwerp region. The modeled daytime NO<span class="inline-formula"><sub>2</sub></span> concentrations are more negatively biased during weekdays than during weekends, indicating a misrepresentation of the weekly temporal profile applied to the emissions obtained from Crippa et al. (2020). Using a mass balance approach, we determined a new weekly profile of NO<span class="inline-formula"><sub><i>x</i></sub></span> emissions, leading to a homogenization of the relative bias among the different weekdays. The ratio of weekend to weekday emissions is significantly lower in this updated profile (0.6) than in the profile based on Crippa et al. (2020; 0.84).</p>
<p>Comparisons with remote sensing observations generally show a good reproduction of the spatial patterns of NO<span class="inline-formula"><sub>2</sub></span> columns by the model. The
model underestimated both APEX (by ca. <span class="inline-formula">−37</span> %) and TROPOMI columns (ca. <span class="inline-formula">−25</span> %) on 27 June, whereas no significant bias is found on 29 June. The
two datasets are intercompared by using the model as an intermediate
platform to account for differences in vertical sensitivity through the
application of averaging kernels. The derived bias of TROPOMI v1.3.1
NO<span class="inline-formula"><sub>2</sub></span> with respect to APEX is about <span class="inline-formula">−10</span> % for columns between
(6–12) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>15</sup></span> molec. cm<span class="inline-formula"><sup>−2</sup></span>. The obtained bias for TROPOMI v1.3.1 increases with the NO<span class="inline-formula"><sub>2</sub></span> column, following <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M26" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>C</mi><mi mathvariant="normal">APEX</mi></msub><mo>=</mo><mn mathvariant="normal">1.217</mn><msub><mi>C</mi><mrow><mi mathvariant="normal">v</mi><mn mathvariant="normal">1.3</mn></mrow></msub><mo>-</mo><mn mathvariant="normal">0.783</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="133pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e59713e3fe4f375854a9822b62ec07ff"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-16-479-2023-ie00001.svg" width="133pt" height="12pt" src="gmd-16-479-2023-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>15</sup></span> molec. cm<span class="inline-formula"><sup>−2</sup></span>, in line with previous validation campaigns. The bias is slightly lower for the reprocessed TROPOMI v2.3.1, with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>C</mi><mi mathvariant="normal">APEX</mi></msub><mo>=</mo><mn mathvariant="normal">1.055</mn><msub><mi>C</mi><mi mathvariant="normal">PAL</mi></msub><mo>-</mo><mn mathvariant="normal">0.437</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="132pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="d0ef8328da635b15c5db332b86c78160"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-16-479-2023-ie00002.svg" width="132pt" height="12pt" src="gmd-16-479-2023-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>15</sup></span> molec. cm<span class="inline-formula"><sup>−2</sup></span> (PAL).</p>
<p>Finally, a mass balance approach was used to perform a crude inversion of
NO<span class="inline-formula"><sub><i>x</i></sub></span> emissions based on 15 d averaged TROPOMI columns. The emission
correction is conducted only in regions with high columns and high
sensitivity to emission changes in order to minimize the errors due to wind
transport. The results suggest that emissions increase over Brussels–Antwerp (<span class="inline-formula">+20</span> %), the Ruhr Valley (13 %), and especially Paris (<span class="inline-formula">+39</span> %), and emissions decrease above a cluster of power plants in western Germany.</p> |
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| ISSN: | 1991-959X 1991-9603 |