Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes
<p>The flux divergence approach (FDA) is a popular technique for deriving <span class="inline-formula">NO<sub><i>x</i></sub></span> emission estimates from tropospheric <span class="inline-formula">NO<sub>2</sub></spa...
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Copernicus Publications
2025-02-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/18/621/2025/gmd-18-621-2025.pdf |
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| author | F. Cifuentes F. Cifuentes H. Eskes E. Dammers E. Dammers C. Bryan F. Boersma F. Boersma |
| author_facet | F. Cifuentes F. Cifuentes H. Eskes E. Dammers E. Dammers C. Bryan F. Boersma F. Boersma |
| author_sort | F. Cifuentes |
| collection | DOAJ |
| description | <p>The flux divergence approach (FDA) is a popular technique for deriving <span class="inline-formula">NO<sub><i>x</i></sub></span> emission estimates from tropospheric <span class="inline-formula">NO<sub>2</sub></span> columns measured by the TROPOspheric Monitoring Instrument (TROPOMI) satellite sensor. An attractive aspect of the FDA is that the method simplifies three-dimensional atmospheric chemistry and transport processes into a two-dimensional (longitude–latitude) steady-state continuity equation for columns that balances local <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions with the net outflow and chemical loss of <span class="inline-formula">NO<sub><i>x</i></sub></span>. Here we test the capability of the FDA to reproduce known <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions from synthetic <span class="inline-formula">NO<sub>2</sub></span> column retrievals generated with the LOTOS-EUROS chemistry transport model over the Netherlands at high spatial resolution of about <span class="inline-formula">2×2</span> <span class="inline-formula">km</span> during summer. Our results show that the FDA captures the magnitude and spatial distribution of the <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions to high accuracy (absolute bias <span class="inline-formula"><9</span> %), provided that the observations represent the <span class="inline-formula">NO<sub>2</sub></span> column in the boundary layer, that wind speed and direction are representative for the boundary layer (PBL) column, and that the high-resolution spatiotemporal variability of the <span class="inline-formula">NO<sub>2</sub></span> lifetimes and <span class="inline-formula">NO<sub><i>x</i></sub>:NO<sub>2</sub></span> ratio is accounted for in the inversion instead of using single fixed values. The FDA systematically overestimates <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions by 15 %–60 % when using tropospheric <span class="inline-formula">NO<sub>2</sub></span> columns as the driving observation, while using PBL <span class="inline-formula">NO<sub>2</sub></span> columns largely overcomes this systematic error. This merely reflects the fact that the local balance between emissions and sinks of <span class="inline-formula">NO<sub><i>x</i></sub></span> occurs in the boundary layer, which is decoupled from the <span class="inline-formula">NO<sub>2</sub></span> in the free troposphere. Based on the recommendations from this sensitivity test, we then applied the FDA using observations of <span class="inline-formula">NO<sub>2</sub></span> columns from TROPOMI, corrected for contributions from free-tropospheric <span class="inline-formula">NO<sub>2</sub></span>, between 1 June and 31 August 2018. The <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions derived from the default TROPOMI retrievals are biased low over cities and industrialized areas. However, when the coarse <span class="inline-formula">1×1</span>° TM5-MP <span class="inline-formula">NO<sub>2</sub></span> profile used in the retrieval is replaced by the high-resolution profile of LOTOS-EUROS, the TROPOMI <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions are enhanced by 22 % and are in better agreement with the inventory for the Netherlands. This emphasizes the importance of using realistic high-resolution a priori <span class="inline-formula">NO<sub>2</sub></span> profile shapes in the TROPOMI retrieval. We conclude that accurate quantitative <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions estimates are possible with the FDA, but they require sophisticated, fine-scale corrections for both the <span class="inline-formula">NO<sub>2</sub></span> observations driving the method and the estimates of the <span class="inline-formula">NO<sub>2</sub></span> chemical lifetime and <span class="inline-formula">NO<sub><i>x</i></sub>:NO<sub>2</sub></span> ratio. This information can be obtained from high-resolution chemistry transport model simulations at the expense of the simplicity and applicability of the FDA.</p> |
| format | Article |
| id | doaj-art-13582077f14a44669b82843f5bb31e65 |
| institution | Kabale University |
| issn | 1991-959X 1991-9603 |
| language | English |
| publishDate | 2025-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Geoscientific Model Development |
| spelling | doaj-art-13582077f14a44669b82843f5bb31e652025-02-05T10:21:14ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032025-02-011862164910.5194/gmd-18-621-2025Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapesF. Cifuentes0F. Cifuentes1H. Eskes2E. Dammers3E. Dammers4C. Bryan5F. Boersma6F. Boersma7R&D Satellite Observation department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, the NetherlandsMeteorology and Air Quality Department, Wageningen University & Research (WUR), Wageningen, 6708 PB, the NetherlandsR&D Satellite Observation department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, the NetherlandsAir Quality and Emissions Research, Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, 3584 CB, the NetherlandsInstitute of Environmental Sciences (CML), Leiden University, Leiden, 2333 CC, the NetherlandsR&D Satellite Observation department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, the NetherlandsR&D Satellite Observation department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, the NetherlandsMeteorology and Air Quality Department, Wageningen University & Research (WUR), Wageningen, 6708 PB, the Netherlands<p>The flux divergence approach (FDA) is a popular technique for deriving <span class="inline-formula">NO<sub><i>x</i></sub></span> emission estimates from tropospheric <span class="inline-formula">NO<sub>2</sub></span> columns measured by the TROPOspheric Monitoring Instrument (TROPOMI) satellite sensor. An attractive aspect of the FDA is that the method simplifies three-dimensional atmospheric chemistry and transport processes into a two-dimensional (longitude–latitude) steady-state continuity equation for columns that balances local <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions with the net outflow and chemical loss of <span class="inline-formula">NO<sub><i>x</i></sub></span>. Here we test the capability of the FDA to reproduce known <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions from synthetic <span class="inline-formula">NO<sub>2</sub></span> column retrievals generated with the LOTOS-EUROS chemistry transport model over the Netherlands at high spatial resolution of about <span class="inline-formula">2×2</span> <span class="inline-formula">km</span> during summer. Our results show that the FDA captures the magnitude and spatial distribution of the <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions to high accuracy (absolute bias <span class="inline-formula"><9</span> %), provided that the observations represent the <span class="inline-formula">NO<sub>2</sub></span> column in the boundary layer, that wind speed and direction are representative for the boundary layer (PBL) column, and that the high-resolution spatiotemporal variability of the <span class="inline-formula">NO<sub>2</sub></span> lifetimes and <span class="inline-formula">NO<sub><i>x</i></sub>:NO<sub>2</sub></span> ratio is accounted for in the inversion instead of using single fixed values. The FDA systematically overestimates <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions by 15 %–60 % when using tropospheric <span class="inline-formula">NO<sub>2</sub></span> columns as the driving observation, while using PBL <span class="inline-formula">NO<sub>2</sub></span> columns largely overcomes this systematic error. This merely reflects the fact that the local balance between emissions and sinks of <span class="inline-formula">NO<sub><i>x</i></sub></span> occurs in the boundary layer, which is decoupled from the <span class="inline-formula">NO<sub>2</sub></span> in the free troposphere. Based on the recommendations from this sensitivity test, we then applied the FDA using observations of <span class="inline-formula">NO<sub>2</sub></span> columns from TROPOMI, corrected for contributions from free-tropospheric <span class="inline-formula">NO<sub>2</sub></span>, between 1 June and 31 August 2018. The <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions derived from the default TROPOMI retrievals are biased low over cities and industrialized areas. However, when the coarse <span class="inline-formula">1×1</span>° TM5-MP <span class="inline-formula">NO<sub>2</sub></span> profile used in the retrieval is replaced by the high-resolution profile of LOTOS-EUROS, the TROPOMI <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions are enhanced by 22 % and are in better agreement with the inventory for the Netherlands. This emphasizes the importance of using realistic high-resolution a priori <span class="inline-formula">NO<sub>2</sub></span> profile shapes in the TROPOMI retrieval. We conclude that accurate quantitative <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions estimates are possible with the FDA, but they require sophisticated, fine-scale corrections for both the <span class="inline-formula">NO<sub>2</sub></span> observations driving the method and the estimates of the <span class="inline-formula">NO<sub>2</sub></span> chemical lifetime and <span class="inline-formula">NO<sub><i>x</i></sub>:NO<sub>2</sub></span> ratio. This information can be obtained from high-resolution chemistry transport model simulations at the expense of the simplicity and applicability of the FDA.</p>https://gmd.copernicus.org/articles/18/621/2025/gmd-18-621-2025.pdf |
| spellingShingle | F. Cifuentes F. Cifuentes H. Eskes E. Dammers E. Dammers C. Bryan F. Boersma F. Boersma Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes Geoscientific Model Development |
| title | Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes |
| title_full | Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes |
| title_fullStr | Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes |
| title_full_unstemmed | Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes |
| title_short | Accurate space-based NO<sub><i>x</i></sub> emission estimates with the flux divergence approach require fine-scale model information on local oxidation chemistry and profile shapes |
| title_sort | accurate space based no sub i x i sub emission estimates with the flux divergence approach require fine scale model information on local oxidation chemistry and profile shapes |
| url | https://gmd.copernicus.org/articles/18/621/2025/gmd-18-621-2025.pdf |
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