Natural emissions of VOC and NO<sub><i>x</i></sub> over Africa constrained by TROPOMI HCHO and NO<sub>2</sub> data using the MAGRITTEv1.1 model
<p>Natural emissions (vegetation, soil, and lightning) are the dominant sources of non-methane biogenic volatile organic compounds (BVOCs) and nitrogen oxides (NO<span class="inline-formula"><sub><i>x</i></sub>≡</span> NO <span class="inlin...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/2863/2025/acp-25-2863-2025.pdf |
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| Summary: | <p>Natural emissions (vegetation, soil, and lightning) are the dominant sources of non-methane biogenic volatile organic compounds (BVOCs) and nitrogen oxides (NO<span class="inline-formula"><sub><i>x</i></sub>≡</span> NO <span class="inline-formula">+</span> NO<span class="inline-formula"><sub>2</sub></span>) released into the atmosphere over Africa. BVOCs and NO<span class="inline-formula"><sub><i>x</i></sub></span> interact with each other and strongly impact their own chemical lifetimes and degradation pathways, in particular through their influence on hydroxyl radical levels. To account for this intricate interplay between NO<span class="inline-formula"><sub><i>x</i></sub></span> and VOCs, we design and apply a novel inversion setup aiming at simultaneous optimization of monthly VOC and NO<span class="inline-formula"><sub><i>x</i></sub></span> emissions in 2019 in a regional chemistry-transport model, based on Tropospheric Ozone Monitoring Instrument (TROPOMI) HCHO and NO<span class="inline-formula"><sub>2</sub></span> satellite observations. The TROPOMI-based inversions suggest substantial underestimations of natural NO<span class="inline-formula"><sub><i>x</i></sub></span> and VOC emissions used as a priori in the model. The annual flux over Africa increases from 125 to 165 Tg yr<span class="inline-formula"><sup>−1</sup></span> for isoprene, from 1.9 to 2.4 TgN yr<span class="inline-formula"><sup>−1</sup></span> for soil NO emissions, and from 0.5 to 2.0 TgN yr<span class="inline-formula"><sup>−1</sup></span> for lightning NO emissions. Despite the NO<span class="inline-formula"><sub><i>x</i></sub></span> emission increase, evaluation against in situ NO<span class="inline-formula"><sub>2</sub></span> measurements at seven rural sites in western Africa displays significant model underestimations after optimization. The large increases in lightning emissions are supported by comparisons with TROPOMI cloud-sliced upper-tropospheric NO<span class="inline-formula"><sub>2</sub></span> volume mixing ratios, which remain underestimated by the model even after optimization. Our study strongly supports the application of a bias correction to the TROPOMI HCHO data and the use of a two-species constraint (vs. single-species inversion), based on comparisons with isoprene columns retrieved from the Cross-track Infrared Sensor (CrIS).</p> |
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| ISSN: | 1680-7316 1680-7324 |