Global CH<sub>4</sub> fluxes derived from JAXA/GOSAT lower-tropospheric partial column data and the CarbonTracker Europe-CH<sub>4</sub> atmospheric inverse model
<p><span id="page7830"/>Satellite-driven inversions provide valuable information about methane (CH<span class="inline-formula"><sub>4</sub></span>) fluxes, but the assimilation of total column-averaged dry-air mole fractions of CH<span class...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/7829/2025/acp-25-7829-2025.pdf |
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| Summary: | <p><span id="page7830"/>Satellite-driven inversions provide valuable information about methane (CH<span class="inline-formula"><sub>4</sub></span>) fluxes, but the assimilation of total column-averaged dry-air mole fractions of CH<span class="inline-formula"><sub>4</sub></span> (XCH<span class="inline-formula"><sub>4</sub></span>) has been challenging. This study explores, for the first time, the potential of the new lower-tropospheric partial column (pXCH<span class="inline-formula"><sub>4</sub></span>_LT) GOSAT data, retrieved by the Japan Aerospace Exploration Agency (JAXA), to constrain global and regional CH<span class="inline-formula"><sub>4</sub></span> fluxes. Using the CarbonTracker Europe-CH<span class="inline-formula"><sub>4</sub></span> (CTE-CH<span class="inline-formula"><sub>4</sub></span>) atmospheric inverse model, we estimated CH<span class="inline-formula"><sub>4</sub></span> fluxes between 2016–2019 by assimilating the JAXA/GOSAT pXCH<span class="inline-formula"><sub>4</sub></span>_LT and XCH<span class="inline-formula"><sub>4</sub></span> data and surface CH<span class="inline-formula"><sub>4</sub></span> observations independently of each other. The Northern Hemisphere CH<span class="inline-formula"><sub>4</sub></span> fluxes derived from the pXCH<span class="inline-formula"><sub>4</sub></span>_LT data were similar to the estimates derived from the surface observations but were underestimated by about 35 Tg CH<span class="inline-formula"><sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> (<span class="inline-formula">∼</span> 6 % of the global total) using the XCH<span class="inline-formula"><sub>4</sub></span> data. For the Southern Hemisphere, the estimates from both GOSAT inversions were about 15–30 Tg CH<span class="inline-formula"><sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> higher than those derived from surface data. The evaluations against independent data from the Atmospheric Tomography Mission aircraft campaign showed good agreement in the lower-tropospheric CH<span class="inline-formula"><sub>4</sub></span> from the inversions using the pXCH<span class="inline-formula"><sub>4</sub></span>_LT and surface data. However, from these inversions, the modelled north–south gradients showed significant overestimation in the upper troposphere and stratosphere, possibly due to relatively uniform inter-hemispheric OH distributions that control CH<span class="inline-formula"><sub>4</sub></span> sinks. Overall, we found that the use of the JAXA/GOSAT pXCH<span class="inline-formula"><sub>4</sub></span>_LT data shows considerable potential in constraining global and regional CH<span class="inline-formula"><sub>4</sub></span> fluxes, advancing our understanding of the CH<span class="inline-formula"><sub>4</sub></span> budget.</p> |
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| ISSN: | 1680-7316 1680-7324 |