State-wide California 2020 carbon dioxide budget estimated with OCO-2 and OCO-3 satellite data
<p>Satellite observations are instrumental in observing spatiotemporal variability in carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) concentrations, which can be used to derive fluxes of this greenhouse gas. This study leverages NASA'...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/8475/2025/acp-25-8475-2025.pdf |
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| Summary: | <p>Satellite observations are instrumental in observing spatiotemporal variability in carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) concentrations, which can be used to derive fluxes of this greenhouse gas. This study leverages NASA's Orbiting Carbon Observatory-2 and -3 (OCO-2 and OCO-3, respectively) CO<span class="inline-formula"><sub>2</sub></span> observations with a Gaussian process (GP) machine learning inverse model, a Bayesian nonparametric approach well suited for integrating the unique spatiotemporal characteristics of these satellite observations, to estimate subregional CO<span class="inline-formula"><sub>2</sub></span> fluxes. Utilizing the GEOS-Chem chemical transport model (CTM) to simulate column-average CO<span class="inline-formula"><sub>2</sub></span> concentrations (<span class="inline-formula"><i>X</i></span>CO<span class="inline-formula"><sub>2</sub></span>) for 2020 in California – a period marked by the coronavirus disease (COVID-19) pandemic, drought conditions, and significant wildfire activity – we estimated the state-wide CO<span class="inline-formula"><sub>2</sub></span> emission rates constrained by OCO-2/3. This study developed prior fossil fuel emissions to reflect reduced activities during the COVID-19 pandemic, while net ecosystem exchange (NEE) and fire emissions were derived based on satellite data. GEOS-Chem source-specific <span class="inline-formula"><i>X</i></span>CO<span class="inline-formula"><sub>2</sub></span> concentrations for fossil fuels, NEE, fire, and oceanic sources were simulated coincident to OCO-2/3 <span class="inline-formula"><i>X</i></span>CO<span class="inline-formula"><sub>2</sub></span> retrievals to estimate state-wide sector-specific and total CO<span class="inline-formula"><sub>2</sub></span> emissions. GP inverse model results suggest that annual posterior median fossil fuel emissions were consistent with prior estimates (317.8 and 338.4 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, respectively; 95 % confidence level) and that posterior NEE fluxes had less carbon uptake compared to prior fluxes (<span class="inline-formula">−</span>36.8 vs. <span class="inline-formula">−</span>99.2 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, respectively; 95 % confidence level). Posterior fire CO<span class="inline-formula"><sub>2</sub></span> emissions were estimated to be 68.0 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, which was much lower than a priori estimates (103.3 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>). The total median annual CO<span class="inline-formula"><sub>2</sub></span> emissions for the state of California in 2020 were estimated to be 349.6 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> (range of 272.8–428.6 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>; 95 % confidence level), aligning closely with the prior total estimate of 342.5 Tg CO<span class="inline-formula"><sub>2</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>. This study, for the first time, demonstrates that OCO-2/3 <span class="inline-formula"><i>X</i></span>CO<span class="inline-formula"><sub>2</sub></span> observations can be assimilated into inverse models to estimate state-wide source-specific CO<span class="inline-formula"><sub>2</sub></span> fluxes on a seasonal and annual scale.</p> |
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| ISSN: | 1680-7316 1680-7324 |