A machine learning examination of hydroxyl radical differences among model simulations for CCMI-1

Nicely, Julie M.; Duncan, B. N.; Hanisco, T. F.; Wolfe, G. M.; Salawitch, R. J.; Deushi, Makoto; Haslerud, Amund Søvde; Jöckel, Patrick; Josse, B.; Kinnison, Douglas E.; Klekociuk, Andrew; Manyin, Michael; Marécal, Virginie; Morgenstern, Olaf; Murray, Lee T.; Myhre, Gunnar; Oman, Luke D.; Pitari, Giovanni; Pozzer, Andrea; Quaglia, Ilaria; Revell, Laura E.; Rozanov, Eugene; Stenke, Andrea; Stone, Kane; Strahan, S. E.; Tilmes, Simone; Tost, H.; Westervelt, Daniel M.; Zeng, Guang

doi:10.5194/acp-20-1341-2020

Cited by 30 publications

(37 citation statements)

References 69 publications

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“…As shown in Fig.3, negative anomalies of [OH] during El Niño events are dominated by increased OH loss through the reaction with CO in response to enhanced biomass burning (Fig.S3), similar to the conclusions of Rowlinson et al 2019and Nicely et al (2020). During the strong El Niño events in 1982-1983, 1991-1992, and 1997-1998, the OH loss by CO increased by up to 3.4±0.4Tmol yr -1 , 4.5±0.6Tmol yr -1 , and 7.6±0.5Tmol yr -1 , respectively, compared to the mean value of 1980-2010.…”

Section: Factors Controlling Oh Trends and Year-to-year Variabilitysupporting

confidence: 87%

“…All CCMI models simulate positive OH trends from 1980 to 2010 after removing the year-to-year variability ( Fig.1, top panel), consistent with previous analyses of CCMI OH fields Nicely et al, 2020) and model results of the Aerosol and Chemistry Model Intercomparison Project (Stevenson et al, 2020). The multi-model mean [OH]GM-CH4 increased by 0.7×10 5 molec cm -3 from 1980 to 2010.…”

Section: Decadal Oh Trends and Year-to-year Variabilitysupporting

confidence: 86%

“…CC BY 4.0 License. increase in OH primary production is mainly due to an increase in tropospheric water vapor and O3 burden during El Niño events ( Fig.S3 and S12 in Nicely et al (2020)), while the increase in OH secondary production is caused by enhanced NOx emissions (Fig.S3) and O3 formation (Nicely et al (2020) related to biomass burning as well as more HO2 formation by CO+OH. As a result, the OH year-to-year variations found here are much smaller than those estimated by Nguyen et al (2020), who mainly considered the response of OH to CO.…”

Section: Factors Controlling Oh Trends and Year-to-year Variabilitymentioning

confidence: 97%

“…The OH primary production (O ( 1 D)+H2O) shows a large increase of 10.1±1.1Tmol yr -1 from 1980 to 2010, as the dominant driver of the positive OH trend. The increase in OH primary production is due to an increase in both tropospheric O3 burden (producing O( 1 D)) and water vapor Nicely et al, 2020). The OH loss from CO increased by 7.3±0.7Tmol yr -https://doi.org/10.5194/acp-2020-308 Preprint.…”

Section: Factors Controlling Oh Trends and Year-to-year Variabilitymentioning

confidence: 99%

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On the role of trend and variability of hydroxyl radical (OH) in the global methane budget

Zhao¹,

Saunois²,

Bousquet³

et al. 2020

Preprint

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Abstract. Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by ~ 23 Tg yr−1 from 1986 to 2010. The variational inversion estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.

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Section: Factors Controlling Oh Trends and Year-to-year Variabilitysupporting

confidence: 87%

Section: Decadal Oh Trends and Year-to-year Variabilitysupporting

confidence: 86%

Section: Factors Controlling Oh Trends and Year-to-year Variabilitymentioning

confidence: 97%

Section: Factors Controlling Oh Trends and Year-to-year Variabilitymentioning

confidence: 99%

See 2 more Smart Citations

On the role of trend and variability of hydroxyl radical (OH) in the global methane budget

Zhao¹,

Saunois²,

Bousquet³

et al. 2020

Preprint

Self Cite

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“…Also, proxy methods do not allow access to underlying processes as direct chemistry modeling does (Zhao et al, 2019). This paper follows the work of Zhao et al (2019), wherein we analyzed in detail 10 OH fields derived from atmospheric chemistry models considering different chemistry, emissions, and dy- namics (Patra et al, 2011;Szopa et al, 2013;Hegglin and Lamarque, 2015;Morgenstern et al, 2017;Zhao et al, 2019;Terrenoire et al, 2020). We now aim to build on this previous paper to estimate the impact of these OH fields on methane emissions as inferred by an atmospheric 4D variational inversion system.…”

Section: Globalmentioning

confidence: 99%

Influences of hydroxyl radicals (OH) on top-down estimates of the global and regional methane budgets

et al. 2020

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Abstract. The hydroxyl radical (OH), which is the dominant sink of methane (CH4), plays a key role in closing the global methane budget. Current top-down estimates of the global and regional CH4 budget using 3D models usually apply prescribed OH fields and attribute model–observation mismatches almost exclusively to CH4 emissions, leaving the uncertainties due to prescribed OH fields less quantified. Here, using a variational Bayesian inversion framework and the 3D chemical transport model LMDz, combined with 10 different OH fields derived from chemistry–climate models (Chemistry–Climate Model Initiative, or CCMI, experiment), we evaluate the influence of OH burden, spatial distribution, and temporal variations on the global and regional CH4 budget. The global tropospheric mean CH4-reaction-weighted [OH] ([OH]GM-CH4) ranges 10.3–16.3×105 molec cm−3 across 10 OH fields during the early 2000s, resulting in inversion-based global CH4 emissions between 518 and 757 Tg yr−1. The uncertainties in CH4 inversions induced by the different OH fields are similar to the CH4 emission range estimated by previous bottom-up syntheses and larger than the range reported by the top-down studies. The uncertainties in emissions induced by OH are largest over South America, corresponding to large inter-model differences of [OH] in this region. From the early to the late 2000s, the optimized CH4 emissions increased by 22±6 Tg yr−1 (17–30 Tg yr−1), of which ∼25 % (on average) offsets the 0.7 % (on average) increase in OH burden. If the CCMI models represent the OH trend properly over the 2000s, our results show that a higher increasing trend of CH4 emissions is needed to match the CH4 observations compared to the CH4 emission trend derived using constant OH. This study strengthens the importance of reaching a better representation of OH burden and of OH spatial and temporal distributions to reduce the uncertainties in the global and regional CH4 budgets.

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Atmospheric removal of methane by enhancing the natural hydroxyl radical sink

Wang

Ming

et al. 2022

Greenhouse Gases

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According to the latest report from the intergovernmental panel on climate change (IPCC), currently, global warming due to methane (CH4) alone is about 0.5°C while due to carbon dioxide (CO2) alone is about 0.75°C. As CH4 emissions will continue growing, in order to limit warming to 1.5˚C, some of the most effective strategies are rapidly reducing CH4 emissions and developing large scale CH4 removal methods. The aim of this review article is to summarise and propose possible methods for atmospheric CH4 removal, based on the hydroxyl radical (°OH), which is the principal natural sink of many gases in the atmosphere and on many water surfaces. Inspired by mechanisms of °OH generation in the atmosphere and observed or predicted enhancement of °OH by climate change and human activities, we proposed several methods to enhance the °OH sink by some physical means using water vapour and artificial UV radiation. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

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A machine learning examination of hydroxyl radical differences among model simulations for CCMI-1

Cited by 30 publications

References 69 publications

On the role of trend and variability of hydroxyl radical (OH) in the global methane budget

On the role of trend and variability of hydroxyl radical (OH) in the global methane budget

Influences of hydroxyl radicals (OH) on top-down estimates of the global and regional methane budgets

Atmospheric removal of methane by enhancing the natural hydroxyl radical sink

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