气候变化领域集成服务门户(CCPortal): A three-dimensional-model inversion of methyl chloroform to constrain the atmospheric oxidative capacity

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DOI	10.5194/acp-21-4809-2021
	A three-dimensional-model inversion of methyl chloroform to constrain the atmospheric oxidative capacity
	Naus S.; Montzka S.A.; Patra P.K.; Krol M.C.
发表日期	2021
ISSN	1680-7316
起始页码	4809
结束页码	4824
卷号	21 期号:6
英文摘要	Variations in the atmospheric oxidative capacity, largely determined by variations in the hydroxyl radical (OH), form a key uncertainty in many greenhouse and other pollutant budgets, such as that of methane (CH4). Methyl chloroform (MCF) is an often-adopted tracer to indirectly put observational constraints on large-scale variations in OH.We investigated the budget of MCF in a 4DVAR inversion using the atmospheric transport model TM5, for the period 1998-2018, with the objective to derive information on large-scale, interannual variations in atmospheric OH concentrations. While our main inversion did not fully converge, we did derive interannual variations in the global oxidation of MCF that bring simulated mole fractions of MCF within 1 %-2% of the assimilated observations from the NOAA-GMD surface network at most sites. Additionally, the posterior simulations better reproduce aircraft observations used for independent validation compared to the prior simulations. The derived OH variations showed robustness with respect to the prior MCF emissions and the prior OH distribution over the 1998 to 2008 period. Although we find a rapid 8% increase in global mean OH concentrations between 2010 and 2012 that quickly declines afterwards, the derived interannual variations were typically small (<3 %/yr), with no significant long-term trend in global mean OH concentrations. The inverse system found strong adjustments to the latitudinal distribution of OH, relative to widely used prior distributions, with systematic increases in tropical and decreases in extra-tropical OH concentrations (both up to 30 %). These spatial adjustments were driven by intrahemispheric biases in simulated MCF mole fractions, which have not been identified in previous studies. Given the large amplitude of these adjustments, which exceeds spread between literature estimates, and a residual bias in the MCF intrahemispheric gradients, we suggest a reversal in the extratropical ocean sink of MCF in response to declining atmospheric MCF abundance (as hypothesized inWennberg et al., 2004). This ocean source provides a more realistic explanation for the biases, possibly complementary to adjustments in the OH distribution. We identified significant added value in the use of a 3D transport model, since it implicitly accounts for variable transport and optimizes the observed spatial gradients of MCF, which is not possible in simpler models. However, we also found a trade-off in computational expense and convergence problems. Despite these convergence problems, the derived OH variations do result in an improved match with MCF observations relative to an interannually repeating prior for OH. Therefore, we consider that variations in OH derived from MCF inversions with 3D models can add value to budget studies of long-lived gases like CH4. © 2021 Author(s).
语种	英语
scopus关键词	annual variation; atmospheric transport; concentration (composition); convergence; hydroxyl radical; inverse analysis; methane; organic compound; three-dimensional modeling; trade-off
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/247017
作者单位	Meteorology and Air Quality, Wageningen University and Research, Wageningen, Netherlands; Halocarbons and other Atmospheric Trace Species (HATS), NOAA Global Monitoring Laboratory, Boulder, CO, United States; Research Institute for Global Change, JAMSTEC, Yokohama, Japan; Center for Environmental Remote Sensing, Chiba University, Chiba, Japan; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands
推荐引用方式 GB/T 7714	Naus S.,Montzka S.A.,Patra P.K.,et al. A three-dimensional-model inversion of methyl chloroform to constrain the atmospheric oxidative capacity[J],2021,21(6).
APA	Naus S.,Montzka S.A.,Patra P.K.,&Krol M.C..(2021).A three-dimensional-model inversion of methyl chloroform to constrain the atmospheric oxidative capacity.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(6).
MLA	Naus S.,et al."A three-dimensional-model inversion of methyl chloroform to constrain the atmospheric oxidative capacity".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.6(2021).