气候变化领域集成服务门户(CCPortal): The impact of sulfur hexafluoride (SF6) sinks on age of air climatologies and trends

CCPortal

DOI	10.5194/acp-22-1175-2022
	The impact of sulfur hexafluoride (SF6) sinks on age of air climatologies and trends
	Loeffel, Sheena; Eichinger, Roland; Garny, Hella; Reddmann, Thomas; Fritsch, Frauke; Versick, Stefan; Stiller, Gabriele; Haenel, Florian
发表日期	2022
ISSN	1680-7316
EISSN	1680-7324
起始页码	1175
结束页码	1193
卷号	22 期号:2 页码:19
英文摘要	Mean age of air (AoA) is a common diagnostic for the strength of the stratospheric overturning circulation in both climate models and observations. AoA climatologies and AoA trends over the recent decades of model simulations and proxies derived from observations of long-lived tracers do not agree. Satellite observations show much older air than climate models, and while most models compute a clear decrease in AoA over the last decades, a 30-year time series from measurements shows a statistically nonsignificant positive trend in the Northern Hemisphere extratropical middle stratosphere. Measurement-based AoA derivations are often founded on observations of the trace gas sulfur hexafluoride (SF6), a fairly long-lived gas with a near-linear increase in emissions during recent decades. However, SF6 has chemical sinks in the mesosphere that are not considered in most model studies. In this study, we explicitly compute the chemical SF6 sinks based on chemical processes in the global chemistry climate model EMAC (ECHAM/MESSy Atmospheric Chemistry). We show that good agreement between stratospheric AoA in EMAC and MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is reached through the inclusion of chemical SF6 sinks, as these sinks lead to a strong increase in the stratospheric AoA and, therefore, to a better agreement with MIPAS satellite observations. Remaining larger differences at high latitudes are addressed, and possible reasons for these differences are discussed. Subsequently, we demonstrate that the AoA trends are also strongly influenced by the chemical SF6 sinks. Under consideration of the SF6 sinks, the AoA trends over the recent decades reverse sign from negative to positive. We conduct sensitivity simulations which reveal that this sign reversal does not result from trends in the stratospheric circulation strength nor from changes in the strength of the SF6 sinks We illustrate that even a constant SF6 destruction rate causes a positive trend in the derived AoA, as the amount of depleted SF6 scales with increasing SF6 abundance itself. In our simulations, this effect overcompensates for the impact of the accelerating stratospheric circulation which naturally decreases AoA. Although various sources of uncertainties cannot be quantified in detail in this study, our results suggest that the inclusion of SF6 depletion in models has the potential to reconcile the AoA trends of models and observations. We conclude the study with a first approach towards a correction to account for SF6 loss and deduce that a linear correction might be applicable to values of AoA of up to 4 years.
学科领域	Environmental Sciences; Meteorology & Atmospheric Sciences
语种	英语
WOS研究方向	Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000748747400001
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/273792
作者单位	Helmholtz Association; German Aerospace Centre (DLR); University of Munich; Helmholtz Association; Karlsruhe Institute of Technology; Helmholtz Association; Karlsruhe Institute of Technology; Charles University Prague
推荐引用方式 GB/T 7714	Loeffel, Sheena,Eichinger, Roland,Garny, Hella,et al. The impact of sulfur hexafluoride (SF6) sinks on age of air climatologies and trends[J],2022,22(2):19.
APA	Loeffel, Sheena.,Eichinger, Roland.,Garny, Hella.,Reddmann, Thomas.,Fritsch, Frauke.,...&Haenel, Florian.(2022).The impact of sulfur hexafluoride (SF6) sinks on age of air climatologies and trends.ATMOSPHERIC CHEMISTRY AND PHYSICS,22(2),19.
MLA	Loeffel, Sheena,et al."The impact of sulfur hexafluoride (SF6) sinks on age of air climatologies and trends".ATMOSPHERIC CHEMISTRY AND PHYSICS 22.2(2022):19.