气候变化领域集成服务门户(CCPortal): Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem

CCPortal

DOI	10.5194/acp-19-4041-2019
	Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem
	Schaller C.; Kittler F.; Foken T.; Göckede M.
发表日期	2019
ISSN	16807316
起始页码	4041
结束页码	4059
卷号	19 期号:6
英文摘要	Methane (CH4) emissions from biogenic sources, such as Arctic permafrost wetlands, are associated with large uncertainties because of the high variability of fluxes in both space and time. This variability poses a challenge to monitoring CH4 fluxes with the eddy covariance (EC) technique, because this approach requires stationary signals from spatially homogeneous sources. Episodic outbursts of CH4 emissions, i.e. triggered by spontaneous outgassing of bubbles or venting of methane-rich air from lower levels due to shifts in atmospheric conditions, are particularly challenging to quantify. Such events typically last for only a few minutes, which is much shorter than the common averaging interval for EC (30 min). The steady-state assumption is jeopardised, which potentially leads to a non-negligible bias in the CH4 flux. Based on data from Chersky, NE Siberia, we tested and evaluated a flux calculation method based on wavelet analysis, which, in contrast to regular EC data processing, does not require steady-state conditions and is allowed to obtain fluxes over averaging periods as short as 1 min. Statistics on meteorological conditions before, during, and after the detected events revealed that it is atmospheric mixing that triggered such events rather than CH4 emission from the soil. By investigating individual events in more detail, we identified a potential influence of various mesoscale processes like gravity waves, low-level jets, weather fronts passing the site, and cold-air advection from a nearby mountain ridge as the dominating processes. The occurrence of extreme CH4 flux events over the summer season followed a seasonal course with a maximum in early August, which is strongly correlated with the maximum soil temperature. Overall, our findings demonstrate that wavelet analysis is a powerful method for resolving highly variable flux events on the order of minutes, and can therefore support the evaluation of EC flux data quality under non-steady-state conditions. © 2019. This work is distributed under the Creative Commons Attribution 4.0 License.
语种	英语
scopus关键词	arctic environment; biogenic emission; cold air; eddy covariance; methane; mixing; permafrost; wavelet analysis; wetland; Siberia
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/144534
作者单位	Department of Micrometeorology, University of Bayreuth, Bayreuth, 95440, Germany; Max-Planck-Institute for Biogeochemistry, Jena, 07745, Germany; University of Bayreuth, Bayreuth Center of Ecology and Environmental Research (BayCEER), Bayreuth, 95440, Germany; University of Munster, Institute of Landscape Ecology, Climatology Research Group, Heisenbergstr. 2, Munster, 48149, Germany
推荐引用方式 GB/T 7714	Schaller C.,Kittler F.,Foken T.,et al. Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem[J],2019,19(6).
APA	Schaller C.,Kittler F.,Foken T.,&Göckede M..(2019).Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem.Atmospheric Chemistry and Physics,19(6).
MLA	Schaller C.,et al."Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem".Atmospheric Chemistry and Physics 19.6(2019).