气候变化领域集成服务门户(CCPortal): Background heterogeneity and other uncertainties in estimating urban methane flux: Results from the Indianapolis Flux Experiment (INFLUX)

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DOI	10.5194/acp-20-4545-2020
	Background heterogeneity and other uncertainties in estimating urban methane flux: Results from the Indianapolis Flux Experiment (INFLUX)
	V. Balashov N.; J. Davis K.; L. Miles N.; Lauvaux T.; J. Richardson S.; R. Barkley Z.; A. Bonin T.
发表日期	2020
ISSN	1680-7316
起始页码	4545
结束页码	4559
卷号	20 期号:7
英文摘要	As natural gas extraction and use continues to increase, the need to quantify emissions of methane (CH4), a powerful greenhouse gas, has grown. Large discrepancies in Indianapolis CH4 emissions have been observed when comparing inventory, aircraft mass balance, and tower inverse modeling estimates. Four years of continuous CH4 mole fraction observations from a network of nine towers as a part of the Indianapolis Flux Experiment (INFLUX) are utilized to investigate four possible reasons for the abovementioned inconsistencies: (1) differences in definition of the city domain, (2) a highly temporally variable and spatially non-uniform CH4 background, (3) temporal variability in CH4 emissions, and (4) CH4 sources that are not accounted for in the inventory. Reducing the Indianapolis urban domain size to be consistent with the inventory domain size decreases the CH4 emission estimation of the inverse modeling methodology by about 35 %, thereby lessening the discrepancy and bringing total city flux within the error range of one of the two inventories. Nevertheless, the inverse modeling estimate still remains about 91 % higher than inventory estimates. Hourly urban background CH4 mole fractions are shown to be spatially heterogeneous and temporally variable. Variability in background mole fractions observed at any given moment and a single location could be up to about 50 ppb depending on a wind direction but decreases substantially when averaged over multiple days. Statistically significant, long-term biases in background mole fractions of 2-5 ppb are found from single-point observations for most wind directions. Boundary layer budget estimates suggest that Indianapolis CH4 emissions did not change significantly when comparing 2014 to 2016. However, it appears that CH4 emissions may follow a diurnal cycle, with daytime emissions (12:00-16:00 LST) approximately twice as large as nighttime emissions (20:00-05:00 LST). We found no evidence for large CH4 point sources that are otherwise missing from the inventories. The data from the towers confirm that the strongest CH4 source in Indianapolis is South Side landfill. Leaks from the natural gas distribution system that were detected with the tower network appeared localized and non-permanent. Our simple atmospheric budget analyses estimate the magnitude of the diffuse natural gas source to be 70 % higher than inventory estimates, but more comprehensive analyses are needed. Long-term averaging, spatially extensive upwind mole fraction observations, mesoscale atmospheric modeling of the regional emissions environment, and careful treatment of the times of day are recommended for precise and accurate quantification of urban CH4 emissions. © 2020 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	boundary layer; estimation method; heterogeneity; methane; natural gas; uncertainty analysis; urban area; Indiana; Indianapolis; United States
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/141404
作者单位	NASA Postdoctoral Program, Universities Space Research Association, 7178 Columbia Gateway Drive, Columbia, MD 21046, United States; Pennsylvania State University, University Park, PA, United States; NASA Global Modeling and Assimilation Office (GMAO), Goddard Space Flight Center, Greenbelt, MD 20771, United States; Laboratory of Climate Sciences and Environment, Gif-sur-Yvette, France; Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States; Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, United States; Pennsylvania State University, University Park, PA, United States
推荐引用方式 GB/T 7714	V. Balashov N.,J. Davis K.,L. Miles N.,et al. Background heterogeneity and other uncertainties in estimating urban methane flux: Results from the Indianapolis Flux Experiment (INFLUX)[J],2020,20(7).
APA	V. Balashov N..,J. Davis K..,L. Miles N..,Lauvaux T..,J. Richardson S..,...&A. Bonin T..(2020).Background heterogeneity and other uncertainties in estimating urban methane flux: Results from the Indianapolis Flux Experiment (INFLUX).Atmospheric Chemistry and Physics,20(7).
MLA	V. Balashov N.,et al."Background heterogeneity and other uncertainties in estimating urban methane flux: Results from the Indianapolis Flux Experiment (INFLUX)".Atmospheric Chemistry and Physics 20.7(2020).