High-quality eddy-covariance CO2 budgets under cold climate conditions

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Kittler , F , Eugster , W , Foken , T , Heimann , M , Kolle , O & Göckede , M 2017 , ' High-quality eddy-covariance CO2 budgets under cold climate conditions ' , Journal of Geophysical Research : Biogeosciences , vol. 122 , no. 8 , pp. 2064-2084 . https://doi.org/10.1002/2017JG003830

Title: High-quality eddy-covariance CO2 budgets under cold climate conditions
Author: Kittler, Fanny; Eugster, Werner; Foken, Thomas; Heimann, Martin; Kolle, Olaf; Göckede, Mathias
Contributor organization: Department of Physics
INAR Physics
Date: 2017-08
Language: eng
Number of pages: 21
Belongs to series: Journal of Geophysical Research : Biogeosciences
ISSN: 2169-8953
DOI: https://doi.org/10.1002/2017JG003830
URI: http://hdl.handle.net/10138/307196
Abstract: This study aimed at quantifying potential negative effects of instrument heating to improve eddy-covariance flux data quality in cold environments. Our overarching objective was to minimize heating-related bias in annual CO2 budgets from an Arctic permafrost system. We used continuous eddy-covariance measurements covering three full years within an Arctic permafrost ecosystem with parallel sonic anemometers operation with activated heating and without heating as well as parallel operation of open- and closed-path gas analyzers, the latter serving as a reference. Our results demonstrate that the sonic anemometer heating has a direct effect on temperature measurements while the turbulent wind field is not affected. As a consequence, fluxes of sensible heat are increased by an average 5 W m(-2) with activated heating, while no direct effect on other scalar fluxes was observed. However, the biased measurements in sensible heat fluxes can have an indirect effect on the CO2 fluxes in case they are used as input for a density-flux WPL correction of an open-path gas analyzer. Evaluating the self-heating effect of the open-path gas analyzer by comparing CO2 flux measurements between open- and closed-path gas analyzers, we found systematically higher CO2 uptake recorded with the open-path sensor, leading to a cumulative annual offset of 96 g Cm-2, which was not only the result of the cold winter season but also due to substantial self-heating effects during summer. With an inclined sensor mounting, only a fraction of the self-heating correction for vertically mounted instruments is required.
114 Physical sciences
1172 Environmental sciences
Peer reviewed: Yes
Rights: cc_by_nc_sa
Usage restriction: openAccess
Self-archived version: publishedVersion

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