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An Alternative Approach for CO_2 Flux Correction Caused by Heat and Water Vapour Transfer

Liu, Heping (2005) An Alternative Approach for CO_2 Flux Correction Caused by Heat and Water Vapour Transfer. Boundary-Layer Meteorology, 115 (1). pp. 151-168. ISSN 0006-8314. doi:10.1007/s10546-004-2420-5.

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Energy and CO_2 fluxes are commonly measured above plant canopies using an eddy covariance system that consists of a three-dimensional sonic anemometer and an H_2O/CO_2 infrared gas analyzer. By assuming that the dry air is conserved and inducing mean vertical velocity, Webb et al. (Quart. J. Roy. Meteorol. Soc. 106, 85-100, 1980) obtained two equations to account for density effects due to heat and water vapour transfer on H_2O/CO_2 fluxes. In this paper, directly starting with physical consideration of air-parcel expansion/compression, we derive two alternative equations to correct for these effects that do not require the assumption that dry air is conserved and the use of the mean vertical velocity. We then applied these equations to eddy flux observations from a black spruce forest in interior Alaska during the summer of 2002. In this ecosystem, the equations developed here led to increased estimates of CO_2 uptake by the vegetation during the day (up to about 20%), and decreased estimates of CO_2 respiration by the ecosystem during the night (approximately 4%) as compared with estimates obtained using the Webb et al. approach.

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Alternate Title:An Alternative Approach for CO2 Flux Correction Caused by Heat and Water Vapour Transfer
Additional Information:© Springer 2005. (Received in final form 29 July 2004) I am grateful for advice and input from J.T. Randerson in the analysis and writing stages of this manuscript. I am also grateful for the internal reviews of William J Massman (USDA) who also checked the derivation procedure step-by-step and encouraged me to obtain the three-dimensional form of my equation. Thanks are given to Tapio Schneider (Caltech), Zhonghua Yang (Caltech) and Xuhui Lee (Yale) for their useful discussions and comments. Constructive comments from referees are greatly appreciated. Thanks are due to Jamie Lindfors for field work. This work was supported by Grants NSF OPP-0097439. Additional support from the Davidow research fund at Caltech is gratefully acknowledged.
Funding AgencyGrant Number
Davidow Discovery FundUNSPECIFIED
Subject Keywords:Air-parcel expansion/compression, Carbon flux, Eddy covariance, Flux correction, Open path CO_2/H_2O infrared gas analyzers
Issue or Number:1
Record Number:CaltechAUTHORS:20170409-071622351
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Official Citation:Liu, H. Boundary-Layer Meteorol (2005) 115: 151.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76431
Deposited By: 1Science Import
Deposited On:03 Apr 2018 20:36
Last Modified:15 Nov 2021 16:59

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