Consequences of Uncertainties in CO2 Density for Estimating Net Ecosystem CO2 Exchange by Open-path Eddy Covariance
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Errors in the estimation of CO2 surface exchange by open-path eddy covariance, introduced during the removal of density terms [Webb et al. Quart J Roy Meteorol Soc 106:85–100, (1980) - WPL], can happen both because of errors in energy fluxes [Liu et al. Boundary-Layer Meteorol 120:65–85, (2006)] but also because of inaccuracies in other terms included in the density corrections, most notably due to measurements of absolute CO2 density (ρ c ). Equations are derived to examine the propagation of all errors through the WPL algorithm. For an open-path eddy covariance system operating in the Sierra de Gádor in south-east Spain, examples are presented of the inability of an unattended, open-path infrared gas analyzer (IRGA) to reliably report ρ c and the need for additional instrumentation to determine calibration corrections. A sensitivity analysis shows that relatively large and systematic errors in net ecosystem exchange (NEE) can result from uncertainties in ρ c in a semi-arid climate with large sensible heat fluxes (H s ) and (wet) mineral deposition. When ρc is underestimated by 5% due to lens contamination, this implies a 13% overestimation of monthly CO2 uptake.
KeywordsDensity correction Eddy covariance Error propagation Open-path infrared gas analyzer
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- Collaud Coen M, Weingartner E, Schaub D, Hueglin C, Corrigan C, Henning S, Schwikowski M and Baltensperger U (2004). Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis. Atmos Chem Phys 4: 2465–2480 CrossRefGoogle Scholar
- (1899). Rains of sand, dust and mud. Mon Wea Rev 17: 158 Google Scholar
- Falge E, Baldocchi DD, Olson R, Anthoni PM, Aubinet M, Bernhofer C, Burba G, Ceulemans R, Clement R, Dolman AJ, Granier A, Gross P, Grünwald T, Hollinger D, Jensen NO, Katul GG, Keronen P, Kowalski AS, Lai CT, Law BE, Meyers TP, Moncrieff JB, Moors EJ, Munger JW, Pilegaard K, Rannik ü, Rebmann C, Suyker AE, Tenhunen JD, Tu K, Verma SB, Vesala T, Wilson KB and Wofsy SC (2001). Gap filling strategies for defensible annual sums of net ecosystem exchange. Agric Forest Meteorol 107: 43–69 CrossRefGoogle Scholar
- Li-Cor I (2002) Section 2. Theory and operation. In: Li-Cor I (ed) Open path CO2/H2O analyzer. Instruction manual. LI-COR, Lincoln, NebraskaGoogle Scholar
- Penzar I, Poje D (1999–2000) Review of meteorological research in Croatia. Survey of situation up to 1997. Geofizika 16–17:1–32Google Scholar
- Queralt- Mitjans I, Domingo F and Sole-Benet A (1993). The Influence of local sources of the mineral content of bulk deposition over an altitudinal gradient in Filabres Range (SE Spain). J Geophys Res 98: 16761–16768 Google Scholar