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Adjustment of annual NEE and ET for the open-path IRGA self-heating correction: Magnitude and approximation over a range of climate |
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| Authors: | BR Reverter A CarraraA Fernández C GimenoMJ Sanz P Serrano-OrtizEP Sánchez-Cañete A WereF Domingo V RescoGG Burba AS Kowalski |
| Institution: | a Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18071 Granada, Spain b Grupo de Física de la Atmósfera, Centro Andaluz de Medio Ambiente (CEAMA), 18006 Granada, Spain c Fundación Centro de Estudios Ambientales del Mediterráneo - CEAM, Charles R. Darwin 14, 46980 Paterna, Valencia, Spain d Departamento de Desertificación y Geo-ecología, Estación Experimental de Zonas Áridas - CSIC, Ctra. Sacramento s/n, 04120 La cañada de San Urbano, Almería, Spain e Department of Hydrology and Geo-environmental Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands f Centro de Investigación del Fuego, Toledo, 45071, Spain g LI-COR Biosciences, 4421 Superior Street, Lincoln, NE 68540, USA |
| Abstract: | The self-heating correction is known to modify open-path eddy covariance estimates of net ecosystem CO2 exchange, typically towards reduced uptake or enhanced emissions, but with a magnitude heretofore not generally documented. We assess the magnitude of this correction to be of order 1 μmol m−2 s−1 (daytime) for half-hourly fluxes and consistently over 100 g C m−2 for annual integrations, across a tower network (CARBORED-ES) spanning climate zones from Mediterranean temperate to cool alpine. We furthermore examine the sensitivity of the correction to its determining factors. Due to significant diurnal variation, the means of discriminating day versus night can lead to differences of up to several tens of g C m−2 year−1. Since its principal determinants - temperature and wind speed - do not include gas flux data, the annual correction can be estimated using only meteorological data so as to avoid uncertainties introduced when filling gaps in flux data. For fast retro-correction of annual integrations published prior to the recognition of this instrument surface heating effect, the annual impact can be roughly approximated to within 12 g C m−2 year−1 by a linear function of mean annual temperature. These determinations highlight the need for the flux community to reach a consensus regarding the need for and the specific form of this correction. |
| Keywords: | Eddy covariance Open-path Infrared Gas Analyzer Self-heating correction Annual carbon budget Annual water vapor budget |
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