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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D10301, doi:10.1029/2006JD008190, 2007

Retrieval of average CO2 fluxes by combining in situ CO2 measurements and backscatter lidar information

Fabien Gibert

Institut Pierre Simon Laplace, Laboratoire de Météorologie Dynamique, Ecole Polytechnique, Palaiseau, Cedex, France


Martina Schmidt

Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement, UMR CEA/CNRS 1572, Gif-sur-Yvette, Cedex, France


Juan Cuesta

Institut Pierre Simon Laplace, Laboratoire de Météorologie Dynamique, Ecole Polytechnique, Palaiseau, Cedex, France


Philippe Ciais

Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement, UMR CEA/CNRS 1572, Gif-sur-Yvette, Cedex, France


Michel Ramonet

Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement, UMR CEA/CNRS 1572, Gif-sur-Yvette, Cedex, France


Irène Xueref

Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement, UMR CEA/CNRS 1572, Gif-sur-Yvette, Cedex, France


Eric Larmanou

INRA Unité Mixte de Recherche INRA/INAPG “Environnement et Grandes Cultures”, Thiverval-Grignon, France


Pierre Henri Flamant

Institut Pierre Simon Laplace, Laboratoire de Météorologie Dynamique, Ecole Polytechnique, Palaiseau, Cedex, France


Abstract

The present paper deals with a boundary layer budgeting method which makes use of observations from various in situ and remote sensing instruments to infer regional average net ecosystem exchange (NEE) of CO2. Measurements of CO2 within and above the atmospheric boundary layer (ABL) by in situ sensors, in conjunction with a precise knowledge of the change in ABL height by lidar and radiosoundings, enable to infer diurnal and seasonal NEE variations. Near-ground in situ CO measurements are used to discriminate natural and anthropogenic contributions of CO2 diurnal variations in the ABL. The method yields mean NEE that amounts to 5 μmol m−2 s−1 during the night and −20 μmol m−2 s−1 in the middle of the day between May and July. A good agreement is found with the expected NEE accounting for a mixed wheat field and forest area during winter season, representative of the mesoscale ecosystems in the Paris area according to the trajectory of an air column crossing the landscape. Daytime NEE is seen to follow the vegetation growth and the change in the ratio diffuse/direct radiation. The CO2 vertical mixing flux during the rise of the atmospheric boundary layer is also estimated and seems to be the main cause of the large decrease of CO2 mixing ratio in the morning. The outcomes on CO2 flux estimate are compared to eddy-covariance measurements on a barley field. The importance of various sources of error and uncertainty on the retrieval is discussed. These errors are estimated to be less than 15%; the main error resulted from anthropogenic emissions.

Received 27 October 2006; accepted 1 February 2007; published 16 May 2007.

Keywords: Carbon dioxide; flux retrieval; lidar.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions (0426, 1610); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry.

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Citation: Gibert, F., M. Schmidt, J. Cuesta, P. Ciais, M. Ramonet, I. Xueref, E. Larmanou, and P. H. Flamant (2007), Retrieval of average CO2 fluxes by combining in situ CO2 measurements and backscatter lidar information, J. Geophys. Res., 112, D10301, doi:10.1029/2006JD008190.