Atmos. Chem. Phys. Discuss., 8, 1549-1588, 2008
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
A framework for comparing remotely sensed and in-situ CO2 concentrations
R. Macatangay1,2, T. Warneke1, C. Gerbig2, S. Körner2, R. Ahmadov2, M. Heimann2, and J. Notholt1
1Institute of Environmental Physics, University of Bremen, Bremen, Germany
2Max Planck Institute for Biogeochemistry, Jena, Germany

Abstract. A framework that allows validating CO2 column averaged volume mixing ratios (VMRs) retrieved from ground-based solar absorption measurements using Fourier transform infrared spectrometry (FTS) against measurements made in-situ (such as from aircrafts and tall towers) has been developed. Since in-situ measurements are done frequently and at high accuracy on the global calibration scale, linking this scale with FTS total column retrievals ultimately provides a calibration scale for remote sensing. FTS, tower and aircraft data were analyzed from measurements during the CarboEurope Regional Experiment Strategy (CERES) from May to June 2005 in Biscarrosse, France. Carbon dioxide VMRs from the MetAir Dimona aircraft, the TM3 global transport model and Observations of the Middle Stratosphere (OMS) balloon based experiments were combined and integrated to compare with FTS measurements. The comparison agrees fairly well with differences resulting from the spatial variability of CO2 around the FTS as measured by the aircraft. Additionally, the Stochastic Time Inverted Lagrangian Transport (STILT) model served as a "transfer standard" between the in-situ data measured at a co-located tower and the remotely sensed data from the FTS. The variability of carbon dioxide VMRs was modeled well by STILT with differences coming partly from uncertainties in the spatial variation of carbon dioxide.

Citation: Macatangay, R., Warneke, T., Gerbig, C., Körner, S., Ahmadov, R., Heimann, M., and Notholt, J.: A framework for comparing remotely sensed and in-situ CO2 concentrations, Atmos. Chem. Phys. Discuss., 8, 1549-1588, doi:10.5194/acpd-8-1549-2008, 2008.
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