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This paper presents an analysis of regional fluxes obtained with a small aircraft over heterogeneous terrain in the South West of France, during the large scale field experiment CERES'07. We use a method combining variable flight-path segmentation with basic airborne footprint analysis. The segmentation is based on topography, land use and soil type, using a.o. satellite imagery and digital maps. The segments are delineated using an average footprint length, based on all flights, and segment lengths, which are variable in space but not in time. The method results in segment averaged carbon and energy fluxes, which are shown to be representative of regional fluxes. Our analysis is focussed on the carbon dioxide, heat and evaporative fluxes around solar noon. We will show that spatial and seasonal variations in the fluxes can be linked to the underlying landscape. In addition, a comparison between the airborne data and ground flux data is made to support our results. However, due to the incompleteness of ground data for some predominant vegetation types (even in such a data dense context), upscaling of ground data to regional fluxes was not possible. Without the comparison, we are still able to demonstrate that aircraft can provide direct and meaningful estimates of regional fluxes of energy and carbon dioxide. [ABSTRACT FROM AUTHOR]

The paper describes a numerical interpretation of the April 2007 CarboEurope Regional Experiment Strategy (CERES) campaign, devotedto the study of CO2 cycle at the regional scale. The four consecutive clear sky days with intensive observations of CO2 concentration, fluxes at the the surface and in the boundary layer have been simulated with the Meso-NH mesoscale model. Aircraft observations of CO2 have been used to identify surface modelling errors and to calibrate the CO2 components of the surface model. After this calibration, the paper describes a systematic comparison of the model outputs with all the data collected during CERES, in April 2007. As a conclusion, an example of CO2 budgeting from the mesoscale model is given. [ABSTRACT FROM AUTHOR]