Scintillometry integrated surface sensible and latent heat fluxes over a young pine stand

In order to further our understanding of surface fluxes at the regional scale, it is necessary to use satellite and numerical model data. However such data must be validated by ground measurements. For this eddy correlation measurement systems are traditionally used. These measurements are rather limited in their footprint (surface of influence) compared with typical pixel surfaces and model grid sizes (several kms).

One promising method, at least for sensible and latent heat surface fluxes measurements, is the use of scintillometry. In recent years this method has been shown to be robust for the estimation of sensible heat flues using optical (0.93µm) Large Aperture Scintillometers (Lagouarde et al 2002, DeBruin 2002) over scales ranging from several hundreds of meters to several kilometers (compatible with the aforementioned satellite and numerical data). On the other hand, the use of scintillometry for the estimation of latent heat fluxes (prototype microwave scintillometers ,27 GHz) is rather more difficult and results related to measurements over vegetation in the literature remain limited (Green 2001, Meijninger 2002).

In order to evaluate the scintillometer method for latent heat fluxes we setup a dual scintillometer experiment, one optical (Univ. of Wageningen) and the other microwave (prototype Univ. of Eindhoven), over a young homogenous maritime pine forest (height 2-3m), installing the instruments at 8.5m with a trajectory of 550m in the southwest of France. The homogeneous short trajectory was chosen, as it is both compatible with reference eddy correlation measurements on site (Gill R3, Licor 7500) and microwave propagation constraints.

Results from the 2009 measurement campaign, several months, will be presented, where preliminary results confirm the robustness of the method for sensible heat fluxes. As for the estimation of latent heat fluxes, the flux estimation would appear to be more complicated. Both sensible and latent heat fluxes will be presented with a particular attention to the latent heat fluxes and the role of the temperature-humidity correlation in the estimation by scintillometry.