Derivation of fluxes from profiles over a moderately homogeneous forest

Measurements of fluxes and profiles of wind and temperature are performed in the roughness layer of a moderately homogeneous forest location. We investigate to what extent vertical scalar fluxes can be derived from profile measurements. The influence of inhomogeneities in the upwind terrain is investigated with footprint analysis and with an inhomogeneous surface-layer model. Four methods to estimate displacement height are suggested, among them is a method involving the structure parameter of the vertical wind. All methods give a decrease of displacement height with increasing wind speed, while roughness length is found to increase with increasing wind speed. For near-neutral conditions dimensionless temperature gradients are found to be substantially lower than the surface-layer values found in the literature for homogeneous terrain with low vegetation. Dimensionless shear however is comparable with the surface-layer value. The height of the roughness layer is 20 times the roughness length. Two schemes with locally derived surface parameters are tested to derive friction velocity and sensible heat flux from the profile measurements. These site specific schemes perform satisfactorily. A third scheme based on surface parameters chosen a priori from the literature performs significantly worse especially for low wind speed and unstable cases.