INHOMOGENEITY OF THE LAND-SURFACE AND PROBLEMS IN THE PARAMETERIZATION OF SURFACE FLUXES IN NATURAL CONDITIONS

Eddy correlation techniques to determine the turbulent fluxes of heat, moisture and momentum in the near-surface atmospheric layer rely on t he Monin-Obukhov similarity theory, which requires stationarity and ho rizontal homogeneity. Experiments at specially selected sites over lan d and particularly over sea are used to develop this concept. Recent e xperiments, deliberately conducted in non-ideal conditions, show an un derestimation of turbulent fluxes. Results from the field experiments FIFE, KUREX, TARTEX and SADE, point to a relationship between the unde restimation of turbulent fluxes and terrain inhomogeneity. In order to systematically correct for this effect a scheme is suggested which us es fetch lengths of different types of surface in the sites surroundin g the environment. In addition, horizontal differences in atmospheric stability above different surfaces are included in the correction sche me. This scheme might be useful for the design of validation experimen ts in non-homogeneous terrain.