Inhomogeneity of the Land Surface and Problems in theParameterization of Surface Fluxes in Natural Conditions

Summary Eddy correlation techniques to determine the turbulent fluxes of heat, moisture and momentum in the near-surface atmospheric layer rely on the Monin-Obukhov similarity theory, which requires stationarity and horizontal homogeneity. Experiments at specially selected sites over land and particularly over sea are used to develop this concept. Recent experiments, deliberately conducted in non-ideal conditions, show an underestimation of turbulent fluxes. Results from the field experiments FIFE, KUREX, TARTEX and SADE, point to a relationship between the underestimation of turbulent fluxes and terrain inhomogeneity. In order to systematically correct for this effect a scheme is suggested which uses fetch lengths of different types of surface in the sites surrounding the environment. In addition, horizontal differences in atmospheric stability above different surfaces are included in the correction scheme. This scheme might be useful for the design of validation experiments in non-homogeneous terrain. Received April 9, 1997 Revised July 16, 1997