Evaluation of the profile and the resistance method for estimation of surface fluxes of momentum, sensible and latent heat

Abstract

Hourly lysimetric and micrometeorological data taken over a grass surface at the Meteorological Research Unit, Cardington U.K. have been analysed. A temperature difference and measurements of wind speed at only one height, combined with an independently estimated effective roughness length allowed sensible heat and momentum fluxes determination by the profile method on an hourly basis. The estimates are compared with direct measurements of sensible heat and friction velocity obtained by the eddy correlation method. The sensible and latent heat fluxes are also modelled by the resistance method. Equations based on the Monin-Obukhov similarity theory are used to account for stability effects through various forms of parameterization Aerodynamic and surface resistances, necessary for the Penman-Monteith equation are calculated from routinely measured meteorological data. The profile method for estimation of sensible heat flux and friction velocity is found to work excellently on the discussed daytime experimental data which correspond mainly to near neutral or slightly unstable conditions. Surface latent and sensible heat fluxes can also be described very well by the resistance method. A slightly better estimate of the sensible heat flux is achieved when stability corrections are taken into account. On the contrary Penman-Monteith equation for estimating latent heat flux is insensitive to adjustments for atmospheric stability. The comparison of the various methods leads to the establishment of empirical relationships which correlate various quantities such as soil heat flux, resistances, evapotranspiration etc. to routinely measured meteorological data. © 1992 Springer-Verlag