Sensible Heat Flux Estimated from Routine Meteorological Data by the Resistance Method

Abstract

A method is described for evaluation of hourly values of the sensible heat flux from routine meteorological data. Use is made of the energy balance at the surface and of the Monteith-Penman formula for estimation of the latent heat flux. The soil heat flux is modelled as a given fraction of the sensible heat flux. The net radiation is computed from the information on cloudiness and solar elevation. A model for surface resistance for evaporation is presented. It is shown that the surface resistance correlates well with the atmospheric humidity deficit. Furthermore, the surface resistance is related to net radiation and to accumulated net radiation since last precipitation. The accumulated net radiation determines the degree of dryness of the soil. The model results of surface resistance and sensible heat flux are compared with experimental data from three sites: Høbakkegaard, Denmark; Marsta, Sweden; and Cabauw, Holland. The comparison is satisfactory and encourages the use of the method for routine determination of these surface parameters. The potential evaporation model, in general, strongly overestimates the rate of evaporation. Somewhat better results are obtained with the equilibrium model, but still the evaporation is overestimated for very dry weather conditions. Use of the surface resistance model for evaluation of hourly values of the latent heat flux gives very good agreement with experimental results.