Calculation of ground temperature and fluxes by surface models: a comparison with experimental data in the African savannah

Abstract

In large-scale models, an accurate calculation of energy fluxes at the lower boundary is important to ensure satisfactory predictions of the meteorological parameters. This work is performed using surface models.

In this paper. various surface models. previously studied by Deardorff are tested against experimental data from the West African Monsoon Experiment 1979 in the Ivory Coast. Physical properties of the soil are assumed constant and uniform. Input variables are dry and wet bulb temperatures. wind velocity at the 2 m level, and global radiation. We compute sensible and latent heat fluxes and the surface conduction flux. A Crank-Nicholson scheme has been used with a time step of 5 min. Estimated sensible and latent heat fluxes agree well with experimental data. The order of magnitude of the difference between theoretical and experimental values is 30 W m^-2 for evaporation and 20 W m^-2 for sensible heat. Surface soil heat flux ie less satisfactorily calculated. which could result from properties assumed constant such as soil surface humidity. A model including the heat conduction in the soil provides the best results. The others, based on empirical formulations of surface soil heat flux, are less satisfactory. However. with a simple two-layer model. the predictions are quite acceptable.