Measurement of evaporation from bare soil and a new approach to surface resistance

A detailed numerical model incorporating moisture and heat fluxes, which simulates bare soil evaporation together with surface resistance parameter is briefly described here. On the other hand, a now open chamber, which provides reasonably accurate estimate of evaporation, is explained. The uniqueness of this chamber is that it is completely open at its inlet and thereby the effect of chamber on the natural profiles of temperature, humidity and turbulence is minimized. Simulated evaporation rates from an experimental bare plot were compared with the measured rate by the open chamber system. Although the model estimated slightly higher evaporation rates, the diurnal variations show a similar trend. The model is calibrated with the measured and simulated soil moisture of top 0.5 cm layer and a reasonable agreement is found. The simulated surface resistance parameter does not show a proper relation with the soil moisture, but it can be proposed that hysteresis is present in the surface resistance-soil moisture relations.