Possible use of active microwave remote sensing data for prediction of regional evaporation by Numerical simulation of soil water movement in the unsaturated zone

This paper presents a methodology for estimating bare soil evaporation from microwave radar data. The classical Richards’ equation is solved numerically by using soil moisture values estimated from simulated radar data as the upper boundary condition. It is shown that a sampling period of 3 days for the radar data permits a good estimation of evaporation for a clay soil with relatively low hydraulic conductivity values. However, for a sandy soil with higher hydraulic conductivity values the sampling period must be shorter, particularly for wet conditions which occur after rain events. The possibility of extending the local transfer model to the field scale, matching the expected observed scale from airborne or satellite radar, is investigated. We show that this can be done when the spatial heterogeneities of the field can be scaled through similar media concept.