Measured microwave emission and scattering in vegetation canopies

Reflecting metal screens were placed beneath vegetation of three types to allow measurement of the brightness temperature of the vegetation cover alone. A two-frequency radiometer (wavelengths: 11.1 and 5.88 cm) was used to measure the emission from the vegetation, nod a theoretical model involving a loss term and a scattering albedo was fitted to the measured temperatures. Passive and active microwave measurements were also made on fields immediately adjacent to the “screened” fields. Emission and backscattering were measured for these fields under two conditions: 1) with full vegetation cover, and 2) with vegetation removed. Using the same theoretical model and the calculated values for absorption and scattering derived from the screened fields, the effect of the vegetation cover on the soil emission was predicted. The predicted full-canopy temperatures were then compared to those measured. The values for loss and scattering in the vegetation canopy were used in another model to predict the effect of vegetation on backscattering from the soil surface. Again, the predicted backscattering from the vegetation canopy was compared with the measured values of σ°.