Passive L-band H polarized microwave emission during the corn growth cycle

From a campaign conducted in 2002, hourly L-band H polarized T_B (Brightness temperature) measurements are available for five episodes distributed over the corn growth cycle. In this study, fitting the τ-ω model to the T_B measurements shows that the empirical parameter b, defining the optical depth or canopy opacity (r), and its dependence towards the incidence and azimuth angles both change during the growth cycle. The b found for the early growth stage is about three times larger than expected based on the literature, while near peak biomass and at senescence its value is about half. Moreover, the soil moisture dependence of the roughness and crop row orientation are found to be important uncertainties in the T_B simulations. The latter effect is particularly significant at senescence.