Soil moisture retrieval over the Mackenzie River basin using AMSR-E 6.9 GHz brightness temperature

An approach is proposed to estimate soil moisture and to monitor its change from AMSR-E 6.9 GHz passive microwave data acquired over a large northern basin. The lack of in situ direct measurements is a major issue to be resolved to reach the aim of this work. Therefore, “external” ancillary data were used as a surrogate for available measurements. The methodology is based on the inversion of a microwave radiative transfer model. A sequential method based on the sensitivity of the emitted microwave signal to soil roughness and vegetation parameters was applied to calibrate the model. The roughness parameter was determined from AMSR-E data acquired under dry watershed conditions. The vegetation parameters were estimated under wet conditions. The method was first applied in the Peace-Athabasca Delta area located in Northern Alberta, Canada. The estimated geophysical parameters were then used to retrieve soil moisture estimates for sites with similar LAI values. It was found that the variations of the estimated soil moisture compared well with soil moisture imported from NARR data. A satisfactory agreement was obtained between soil moisture, precipitation and temperature.