Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2003
Publication Date: 7/1/2003
Citation: Njoku, E., Jackson, T.J., Lakshmi, V., Chane, T., Nghiem, S. 2003. Soil Moisture Retrieval from AMSR-E. IEEE Transactions on Geoscience and Remote Sensing. 2003. 41:215-229. Interpretive Summary: An algorithm for deriving soil moisture from data produced by the Advanced Microwave Scanning Radiometer on the National Aeronautics and Space Administration Aqua satellite was developed. This new satellite instrument will provide unique new opportunities to acquire soil moisture information on a long-term basis from space. Here the modeling, retrieval, and validation approaches applicable to estimation of soil moisture from the sensor are reviewed. The validation program developed for the instrument will provide for the first time an evaluation of C-band soil moisture estimation capabilities on a continental scale, and an assessment of the ability to estimate soil moisture in light to moderately vegetated areas. The acquisition of extensive ground truth information, combined with hydrologic modeling, will be key to understanding and reducing the microwave model and retrieval uncertainties caused by vegetation and roughness effects at satellite footprint scales to obtain a more reliable product. These results will contribute to the potential operational implementation of this technique in hydrologic, climate and agricultural applications.
Technical Abstract: The Advanced Microwave Scanning Radiometer on the National Aeronautics and Space Administration Aqua satellite will acquire dual-polarized measurements at six frequencies in the range 6.9 to 89 GHz with near-global revisit in 2 days or less. This instrument will provide a significantly improved soil moisture sensing capability over previous spaceborne radiometers due to the combination of low frequency and higher spatial resolution. The soil moisture retrieval utilizes primarily the 6.9 and 10.6 GHz channels to minimize the effects of atmospheric and vegetative attenuation, in an approach that also seeks to minimize the requirement for ancillary data inputs. The algorithm and implementation are described in this paper. A post-launch validation program is planned that will evaluate the accuracy of the soil moisture retrievals and enhance hydrologic applications of the data. Key issues in the evaluation of the soil moisture estimates include identification of the effects of topography, snow cover, precipitation, and forests, and assessment of errors caused by variability in surface temperature, vegetation water content, penetration depth, and spatial heterogeneity.