SMOPS - Algorithm Description
SMOPS was developed to retrieve surface soil moisture from currently available low-frequency microwave satellite sensors, such as the Advanced Microwave Scanning Radiometer (AMSR-E) on the NASA Aqua satellite, for applications in numerical weather and seasonal climate prediction models at National Centers for Environmental Prediction (NCEP). The retrieval algorithm used in SMOPS is the Single Channel Retrieval (SCR) algorithm (Jackson, 1993). Note: The SCR algorithm is not used for ASCAT and SMOS retrievals.
The SMOPS also merges soil moisture retrievals from other satellite sensors, such as ASCAT and SMOS, into its final global product to extend the spatial and temporal coverage. In version 1.0, the baseline satellite was switched to use the WindSat on Naval Research Lab's Coriolis Satellite after ASMR-E failed. In version 2.0, the AMSR-2 onboard GCOM-W1 is used as the baseline satellite sensor. In addition, the SCR algorithm is also applied to near-real time SMOS data to improve the time latency of SMOS soil moisture retrieval.
SMOPS generates two sets of global soil moisture data products: Daily Gridded Product and 6 Hour Gridded Product. Each product contains a blended soil moisture product that merges all soil moisture retrievals at each grid surface, and also individual soil moisture retrievals from the baseline satellite sensor and other available satellite sensors. The daily product contains all soil moisture retrievals available during the past 24 hours while the 6 Hour product includes all soil moisture retrievals available during the past 6 hours.
The details of the SCR algorithm, the sensitivity and the error budget of the algorithm, and the merging method can be found in the Algorithm Theoretical Basis Document.