Relevance of time-varying and time-invariant retrieval error sources on the utility of spaceborne soil moisture products

Errors in remotely-sensed soil moisture retrievals originate from a combination of time-invariant and time-varying sources. For land modeling applications such as forecast initialization, some of the impact of time-invariant sources can be removed given known differences between observed and modeled soil moisture climatologies. Nevertheless, the distinction is seldom made when evaluating remotely-sensed soil moisture products. Here we describe an Observing System Simulation Experiment (OSSE) for radiometer-only soil moisture products derived from the NASA Hydrosphere States ( Hydros) mission where the impact of time-invariant errors is explicitly removed via the linear rescaling of retrievals. OSSE results for the 575,000 km(2) Red-Arkansas River Basin indicate that climatological rescaling may significantly reduce the perceived magnitude of Hydros soil moisture retrieval errors and expands the geographic areas over which retrievals demonstrate value for land surface modeling applications.