Impact of Aggregation Rules of Ancillary Parameters on Soil Moisture Retrievals from Space-borne Microwave Radiometer Observations

Retrieving soil moisture from space-borne microwave radiometer observations often requires ancillary parameters such as surface vegetation opacity and roughness. The conventional approach for deriving representative values of these parameters is usually to simply average the corresponding parameters of high resolution pixels over the whole microwave sensor footprint. This paper uses a microwave emission model (MEM) to demonstrate that the aggregation rules significantly impact the results and if chosen correctly can reduce the soil moisture retrieval errors from the single-channel retrieval and the MEM inversion algorithms.