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L-band radiometers are used to retrieve sea surface salinity (SSS) and study the cryosphere. At high latitudes, it is frequent that both sea ice and water are present in the sensor's field of view. Accurately characterizing the scene is crucial for oceanographic and cryospheric applications. We present a model to derive the ice fraction affecting observations by the Aquarius and SMAP radiometers and discuss the impact of different types of ice on observed brightness temperatures. Our model shows improved match between brightness temperatures and ice fraction when compared to the model used previously in the Aquarius products. We will report on the feasibility and expected accuracy for an ice correction algorithm in the SSS retrieval algorithm.

Existing model functions for the dielectric constant of sea water produce viable retrievals of ocean salinity but with differences that are important for eventual optimization of the science product. Issues exist in cold water and the dependence on sea surface temperature. Additional accuracy is needed to resolve the behavior in cold water and a residual bias correlated with sea surface temperature. The model function developed from direct measurements of the dielectric constant highlights the issues and points to regimes where new measurements and accuracy are needed.

SMAP and SMOS have been successfully providing L-band brightness temperature (Tb) since 2015 and 2011, respectively [1, 2]. Since both missions provide Low Earth Orbit observation at the same frequency, inter-calibration of brightness temperatures measured from these two missions leading to a consistent Tb record is critical in order to have consistent and reliable science datasets. For a radiometer, stability testing and drift monitoring of measured brightness temperature are often performed by comparing measured Tb with estimated Tb using in-situ temperature measurement and/or higher frequency microwave observations. Therefore having one additional reference Tb measured by another radiometer will help characterize and calibrate a radiometer with higher accuracy and benefit both missions.