Abstract. Firn aquifers are important in polar ice sheet hydrology and the associated mass and energy transport processes. Although the firn aquifer extent has been mapped using passive microwave satellite observations, models for predicting the L-band brightness temperature time series have remained elusive. This paper implements a radiative transfer model for time series L-Band V and H-pol brightness temperature (TB) observations from the 3 km SMAP enhanced resolution data product. The model relates the firn aquifer permittivity and properties of the dry firn layer above the aquifer to SMAP observations. Results are presented for aquifers within both the Greenland and Antarctic ice sheets. The results show that the brightness temperature is more sensitive to aquifer liquid water content changes when the water table is closer to the surface. The method provides a tool for the radiometry study of firn aquifer and a theoretical basis for potentially retrieving firn aquifer liquid water content using passive microwave data.
Xu et al. (2026) studied this question.