Snow wetness retrieved from close-range L-band radiometry in the western Greenland ablation zone

Close-range (CR) L-band radiometry and quasi-simultaneous in situ snow characterizations were conducted in May 2019 at the Swiss Camp research site in the ablation zone of the western Greenland ice sheet. Snow liquid-water and its melt/refreeze are retrieved from microwave antenna temperatures measured with the ground-based L-band radiometer ELBARA-III. The emission model (EM) used in the retrieval is a two-layer configuration of the 'L-Band Specific Microwave Emission Model of Layered Snowpack'. Consistent snow wetness retrievals were achieved from both single- and multi-angle CR observations of L-band antenna temperatures. This suggests that multi-angle observation is not a pre-requisite for snow wetness retrieval. Therefore, in addition to soil moisture and ocean salinity (SMOS) multi-angle measurements, snow wetness can be estimated from spaceborne L-band brightness temperatures measured at a single observation angle, such as from NASA's SMAP satellite. Our results provide partial validation of a recently presented snow wetness retrieval approach based on the same EM and applied over Greenland using multi-angle SMOS brightness temperatures. Agreement between measured CR antenna temperatures and SMOS brightness temperatures is found to be within the 95% confidence intervals of ELBARA-III and SMOS measurement uncertainties. Our measurements confirm the modeled response of antenna temperatures to diurnal variations of snow wetness.

Automated summary

Close-range L-band radiometry and in situ snow characterizations were conducted in Greenland, showing consistent snow wetness retrievals from single- and multi-angle observations and validating a previously proposed retrieval approach using multi-angle SMOS brightness temperatures. The measured CR antenna temperatures were found to agree with SMOS brightness temperatures within the confidence intervals, confirming the modeled response of antenna temperatures to diurnal variations of snow wetness.