CRYORAD: A FORWARD MODEL SENSITIVITY STUDY FOR A LOW-FREQUENCY PASSIVE MICROWAVE RADIOMETER (0.4-2 GHZ) OVER ICE SHEETS.

A. Haddjeri¹, G. Picard¹, M. Leduc Leballeur², M. Brogioni³, G. Macelloni³, H. Signargout¹,A. Q. Aurelien Quiquet²

¹ Institut des Geosciences de l’Environnement (IGE), Université Grenoble Alpes / CNRS, UMR 5001, Grenoble, France, ²Laboratoire des Sciences du Climat et de l’Environnement, ³Institute of Applied Physics “N. Carrara ” National Research Council Sesto Fiorentino, Italy

The CryoRad mission, an Earth Explorer 12 candidate, aims to bridge critical observational gaps in understanding the Earth’s cold regions. It plans to deploy a low-frequency wideband microwave radiometer operating from 0.4 to 2 GHz to improve the assessment of ice sheet mass balance and stability. This presentation details a forward model sensitivity study conducted using the Snow Microwave Radiative Transfer (SMRT) model to evaluate the future satellite’s performance and refine mission requirements, with a specific focus on ice sheets.

Our study utilized the SMRT model to simulate the satellite’s response to various geophysical parameters, focusing primarily on ice sheet temperature and density profiles. We performed a series of sensitivity tests to better characterize the response of different ice sheets and to constrain the temperature inversion.

Our simulations confirm that both temperature and density have impact on the microwave signal’s penetration depth, with the signal capable of penetrating to the bottom of the ice sheet. We also observed a clear frequency-dependent contribution to the brightness temperature. Specifically, higher frequencies (2 GHz) are more sensitive to the upper portion of the temperature profile, whereas lower frequencies (0.4 GHz) provide a unique window into the deeper parts of the ice sheet, offering insights into basal temperatures.

Secondly, we investigated the impact of density layering. We collected in-situ density profiles, analyzed their deterministic and stochastic components, and developed a generator to produce realistic density profiles across the ice sheets. We then simulated the impact of this layering on the brightness temperature, initially using an incoherent model and subsequently with a coherent model. This second approach is crucial as previous work has shown that a coherent model is particularly sensitive to density layering at low frequencies [1].

The results of this sensitivity study are essential for assessing the mission’s capability to deliver scientifically useful products related to cold ice sheet properties and confirm CryoRad’s potential to significantly advance our understanding of polar processes in a warming climate.

Reference:

1. M. Leduc-Leballeur et al., “Modeling L-Band Brightness Temperature at Dome C in Antarctica and Comparison With SMOS Observations,” in IEEE Transactions on Geoscience and Remote Sensing, vol. 53, no. 7, pp. 4022-4032, July 2015, doi: 10.1109/TGRS.2015.2388790.