Retrieval and Validation of Total Seasonal Liquid Water Amounts in the Percolation Zone of Greenland Ice Sheet Using L-band Radiometry

This repository contains the dataset associated with the analyses presented in the following study:

Hossan, A., Colliander, A., Vandecrux, B., Schlegel, N.-J., Harper, J., Marshall, S., and Miller, J. Z.: Retrieval and validation of total seasonal liquid water amounts in the percolation zone of the Greenland Ice Sheet using L-band radiometry, The Cryosphere, 19, 4237–4258, https://doi.org/10.5194/tc-19-4237-2025, 2025.

In this study, we demonstrated the capability of NASA's Soil Moisture Active Passive (SMAP) L-band radiometer to estimate surface and subsurface liquid water amounts (LWA) in the percolation zone of the Greenland Ice Sheet. The article presents our initial retrieval algorithm, validation results, and highlights the potential for developing a Greenland-wide LWA data product.

Contents of this Repository

This repository includes:

• SMAP-retrieved daily, vertically integrated LWA gridded initial data products (2015–2023), derived from enhanced-resolution SMAP TB observations. These data include spatial coordinates, acquisition dates, and a melt flag indicator.
• SMAP_LWA_time_series_AWS contains daily time series at a AWS location (point observation)
• Samimi_EBM_LWA_time_series_AWS contains corresponding time series of LWA estimated by Samimi model forced by PROMICE AWS.
• GEMB_LWA_time_series_AWS contains corresponding time series of LWA estimated by GEMB model forced by PROMICE AWS
• The locations and name ID of the AWS are given in AWS.txt/xls file
• L_band_LWA_yyyy.nc files contain daily LWA and TB data over the entire percolation zone
• Corresponding vertically polarized brightness temperature (TBV) data, including their winter mean and standard deviation.
• Model-based LWA estimates used for validation, including outputs from:
• The locally calibrated Energy and Mass Balance (EMB) model.
• The Glacier Energy and Mass Balance (GEMB) model within NASA’s Ice-sheet and Sea-level System Model (ISSM).

Retrieval and Validation Codebase

The MATLAB scripts and tools used for the microwave retrieval algorithm, radiative transfer modeling, inversion process, and comparative validation with in situ AWS-driven model outputs are available at the following GitHub repository:

🔗 https://github.com/HossanAlamgir/SMAP_MWA_Retrieval_and_Validation_GrIS
(Last accessed: 17 September 2025)

The codebase includes:

• Preprocessing routines for SMAP TB data.
• Implementation of the radiative transfer forward model.
• Inversion and threshold-based detection algorithms.
• Validation scripts for comparison against AWS-forced EMB and GEMB model outputs.

Relevance

These data and methods support ongoing efforts to improve surface mass balance (SMB) estimates and enhance projections of Greenland’s contribution to global sea level rise.