Preprints
https://doi.org/10.5194/tc-2022-85
https://doi.org/10.5194/tc-2022-85
 
19 May 2022
19 May 2022
Status: this preprint is currently under review for the journal TC.

The sensitivity of satellite microwave observations to liquid water in the Antarctic snowpack

Ghislain Picard1,2, Marion Leduc-Leballeur3, Alison F. Banwell4, Ludovic Brucker5, and Giovanni Macelloni3 Ghislain Picard et al.
  • 1Univ. Grenoble Alpes, CNRS, Institut des Géosciences de l’Environnement (IGE), UMR 5001, Grenoble, France
  • 2Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, Denmark
  • 3Institute of Applied Physics "Nello Carrara", Sesto Fiorentino, Italy
  • 4Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, USA
  • 5Center for Satellite Applications and Research NOAA/NESDIS and the U.S. National Ice Center, College Park MD, USA

Abstract. Surface melting on the Antarctic Ice Sheet has been monitored by satellite microwave radiometery for over 40 years. Despite this long perspective, our understanding of the microwave emission from wet snow is still limited, preventing the full exploitation of these observations to study supraglacial hydrology. Using the Snow Microwave Radiative Transfer (SMRT) model, this study investigates the sensitivity of microwave brightness temperature to snow liquid water content at frequencies from 1.4 to 37 GHz. We first determine the snowpack properties for 8 selected coastal sites by retrieving profiles of density, grain size and ice layers from microwave observations when the snowpack is dry during winter time. Second, a series of brightness temperature simulations is run with added water. The results show that: i) a small amount of liquid water (≈0.5 kg m-2 can be detected, but the actual amount can not be retrieved in the full range of possible water contents, ii) the detection of a buried wet layer is possible up to a maximum 1 to 6 m depth depending on the frequency (6–37 GHz) and on the site, iii) surface ponds and water-saturated areas may prevent melt detection, but the current coverage of these water bodies in the large satellite field of view is presently too small in Antarctica to have noticeable effects, iv) at 1.4 GHz, while the simulations are less reliable, we found a weaker sensitivity to liquid water and the maximal depth of detection is relatively shallow (<10 m) compared to the typical radiation penetration depth in dry firn (≈1000 m) at this low frequency. These numerical results pave the way for the development of improved multi-frequency algorithms to detect melt intensity and depth in the Antarctic snowpack.

Ghislain Picard et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-85', Anonymous Referee #1, 21 Jun 2022
  • RC2: 'Comment on tc-2022-85', Anonymous Referee #2, 21 Jun 2022
  • RC3: 'Comment on tc-2022-85', Angelika Humbert, 23 Jun 2022

Ghislain Picard et al.

Model code and software

Snow Microwave Radiatiave Transfer Ghislain Picard, Melody Sandells, Henning Löwe https://github.com/smrt-model/smrt

Ghislain Picard et al.

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Short summary
Using a snowpack radiative transfer model, we investigate in which conditions meltwater can be detected from passive microwave satellite observations from 1.4 to 37 GHz. In particular, we determine the minimum detectable liquid water content, the maximum depth of detection of a buried wet snow layer and the risk of false alarm due to supraglacial lakes. These results provide information for the developers of new, more advanced satellite melt products, and for the users of the existing products.