20 Jul 2021

20 Jul 2021

Review status: this preprint is currently under review for the journal TC.

A leading-edge based method for correction of slope-induced errors in ice-sheet heights derived from radar altimetry

Weiran Li, Cornelis Slobbe, and Stef Lhermitte Weiran Li et al.
  • Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, The Netherlands

Abstract. Satellite radar altimetry has been an important tool for cryospheric applications such as measuring ice-sheet height or assessing snow/ice anomalies (e.g., the extensive melt in Greenland in 2012). Although accurate height measurements are key for such applications, slope-induced errors due to undulating topography within the kilometre-wide pulse-limited footprint can cause multi-meter errors. Therefore different correction methods have been developed ranging from the slope method to the point-based method. Each of these methods have shortcomings as they either neglect the actual topography or the actual footprint that can be estimated by a combination of the leading edge and topography. Therefore, a novel Leading Edge Point-Based (LEPTA) method is presented that corrects for the slope-induced error by including the leading edge information of the radar waveform to determine the impact point. The principle of the method is that only the points on the ground that are within range determined by the begin and end of the leading edge are used to determine the impact point.

Benchmarking of the LEPTA method to the slope- and point-based method based on CryoSat-2 LRM acquisitions over Greenland in 2019 shows that heights obtained by LEPTA outperform the other methods when compared to ICESat-2 observations, both in the flat, interior regions of Greenland and in regions with more complex topography. The median difference between the slope-corrected CryoSat-2 and the ICESat-2 heights is almost negligible, whereas the other methods can have a 0.22 m and 0.69 m difference, and the Level-2 data provided by ESA have a 0.01 m difference. The median absolute deviation, which we use as an indicator of the variation of errors, is also the lowest in LEPTA (0.09 m) in comparison to the aforementioned methods (0.22 m and 0.13 m) and ESA Level-2 data (0.15 m). Based on that, we recommend considering LEPTA to obtain accurate height measurements with radar altimetry data, especially in regions with complex topography.

Weiran Li et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of 'A leading-edge based method for correction of slope-induced errors in ice-sheet heights derived from radar altimetry', by W. Li et al.', Anonymous Referee #1, 18 Aug 2021
    • AC1: 'Reply on RC1', Weiran Li, 03 Dec 2021
  • RC2: 'Comment on tc-2021-176', Anonymous Referee #2, 10 Oct 2021
    • AC2: 'Reply on RC2', Weiran Li, 03 Dec 2021

Weiran Li et al.

Weiran Li et al.


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Short summary
This study proposes a new method for correcting the slope-induced errors in satellite radar altimetry. The slope-induced errors can largely affect the height estimations of ice sheets, if left uncorrected. This study applies the method to radar altimetry data (CryoSat-2), and compares the performance with two existing methods.The performance is assessed by comparing with independent height measurements from ICESat-2. The assessment shows that the method has promising performance.