Lake Ice Thickness Retrieval Method with ICESat-2-Assisted CyroSat-2 Echo Peak Selection

Ye, Hao; Jin, Guowang; Zhang, Hongmin; Xiong, Xin; Li, Jiahao; Wang, Jiajun

doi:10.3390/rs16030546

Cited by 2 publications

(3 citation statements)

References 29 publications

(46 reference statements)

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“…The typical LIT uncertainty obtained with the SAR_LIT retracker is of the order of 5 cm, when the ice is well established on the lake, representing a significant improvement with respect to previous studies (as e.g. [7][8][9][10][11]). As expected, LIT estimates are of significantly higher accuracy, by a factor of 2 to 3 better, when using Sentinel-6 UFSAR data at 20 Hz in contrast to LRM data due to increased resolution.…”

Section: Discussionmentioning

confidence: 70%

“…In this paper, we focus on the analysis and modeling of high resolution radar waveforms data (UFSAR and FFSAR) over ice-covered lakes, with the aim of exploiting the double peak signature to obtain robust LIT estimates of higher accuracy compared to those retrieved from LRM data and in previous studies that make use of empirical methods (as e.g. [7][8][9][10]).…”

Section: Lake Ice Thickness Signature In Sar Radar Echograms and Wave...mentioning

confidence: 99%

“…[7] showed the potential of estimating LIT from the varying peak separation, linked to the ice growth, of Cryosat-2 Ku-band Synthetic Aperture Radar (SAR) waveforms, but achieving RMSE values ranging from 20 cm to 41 cm when compared to in situ measurements from Great Slave Lake and Great Bear Lake, Canada. More recently, [8] proposed to improve this approach by using ICESat-2 data to increase the accuracy of the Cryosat-2 peak selection, obtaining LIT estimates with a RMSE of 0.14 cm when compared to field measurements. It is worth noting here that assessing the accuracy of satellite-based LIT retrievals by using in situ measurements can be somewhat misleading as these are usually collected operationally near the shore of the lakes, while the satellite ground track segments used for the LIT estimates are taken over the lakes, the furthest away from the shore to avoid land contamination.…”

Section: Introductionmentioning

confidence: 99%

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Improving the Estimation of Lake Ice Thickness with High Resolution Radar Altimetry Data

Mangilli,

Duguay,

Murfitt

et al. 2024

Preprint

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Lake ice thickness (LIT) is a sensitive indicator of climate change identified as a thematic variable of Lakes as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). Here, we present a novel and efficient analytically based retracking approach for estimating LIT from high-resolution Ku-band (13.6 GHz) synthetic aperture radar (SAR) altimetry data. The retracker method is based on the analytical modeling of the SAR radar echoes over ice-covered lakes that show a characteristic double-peak feature attributed to the reflection of the Ku-band radar waves at the snow-ice and ice-water interfaces. The method is applied to Sentinel-6 Unfocused SAR (UFSAR) and Fully Focused SAR (FFSAR) data, with their corresponding tailored waveform model, referred to as the SAR_LITand FFSAR_LITretracker, respectively. LIT retrievals from Sentinel-6 SAR data at different posting rates are evaluated against those obtained from thermodynamic lake ice model simulations and Low Resolution Mode (LRM) Sentinel-6 and Jason-3 data over two ice seasons during the tandem phase of the two satellites, allowing precise assessment of the continuity between LRM and SAR LIT retrievals. Consistency checks of the Sentinel-6 SAR LIT estimates are also performed using optical/radar images that provide information on the snow/ice conditions on the same dates. The analysis is performed on Great Slave Lake and Baker Lake (Canada) that differ in terms of lake size, bathymetry, snow/ice properties, and seasonal evolution of LIT. The accuracy of the LIT estimates with the SAR LIT retrackers is on the order of 5 cm once the ice is well established on the lakes, meeting the GCOS requirements of LIT measurement uncertainty, which is a factor of 2 to 3 times better than that of LIT obtained with LRM data, bringing a further improvement compared to previous analyses and methods. The SAR LIT retrackers presented are promising tools for monitoring the inter-annual variability and trends in LIT from current and future SAR altimetry missions.

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Section: Discussionmentioning

confidence: 70%

Section: Lake Ice Thickness Signature In Sar Radar Echograms and Wave...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Improving the Estimation of Lake Ice Thickness with High Resolution Radar Altimetry Data

Mangilli,

Duguay,

Murfitt

et al. 2024

Preprint

View full text Add to dashboard Cite

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Improving the Estimation of Lake Ice Thickness with High-Resolution Radar Altimetry Data

Mangilli,

Duguay,

Murfitt

et al. 2024

Remote Sensing

View full text Add to dashboard Cite

Lake ice thickness (LIT) is a sensitive indicator of climate change, identified as a thematic variable of Lakes as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). Here, we present a novel and efficient analytically based retracking approach for estimating LIT from high-resolution Ku-band (13.6 GHz) synthetic-aperture radar (SAR) altimetry data. The retracker method is based on the analytical modeling of the SAR radar echoes over ice-covered lakes that show a characteristic double-peak feature attributed to the reflection of the Ku-band radar waves at the snow–ice and ice–water interfaces. The method is applied to Sentinel-6 Unfocused SAR (UFSAR) and Fully Focused SAR (FFSAR) data, with their corresponding tailored waveform model, referred to as the SAR_LIT and FFSAR_LIT retracker, respectively. We found that LIT retrievals from Sentinel-6 high-resolution SAR data at different posting rates are fully consistent with the LIT estimations obtained from thermodynamic lake ice model simulations and from low-resolution mode (LRM) Sentinel-6 and Jason-3 data over two ice seasons during the tandem phase of the two satellites, demonstrating the continuity between LRM and SAR LIT retrievals. By comparing the Sentinel-6 SAR LIT estimates to optical/radar images, we found that the Sentinel-6 LIT measurements are fully consistent with the evolution of the lake surface conditions, accurately capturing the seasonal transitions of ice formation and melt. The uncertainty in the LIT estimates obtained with Sentinel-6 UFSAR data at 20 Hz is in the order of 5 cm, meeting the GCOS requirements for LIT measurements. This uncertainty is significantly smaller, by a factor of 2 to 3 times, than the uncertainty obtained with LRM data. The FFSAR processing at 140 Hz provides even better LIT estimates, with 20% smaller uncertainties. The LIT retracker analysis performed on data at the higher posting rate (140 Hz) shows increased performance in comparison to the 20 Hz data, especially during the melt transition period, due to the increased statistics. The LIT analysis has been performed over two representative lakes, Great Slave Lake and Baker Lake (Canada), demonstrating that the results are robust and hold for lake targets that differ in terms of size, bathymetry, snow/ice properties, and seasonal evolution of LIT. The SAR LIT retrackers presented are promising tools for monitoring the inter-annual variability and trends in LIT from current and future SAR altimetry missions.

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Lake Ice Thickness Retrieval Method with ICESat-2-Assisted CyroSat-2 Echo Peak Selection

Cited by 2 publications

References 29 publications

Improving the Estimation of Lake Ice Thickness with High Resolution Radar Altimetry Data

Improving the Estimation of Lake Ice Thickness with High Resolution Radar Altimetry Data

Improving the Estimation of Lake Ice Thickness with High-Resolution Radar Altimetry Data

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