Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns
<p>In this paper we develop a CryoSat-2 algorithm to retrieve the surface elevation of the air–snow interface over Antarctic sea ice. This algorithm utilizes a two-layer physical model that accounts for scattering from a snow layer atop sea ice as well as scattering from below the snow surface...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/13/861/2019/tc-13-861-2019.pdf |
| _version_ | 1819278034532827136 |
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| author | S. W. Fons S. W. Fons S. W. Fons N. T. Kurtz |
| author_facet | S. W. Fons S. W. Fons S. W. Fons N. T. Kurtz |
| author_sort | S. W. Fons |
| collection | DOAJ |
| description | <p>In this paper we develop a CryoSat-2 algorithm to retrieve
the surface elevation of the air–snow interface over Antarctic sea ice. This algorithm
utilizes a two-layer physical model that accounts for scattering from a snow layer atop
sea ice as well as scattering from below the snow surface. The model produces waveforms
that are fit to CryoSat-2 level 1B data through a bounded trust region least-squares
fitting process. These fit waveforms are then used to track the air–snow interface and
retrieve the surface elevation at each point along the CryoSat-2 ground track, from which
the snow freeboard is computed. To validate this algorithm, we compare retrieved surface
elevation measurements and snow surface radar return power levels with those from
Operation IceBridge, which flew along a contemporaneous CryoSat-2 orbit in October 2011
and November 2012. Average elevation differences (standard deviations) along the flight
lines (IceBridge Airborne Topographic Mapper, ATM – CryoSat-2) are found to be 0.016 cm
(29.24 cm) in 2011 and 2.58 cm (26.65 cm) in 2012. The spatial distribution of monthly
average pan-Antarctic snow freeboard found using this method is similar to what was
observed from NASA's Ice, Cloud, and land Elevation Satellite (ICESat), where the
difference (standard deviation) between October 2011–2017 CryoSat-2 mean snow freeboard
and spring 2003–2007 mean freeboard from ICESat is 1.92 cm (9.23 cm). While our
results suggest that this physical model and waveform fitting method can be used to
retrieve snow freeboard from CryoSat-2, allowing for the potential to join laser and
radar altimetry data records in the Antarctic, larger (<span class="inline-formula">∼30</span> cm) regional
differences from ICESat and along-track differences from ATM do exist, suggesting the
need for future improvements to the method. Snow–ice interface elevation retrieval is
also explored as a potential to obtain snow depth measurements. However, it is found that
this retrieval method often tracks a strong scattering layer within the snow layer
instead of the actual snow–ice interface, leading to an overestimation of ice freeboard
and an underestimation of snow depth in much of the Southern Ocean but with promising
results in areas such as the East Antarctic sector.</p> |
| first_indexed | 2024-12-24T00:05:35Z |
| format | Article |
| id | doaj.art-6bcf9a2aaea244559950a2dbc6f5d192 |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-12-24T00:05:35Z |
| publishDate | 2019-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-6bcf9a2aaea244559950a2dbc6f5d1922022-12-21T17:25:00ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242019-03-011386187810.5194/tc-13-861-2019Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returnsS. W. Fons0S. W. Fons1S. W. Fons2N. T. Kurtz3Department of Atmospheric and Oceanic Sciences, University of Maryland, College Park, Maryland, USAEarth System Science Interdisciplinary Center (ESSIC), University of Maryland, College Park, Maryland, USACryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USACryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA<p>In this paper we develop a CryoSat-2 algorithm to retrieve the surface elevation of the air–snow interface over Antarctic sea ice. This algorithm utilizes a two-layer physical model that accounts for scattering from a snow layer atop sea ice as well as scattering from below the snow surface. The model produces waveforms that are fit to CryoSat-2 level 1B data through a bounded trust region least-squares fitting process. These fit waveforms are then used to track the air–snow interface and retrieve the surface elevation at each point along the CryoSat-2 ground track, from which the snow freeboard is computed. To validate this algorithm, we compare retrieved surface elevation measurements and snow surface radar return power levels with those from Operation IceBridge, which flew along a contemporaneous CryoSat-2 orbit in October 2011 and November 2012. Average elevation differences (standard deviations) along the flight lines (IceBridge Airborne Topographic Mapper, ATM – CryoSat-2) are found to be 0.016 cm (29.24 cm) in 2011 and 2.58 cm (26.65 cm) in 2012. The spatial distribution of monthly average pan-Antarctic snow freeboard found using this method is similar to what was observed from NASA's Ice, Cloud, and land Elevation Satellite (ICESat), where the difference (standard deviation) between October 2011–2017 CryoSat-2 mean snow freeboard and spring 2003–2007 mean freeboard from ICESat is 1.92 cm (9.23 cm). While our results suggest that this physical model and waveform fitting method can be used to retrieve snow freeboard from CryoSat-2, allowing for the potential to join laser and radar altimetry data records in the Antarctic, larger (<span class="inline-formula">∼30</span> cm) regional differences from ICESat and along-track differences from ATM do exist, suggesting the need for future improvements to the method. Snow–ice interface elevation retrieval is also explored as a potential to obtain snow depth measurements. However, it is found that this retrieval method often tracks a strong scattering layer within the snow layer instead of the actual snow–ice interface, leading to an overestimation of ice freeboard and an underestimation of snow depth in much of the Southern Ocean but with promising results in areas such as the East Antarctic sector.</p>https://www.the-cryosphere.net/13/861/2019/tc-13-861-2019.pdf |
| spellingShingle | S. W. Fons S. W. Fons S. W. Fons N. T. Kurtz Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns The Cryosphere |
| title | Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns |
| title_full | Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns |
| title_fullStr | Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns |
| title_full_unstemmed | Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns |
| title_short | Retrieval of snow freeboard of Antarctic sea ice using waveform fitting of CryoSat-2 returns |
| title_sort | retrieval of snow freeboard of antarctic sea ice using waveform fitting of cryosat 2 returns |
| url | https://www.the-cryosphere.net/13/861/2019/tc-13-861-2019.pdf |
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