Abstract's details
Capitalizing on the experience of iceberg study from classical, SAR and interferometric altimeter for the CRISTAL mission
Event: 2023 Ocean Surface Topography Science Team Meeting
Session: Science IV: Altimetry for Cryosphere and Hydrology
Presentation type: Type Oral
Contribution: PDF file
Abstract:
As demonstrated by Tournadre et al (2008) small icebergs (<10km²), in fact any target emerging from the sea surface, can easily be detected in open water by high resolution altimeter waveforms analysis . In LRM mode the iceberg signature is a parabola in the waveform space, whilst it reduces to a bright spot in SAR mode . For both signatures, algorithms have been developed to detect and analyze the iceberg's characteristics under hypothesis on the ice backscatter and iceberg freeboard.
In SARIN mode, icebergs can also be detected by analysis of the power waveform. The processing of the interferometric information (phase difference and coherence), i.e. the SARIn swath processing, allows the determination of the topography of the icebergs surface at resolution of the order of the along track resolution (~300m) as well as the iceberg surface backscatter. The SARIn processing allows thus an estimate of the iceberg volume, freeboard and backscatter. The SARIn mode also allows the detection of iceberg within sea ice.
For the CRISTAL mission, Iceberg detection, volume change, and drift have been listed as a priority user requirement. The CRISTAL dual frequency altimeter follows on the CRYOSAT-2 altimeter and can operates in inteferometric mode. This mode is the one that provides the most precise estimates of iceberg volume and freeboards. The planned processing of the CRISTAL SARIn data will include the detection and analysis of icebergs based on the past experience on CRYOSAT-2 SARIn data. The analysis of Cryosat-2 SARin data showed the importance of the correction of the phase difference for the impact of the platform roll angle using the Recchia et al (2017) model. This correction allows to perform the swath processing close to nadir and to estimate small elevation variations.
We present the specific SARIn swath processing and analysis of several Cryosat-2 passes obtained during normal operation and during CRYOSAT-2 roll campaigns showing that swath processing can be used to estimate icebergs characteristics within open sea as well as within sea ice. We also present examples of swath processing over sea ice showing that SARin data could also be used to characterize sea ice leads and to estimate the sea ice freeboards .
Figure : (left) Surface backscatter and (right) elevation (at 300m along track, 50m across track resolution), SARIn swath processing of the roll campaign 7 pass R7-A-C11
~
In SARIN mode, icebergs can also be detected by analysis of the power waveform. The processing of the interferometric information (phase difference and coherence), i.e. the SARIn swath processing, allows the determination of the topography of the icebergs surface at resolution of the order of the along track resolution (~300m) as well as the iceberg surface backscatter. The SARIn processing allows thus an estimate of the iceberg volume, freeboard and backscatter. The SARIn mode also allows the detection of iceberg within sea ice.
For the CRISTAL mission, Iceberg detection, volume change, and drift have been listed as a priority user requirement. The CRISTAL dual frequency altimeter follows on the CRYOSAT-2 altimeter and can operates in inteferometric mode. This mode is the one that provides the most precise estimates of iceberg volume and freeboards. The planned processing of the CRISTAL SARIn data will include the detection and analysis of icebergs based on the past experience on CRYOSAT-2 SARIn data. The analysis of Cryosat-2 SARin data showed the importance of the correction of the phase difference for the impact of the platform roll angle using the Recchia et al (2017) model. This correction allows to perform the swath processing close to nadir and to estimate small elevation variations.
We present the specific SARIn swath processing and analysis of several Cryosat-2 passes obtained during normal operation and during CRYOSAT-2 roll campaigns showing that swath processing can be used to estimate icebergs characteristics within open sea as well as within sea ice. We also present examples of swath processing over sea ice showing that SARin data could also be used to characterize sea ice leads and to estimate the sea ice freeboards .
Figure : (left) Surface backscatter and (right) elevation (at 300m along track, 50m across track resolution), SARIn swath processing of the roll campaign 7 pass R7-A-C11
~
