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Published in Zahrah Naankwat Musa, Satellite-Based Mitigation and Adaptation Scenarios for Sea Level Rise in the Lower Niger Delta, 2018
Available literature show that efforts have been made to develop an empirical relationship between satellites derived surface water extents (including flooded areas) with river stage or discharge. Such a relationship has been established for braided rivers; for non-braided rivers the results have depended on the river system, thus inundation area can increase or decrease with stage. With better SAR missions such as TerraSAR-X- TanDEM-X formation, DEM data with good vertical accuracy are now available for better hydraulic flood modelling. TanDEM- X has 12.5m spatial resolution and produces less than 2m vertical accuracy (DLR, 2015). Although made for polar ice change estimation and monitoring, the high spatial coverage of Cryosat-2 is also being exploited for near-shore mapping and inland water monitoring (Villladsen, Andersen, & Stenseng, 2014). Cryosat-2 which operates in SAR and interferometric modes, has a drifting orbit and therefore (unlike all the other satellites) has little repetitive data (since repeat cycle is 369 days). Its high spatial density coverage makes it good for hydraulic modelling (and all its evaluations have produced good results). With successful use of Cryosat-2 data to obtain river water levels and topography, the use of drifting orbits is being proposed as more suitable for river water surface topography mapping, derivation of river profiles and building of pseudo time series (Bercher1, Calmant, Picot, Seyler, & Fleury, 2014).
Remote Sensing of Sea Ice Hazards
Published in George P. Petropoulos, Tanvir Islam, Remote Sensing of Hydrometeorological Hazards, 2017
Apart from passive microwave and optical satellite imageries, satellite radar altimeters such as CryoSat-2 (Ku-band) have also been used to estimate sea ice volume and thickness (Laxon et al. 2013). Figure 7.3 shows a recent near real-time (NRT) sea ice thickness product (at 5 km grid; also available at 1 km for individual sectors) generated by Centre for Polar Observation and Modelling/European Space Agency (CPOM/ESA) for 2-, 14-, and 28-day time period. Ice thickness is calculated by combining the freeboard measurements and estimates of snow depth and density derived from climatology (Warren et al. 1999; Laxon et al. 2013). NRT data are preliminary fast access products, which ignore all the precise corrections that come with the final products made available 30 days later. As the ice thickness is estimated using the freeboard and ice/snow density, it is able to provide full thickness of the ice (from keel-depth to sail-height). Similar to CryoSat-2 ice thickness, Geoscience Laser Altimeter System (GLAS) instrument (wavelength 1064 nm) onboard ICESat provided ice thickness calculated using freeboard and snow density (Kwok and Cunningham 2008). However, these products were available till 2008. Thus, CryoSat-2 provides one of the best available datasets of ice thickness. This can be tremendously useful in dealing with ice hazards and mitigation plans.
Interferometry
Published in Iain H. Woodhouse, Introduction to Microwave Remote Sensing, 2006
The Cryosat mission is an ESA Earth Explorer Opportunity altimetry mission aimed at determining variations in the thickness of the Earth’s continental ice sheets and marine ice cover. Its primary objective is to test and quantify the prediction of thinning polar ice due to global warming and to do so requires both centimetre accuracies in range but also high spatial resolutions in order to provide altimetric coverage of the steep margins of the ice sheets, and to systematically monitor changes in the thickness of Arctic sea ice. It therefore employs both aperture synthesis in the along-track direction and interferometric processing in the across-track direction by using two antennas 1m apart using an instrument called SIRAL (SAR Interferometric Radar Altimeter). SIRAL is a high-resolution Ku-band (2.2cm) radar altimeter based on the heritage of the French Poseidon instrument from TOPEX/Poseidon and Jason altimeter missions.
A new Arctic MSS model derived from combined Cryosat-2 and ICESat observations
Published in International Journal of Digital Earth, 2022
Guodong Chen, Zhijie Zhang, Stine Kildegaard Rose, Ole Baltazar Andersen, Shengjun Zhang, Taoyong Jin
Cryosat-2 is ESA’s first ice mission to monitor variations in the thickness of the polar sea ice covers and continental ice sheets. It was launched on 8 April 2010 and started its data collection in July 2010, with an altitude of about 717 km and a latitudinal coverage of 88°S-88°N. So far, it has already operated for over 11 years and the data are regularly released by ESA. Since a new type of delay/Doppler radar altimeter, SIRAL, is carried on the satellite, Cryosat-2 can operate in three different modes to cope with different surfaces on Earth: Low-Resolution Mode (LRM) for open ocean and interior ice sheets, Synthetic Aperture Radar (SAR) mode for ice-covered polar oceans and Synthetic Aperture Radar Interferometry (SIN) mode for sloping terrains such as the ice sheet margins. In the ice-covered Arctic Ocean, the Cryosat-2 observations are mainly collected using the SAR mode. In this paper, the processing of SAR mode data is discussed. Two types of Cryosat-2 data products were used in this study: the Level-1b waveform product is used for lead detection and the surface elevation from Level-2 Geophysical Data Record (GDR) is used for sea surface determination. Both products can be downloaded from ESA’s ftpserver (ftp://science-pds.cryosat.esa.int/). When this study started, the current Baseline D CryoSat-2 products were not available, hence Baseline C products are used in our research and the time span of Cryosat-2 data is from July 2010 to March 2019, consisting of 105 months.