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Assessment with Controlled In-Situ Data of the Dependence of L-Band Radiometry on Sea-Ice Thickness
摘要： The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) and the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) missions are providing brightness temperature measurements at 1.4 GHz (L-band) for about 10 and 4 years respectively. One of the new areas of geophysical exploitation of L-band radiometry is on thin (i.e., less than 1 m) Sea Ice Thickness (SIT), for which theoretical and empirical retrieval methods have been proposed. However, a comprehensive validation of SIT products has been hindered by the lack of suitable ground truth. The in-situ SIT datasets most commonly used for validation are affected by one important limitation: They are available mainly during late winter and spring months, when sea ice is fully developed and the thickness probability density function is wider than for autumn ice and less representative at the satellite spatial resolution. Using Upward Looking Sonar (ULS) data from the Woods Hole Oceanographic Institution (WHOI), acquired all year round, permits overcoming the mentioned limitation, thus improving the characterization of the L-band brightness temperature response to changes in thin SIT. State-of-the-art satellite SIT products and the Cumulative Freezing Degree Days (CFDD) model are veri?ed against the ULS ground truth. The results show that the L-band SIT can be meaningfully retrieved up to 0.6 m, although the signal starts to saturate at 0.3 m. In contrast, despite the simplicity of the CFDD model, its predicted SIT values correlate very well with the ULS in-situ data during the sea ice growth season. The comparison between the CFDD SIT and the current L-band SIT products shows that both the sea ice concentration and the season are fundamental factors in?uencing the quality of the thickness retrieval from L-band satellites.
关键词： sea ice thickness,retrieval model validation,upward looking sonar,Arctic,Soil Moisture Active Passive (SMAP),Soil Moisture and Ocean Salinity (SMOS) mission,L-band radiometry
更新于2025-09-23 15:19:57
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Near-Real Time Detection of the Re-Opening of the Weddell Polynya, Antarctica, from Spaceborne Infrared Imagery
摘要： A hole in the Antarctic sea ice cover, the Weddell Polynya, unexpectedly re-opened in winter 2017 for the first time since 1976. Models suggest that the polynya opened because warm oceanic water moved up to the surface, melting the ice from below. Here three temperature thresholds applied to near-hourly spaceborne infrared imagery (AVHRR) successfully detect the appearance of a warm spot up to five days before the polynya opened in June and September 2017. Traditional sea ice concentration and thickness criteria could only detect the polynya once it was open. An automatised warning system, using near-real time passive monitoring of warm spots, would allow researchers to reroute vessels or autonomous sensors in order to finally study the polynya as a whole when it opens again, from its preconditioning to its impacts on the climate system.
关键词： AVHRR,infrared imagery,Weddell Polynya,sea ice concentration,sea ice thickness,Antarctic sea ice
更新于2025-09-10 09:29:36