Angular and Frequency Correlation for Sea-Ice Thickness Retrieval
Abstract — A combined spatial and frequency domain interferometer or angular and frequency correlation (ACF/FCF) between two radar beams in the VHF-band is applied for the direct measurement of sea-ice thickness. This measurement is critical because the thickness of sea ice within the polar region i...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.329.4803 http://www.ee.washington.edu/research/ersl/Documents/Conference/2004 ACF_FCF_Seaice, IGARSS.pdf |
| Summary: | Abstract — A combined spatial and frequency domain interferometer or angular and frequency correlation (ACF/FCF) between two radar beams in the VHF-band is applied for the direct measurement of sea-ice thickness. This measurement is critical because the thickness of sea ice within the polar region indicates the state of ocean circulation and the associated air–sea heat exchange, which profoundly affects the global heat balance and ocean thermohaline circulation. This new instrument technology— cryospheric advanced sensor (CAS)—can measure sea-ice thickness, filling a critical gap in measuring the polar region. In this paper, we present the algorithm development and demonstration by simulations of estimating the height of the sea-ice that led to the robust design of CAS interferometric system. Sea-ice thickness is derived from the interferometric phase of the ACF/FCF function of two VHF-bandscattered returns of two radar waves that have different frequencies, incident angles, and observation angles. The inversion calculation to estimate the ice thickness is based on several methods, gradientdescent (GD), least-square (LSQ) method, and genetic algorithm (GA). Compared with a GD method, and LSQ method, GA does not require the knowledge of the derivative of the ACF/FCF function. Good agreement is shown with GD and LSQ results, when a single unknown variable—sea-ice thickness—is to be determined. To support the inversion calculations and analysis, we developed an analytical model. The analytical model used to formulate the ACF/FCF function depends on the age of the ice being measured. The analytical model for first-year ice is based on the small perturbation method (presented here) and, for multiyear ice, the Kirchhoff approximation (presented in accompanying paper by the authors). Index Terms—Correlation function, sea ice thickness, rough surface scattering. I. |
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