HF radar remote sensing of the marginal ice zone and other interesting places

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• Stuart Anderson, University of Adelaide
• Tuesday 01 November 2022, 14:00-15:00
• https://ukri.zoom.us/j/91008981392;BAS Seminar Room 330b.

If you have a question about this talk, please contact Dr. Shenjie Zhou.

The proliferation of HF radars, both skywave and surface wave, has galvanised a search for new environmental observables. Traditionally used for ocean surveillance and mapping of surface currents and wave height, HF ‘over-the-horizon’ radars can now provide data of such resolution and dynamic range that the echoes from the ocean surface can be interrogated for more subtle geophysical signatures. In some instances, first generation theory was developed long ago, in the hope that one day the technology would render the measurement objective achievable. In others, even the first generation theories are only now being developed. The key to implementing this expanded palette of radar missions lies not only with the hardware and signal processing techniques; it depends overwhelmingly on the availability of high fidelity models of the phenomena of interest, with commensurate attention paid to the external factors that govern signal degradation during propagation, and to the electromagnetic scattering theories that are used to map from the geophysical state variables to the radar echoes. A related issue is the consideration of specific geographical circumstances, and how these impact on radar design. There have been several HF radar deployments that achieved far less than was possible because insufficient care was taken to model the operating environment and optimise the radar design accordingly. One particular class of prospective observables embraces those that characterise ice-covered seas, such as ice type, thickness, growth rate and composition. HF radars have very poor spatial resolution when compared with their microwave counterparts but possess exquisite Doppler sensitivity; it follows that the path to any practical ice monitoring and analysis capability lies in the exploitation of the ice surface dynamics as it moves in response to forcing by ocean waves that penetrate the ice field. To this end, we have generalised the HF scattering theory to incorporate the ice type dependence of the dispersion relation of propagating waves in the ice zone. Using this theory, we are able to model the radar signatures of arbitrary ice scenarios, explore the dependence on key parameters, develop optimum measurement strategies and so on. What remains to be completed is the retrieval of the ice parameters from observations. This nonlinear inverse problem is now being addressed using a new optimisation technique. In this talk I shall describe these developments, along with other new remote sensing prospects.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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