Modelling Sea Surface Wind Vectors with Coherent Dual Polarization Synthetic Aperture Radar

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Canada is a maritime nation, whose economy and general well-being is closely tied to the sea. The sea ice in Canada's Arctic continues to reach annual minima that exceed historical levels, increasing ship traffic and resource exploitation, as well as extending the iceberg season in eastern Canada. Massive cruise ships are starting to ply the waters of the Northwest Passage and Baffin Bay exposing northern communities to new economic opportunities. Yet, global warming, which has created these ice-free conditions, has also led to extreme weather, which increases the risks of maritime operations in the North.The overall objective of this research is to improve Canada's capability of monitoring the wind field in Canada's north, including the channels between the Arctic islands, and the waters between Greenland and Newfoundland.An imaging radar is the perfect instrument for gathering information over Canada's northern waters as it is capable of imaging night or day and in all weather, including thick clouds. Imaging radar can transmit and receive microwaves at certain polarizations, like polarizing sunglasses can block out light reflected from the water that has a certain polarization. The Canadian Space Agency is preparing to launch a new generation of imaging radar satellites, called the Radarsat Constellation Mission or RCM. These new satellites will be able to transmit one polarization, and create one image, at the same polarization that was transmitted, plus a second image at the exact opposite polarization. This is called dual-polarization.In this research I will explore the use of dual-polarized radar images of the sea to create maps of wind speed and direction. To do this I will look at the intensity of the energy in each image, and I will combine this with the Doppler frequency in each image. The Doppler effect is the change in frequency of a wave that is received by a moving receiver. You hear this effect when a fire engine drives past you - it is a high pitched sound as it approaches, and a lower pitched sound as it drives away. As the radar approaches a patch of sea surface it is at a higher frequency, and as it flies past the frequency gets lower. This situation gets more complicated as the receiver moves, e.g. if the fire engine is driving towards you as you are riding your bike. The frequency on approach is even higher and gets even lower as the radar passes by. This effect is predictable (and different for each polarization), and is related to the movement of the sea surface, and in turn to both the wind speed and direction, which is what I will estimate.