Significant wave height retrieval from synthetic radar images

In many offshore activities radar imagery is used to observe and predict ocean waves. An important issue in analyzing the radar images is to resolve the significant wave height. Different from 3DFFT methods that use an estimate related to the square root of the signal-to-noise ratio of radar images, in this paper we present a completely different approach. This approach is based on the intuitive observation that the shadowing of waves leads to a visibility that depends on the distance from the radar. We will show that for irregular waves the visibility depends in a characteristic way on the distance normalized by the peak wavelength, and on the ratio of radar height and significant wave height and only slightly on the details of the wave spectrum. By comparing the visibility of a specific sea with results of Monte Carlo simulations of sea states with various significant wave heights, the best LSM fit then determines the significant wave height. In this paper we restrict to long-crested waves and illustrate the method with various cases.