Research On Method For Ocean Surface Currents Measurement With HF Hybrid Sky-surface Wave Radar

Sea surface current is an essential and important ocean dynamic factor. The measurementof currents on large spatial scales, which can be used to observe some dynamic oceanphenomena such as mesoscale eddy, has made a significant contribution to marineenvironmental protection, disaster prevention and damage reduction. As a new detectingmeans, the research on HF radar based on skywave transmission and surface wave reception(hybrid sky-surface wave radar) is in its infancy. And there have not been any report aboutocean surface currents measurement with HF hybrid sky-surface wave radar system. Thisthesis makes a research on methods for ocean surface currents measurement with HF hybridsky-surface wave radar system.(1) According to the geometric construction and the localization theory of the hybridsky-surface wave radar, the Doppler shift and spectrum spread features are analyzed, based onits first-order spectra theory. Theoretical results are in good agreement with the experimentalresults, which provides theory references for the separation of first-order spectra.(2) A new algorithm for the separation of first-order spectra is proposed, which is basedon the characteristic that the amplitude of the first-order spectra is higher. The performance ofthis SNR algorithm is tested by applying it to the measured data. The result indicates that thenew algorithm is better than another algorithm called differential spectrum algorithm. Thefirst-order spectra of hybrid sky-surface wave radar, affected by bistatic angle and ionosphere,shows some different features. So the algorithm should be modulated when applied to themeasured data of hybrid sky-surface wave radar. And the corresponding method is exhibitedin this article.(3) Research on the inversion of sea currents is made based on the digital beam formingtechnology (DBF). A solution of applying instantaneous frequency method (IF) insynthetizing peaks is provided, in terms of more than one peaks existed in Doppler spectrumon some specific azimuth. And the only current velocity can be obtained after this process.(4) Research on the inversion of sea currents is made, based on MUSIC algorithm. Three methods to solve the source number estimation problem is introduced, and one of them isapplied to measured data processing. Analysis of results from the two algorithms isinvestigated, based on the measured data. The comparison indicates that the variationtendencies of radial velocities from MUSIC algorithm and DBF algorithm are similar.