Ocean Dynamic Parameters Inversion And Application Method With High Frequency Surface Wave Radar

During the last decades serveral radio wave detection systems working on different frequency bands have become useful tools for remote sensing research based on the electromagnetic scattering theory. As one kind of HF over-the-horizon radar, high frequency surface wave radar(HFSWR) in ocean remote sensing working on ground wave propagation mode takes advantage of low attenuation characteristic of high frequency electromagnetic waves (3MHz to30MHz) propagating across the ocean surface to measure the horizontal ocean dynamic parameters such as current, wind and wave, and also can monitor ship, airplane and iceberg. Vertical polarization antennas are used to transmit the electromagnetic waves. HFSWR is capable of all-weather remote sensing of large area ocean surface dynamics with relatively high precision, not influenced by adverse weather, based on which it has become one of the most important remote sensing tools for ocean information monitoring integration network.Radio Oceanography Laboratory of Wuhan University has developed short-range, middle-range, long-range HFSWR, portable HFSWR and multiple frequency HFSWR supported by Chinese High-Technology research and development program(863Plan Project) from1987in China. Till now the capability of currents detection has been considered satisfying the requirements for routine marine observations while wind and wave detection accuracy cannot satisfy the matched status. The Twelfth-Five-Year Chinese High-Technology863Plan Project under grant2012AA091701(Distribution HF Over the Horizon Radar Network Theory and Technology)under development is aim to solve wind and wave detection problem. In the plan, sky wave propagation mode, surface wave propagation mode, sky-surface wave combination propagation mode and bistatic detection mode are all take into consideration to realize in short-range sophisticated observation and long-range covered observation. This work studies ocean dynamic parameters inversion from HFSWR, wind, wave and shallow water depth included, and introduces some primary results using current, wind wave detected by HFSWR to support ocean engineering application. The details in this research are presented as follows.1.Firstly, the empireical models of wave and wind inversion from high frequency surface wave radar are proposed in this paper. Some modifications are introduced into the Barrick’s model of significant waveheight inversion to improve its performances under the affection of noises and interferences and an empirical model of ocean surface wind speed and significant wave height relation is proposed by analysis data obtained by buoy in-situ observations at the coverage of radar beam. To figure out the unknown coefficients in the modified model, we apply the modified model to the significant waveheight calculations from HFSWR field data and then fitting them to the significant waveheight and wind speed results output from a wave buoy located in the radiating coverage of the radar site. The models’parameters are estimated by minimum standard Euclidean norm method from six months’buoy in-situ measuring data and the estimation result shows the model’s stability. The empireical inversion models are applied to monitor wind and wave more than six months and the comparison with that from the buoy shows that the proposed model works with relatively satisfactory accuracy, especially at the period of typhoon Fung-Wong, which confirms the inversion models’validity.2. The Doppler spectra of the HFSWR sea echoes contain ocean wave spectra information. In this paper a Tikhonov regularization method for extracting ocean wave spectral from the Doppler spectra with HFSWR is proposed. The theory and technology of ill-posed problem, regularization and Tikhonov regularization are all introduced. The method is developed by introducing a regularization mathematics model to the discrete linearization integral equation based on the principle of HF radio wave ocean detecting. The resolution of discrete linearization integral equation is obtained by singular value decomposition (SVD) method and the regularization parameter is determined by L-Curve method involved by Hansen. Validity and accuracy of the proposed method are demonstrated by numerical simulation with different noise level both at single radar and two radars of the same coverage detecting which show good agreement:Non-directional spectra can be extracted from single radar and directional spectra can be obtained by two radars at the same coverage. Some preliminary results from measured data detected by HFSWR OSMAR071located at Longhai of Fujian province are also introduced. Further study is needed for the practical use of this method. It’s promising for HFSWR wave inversion in application.3. Ocean surface parameters detection from the HFSWR currently all have assumption that the water depth is deep. At this situation, the Bragg ocean gravity wave phase velocity is independent of water depth and the Doppler frequency is only a function of radio frequency. But in fact, there is shallow water in the ocean which may cause uncertain about the ocean gravity wave phase velocity, especially at the near shore area and inner sublittoral zone closely related with people’s lives. This will influence the accuracy of ocean surface dynamic parameters inversion from HFSWR Facing these difficulties, this paper studies the shallow water detection theory and method with HFSWR and a shallow water depth extraction method is proposed. In this paper, we deduced the theory model of for shallow water depth and vector current inversion from multiple sites high frequency surface wave radar(HFSWR) sea echo. By field data analysis at deep water condition, the ocean gravity wave phase velocity inversion is verified by comparison with theoretical velocity based on deep water dispersion relationship.We verified the proposed shallow water depth inversion method with three and more than three sites, which gives spirit prospects. By analyzing data collected from three HFSWRs detection experiment at Jiangsu north, the inversion results show good performance, which is perspective for extraction ocean water depth and dynamic parameters in inner sublittoral zone and shallow water by HFSWR in engineering application.4. In order to fullfil the HFSWR data enginerring application, the floater trajectory tracking method with wind,wave, current detected by HFSWR is introduced in this paper. A Multi-Frequency high frequency surface wave radar (HFSWR) field experiment was conducted to verify the accuracy of the drifter tracking trajectory at East China Sea. The currents measurement with HFSWR is validated by an Acoustic Doppler Current Profilers(ADCP) in-situ observation. By using Lagrange-tracking method, the drifter on the ocean surface is tracked with currents detected by two Multi-Frequency HFSWR. The tracking drifter trajectory shows good agreement with the GPS records which indicates that drifter tracking by HFSWR is valid. And the main factors, especially the wind speed affecting the tracking accuracy are discussed.