Studying Ocean Internal Waves With SAR

A theory of internal wave SAR imaging has been improved by applying KdV equation, Bragg back scatter model, and replacing surface wave action equation with high frequency ocean wave spectrum balance equation (Yuan yeli,1997) . The problem is escaped successfully by the theory that the signature appearing on SAR image will drop to the unrecognizable level after a few relaxation times. Based on the new theory, the effects of all the parameters including hydrodynamic parameters and radar parameters on the internal waves SAR images are studied. Hydrodynamic parameters include the internal waves amplitude, the depth of thermocline, the difference of water density between upper and down layer. The radar parameters include the radar wave band, the polarity, incidence angle and azimuth direction. By analyzing the effects of environment factors such as wind and surfactant film on the internal waves SAR images, two conclusions can be drawn. The first is that only under some wind conditions, the signature of internal waves can be imaged on the SAR. The second is that under the effect of surfactant film the light and dark bands basis on the hydrodynamic modulation will appear the only dark bands. The dispersion relation of the nonlinear KdV equation is drawn under the two layers model. The importance of the nonlinear in the dispersion relation is emphasized when the hydrodynamic parameters are extracted from the internal waves SAR images. The hydrodynamic modulation theory of radar imaging of internal waves is made up of KdV equation, high frequency ocean wave spectrum balance equation and Bragg back scatter model. Basis on the theory the amplitude of internal waves and the depth of thermocline can be extracted from the internal waves SAR images. The theory results are compared with the data and the differences are little, so the theory can be accepted.