STUDY ON THE RELATION OF INTERNAL WAVE VELOCITY TO WATER DEPTH AND MIXED LAYER DEPTH IN THE SOUTH CHINA SEA USING SATELLITE IMAGES

Abstract

Oceanic internal waves (IWs) are often generated at the boundary of stratified water layer of different densities and propagated along a pycnocline where the water density changes rapidly retaining their waveform. Since microwave does not penetrate into water, it is not capable of directly imaging underwater phenomena. However, they can be imaged indirectly by observing their manifestation of the sea surface. Study on the relation of IW velocity to water depth and mixed layer depth (MLD) is important and can improve our understanding of IWs where in-situ two-dimensional measurements are difficult to make. In this study, MODIS/Terra and ENVISAT/ASAR were used to obtain sequential images of IWs in the South China Sea for estimating velocities of IWs. The Hybrid Coordinate Ocean Model (HYCOM) data was used for ocean data to examine the factors that affect the IW velocities. The results show that the velocities estimated by the multi-temporal images are much larger than that by the tidal period method with a single image, and that the reason for the difference is due to the velocity dependence on water depth as IWs travel over long distance between data acquisition times. Further, the MLD was estimated using the two-layer finite depth model consisting of IW velocity and wavelength and compared with HYCOM data. Detailed results will be reported at the conference.enetrate into water, it is not capable of directly imaging underwater phenomena. However, they can be imaged indirectly by observing their manifestation of the sea surface. Study on the relation of IW velocity to water depth and mixed layer depth (MLD) is important and can improve our understanding of IWs where in-situ two-dimensional measurements are difficult to make. In this study, MODIS/Terra and ENVISAT/ASAR were used to obtain sequential images of IWs in the South China Sea for estimating velocities of IWs. The Hybrid Coordinate Ocean Model (HYCOM) data was used for ocean data to examine the factors that affect the IW velocities. The results show that the velocities estimated by the multi-temporal images are much larger than that by the tidal period method with a single image, and that the reason for the difference is due to the velocity dependence on water depth as IWs travel over long distance between data acquisition times. Further, the MLD was estimated using the two-layer finite depth model consisting of IW velocity and wavelength and compared with HYCOM data. Detailed results will be reported at the conference.