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Numerical Simulation on Series of Airborne SAR Images of Internal Waves

Li Fei(1), Chong Jinsong(1) and Ouyang Yue(1)

(1) Chinese Academy of Sciences, 19th, the 4th ring road,north, 100080 Beijing, China

Abstract

Internal waves are the most prominent features in the SAR image of coastal waters. Recently numerical simulation of SAR internal wave images has become an effective way to research internal waves. Pierini(1989) developed a weakly two-dimensional RLW equation and took a numerical method to simulate the internal waves of Alboran sea. Peter Brant(1996) used a numerical two-layer model to study the ERS-1/2 internal wave image of the strait of Messina. Lynett(2002) deduced a two-dimensional depth-integrated model and simulated the internal waves propagating through Dongsha island. These simulations took satellites SAR images (such as ERS-1/2, RADARSAT, ENVISAT ASAR, etc) as the validation of the simulation. Airborne SAR can get a series of internal wave images of a fixed area during a period of research time. So we choose the airborne SAR internal wave’s images for the simulation validation.

Most internal waves which appear at the coastal water area are of weakly two-dimensional and weakly nonlinear. The main aim of our simulation is to validate the SAR internal wave imaging mechanism with our airborne SAR internal wave images. Under this condition, we chose the weakly two dimensional RLW equation (Pierini, 1989) as our numerical model. Taking the amplitude information retrieved from the first SAR internal wave image as the initial value of the model, we can get the whole propagating process of internal waves.

Based on the numerical model results, the internal-wave-induced sea surface currents field could be deduced. Submitting the surface currents into hydrodynamic (wave/current interaction) model and the surface wave spectral perturbation theory, the surface wave spectral perturbations induced by internal waves could be found. Finally, by applying the microwave backscatter model and the SAR image model, the SAR image intensity can be acquired.

Then we can get the simulated SAR internal wave images. Through comparing of these simulated images with the real ones we will have a direct recognition of the characteristics of internal wave propagation. Numerical simulation of SAR internal wave image establishes the relationship between the hydrodynamic process and ocean remote sensing image.

Key words: Internal waves, RLW equation, SAR Image simulation

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry