Internal wave refraction observed from sequential satellite images

Synthetic aperture radar (SAR) sensors aboard polar-orbiting satellites have the abilities to acquire high spatial resolution images of the Earth's surface under all weather conditions, but their temporal sampling intervals are long. However, currently two SAR sensors aboard the European remote sensing satellite-2 (ERS-2) and the environment satellite (ENVISAT) have almost the same flight paths with ERS-2 following ENVISAT by approximately 28 minutes. Thus, high spatial resolution images from these two SAR can be jointly used to achieve a high temporal sampling interval for ocean feature monitoring and tracking. This approach has been used to track internal wave refraction along Dong-Sha Atoll in the South China Sea (SCS) on 16 April 2003. On that same day, the moderate resolution imaging spectro-radiometer (MODIS) aboard Terra passed though the same location 28 minutes after ERS-2 and collected data under almost no cloud condition. Therefore, Terra MODIS images provide another source for monitoring the wave refraction and validating the internal wave speed around Dong-Sha Atoll.