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Internal Waves, Andaman Sea

Internal waves are generated in density stratified waters. They often exhibit highly nonlinear characteristics resembling 'solitons' or 'solitary waves.' In the Andaman Sea, the internal solitary waves are of such extraordinary amplitudes (up to 100 m have been observed) that they affect drill ship operations.

Systematic investigation of internal waves using optical images is not easy since they can be clearly imaged only when there is no cloud cover and under favourable sun elevation angle.

The internal waves modulate the overlying surface waves and the sea surface manifestations of internal waves are readily observed in SAR images. They appear as alternating bright and dark bands corresponding to regions of increased surface roughness (bright) alternating with smooth regions (dark). Often they occur as packets with 4 to 10 bright bands in each packet.

A systematic study of the spatial distribution of the internal solitary waves in the Andaman Sea is being conducted to extract information on their generation and propagation characteristics. Evidence of phase shifts associated with soliton interactions has also been observed in the ERS images. RADARSAT scanSAR images, with their wider spatial coverage, provide additional information as more than two packets can be observed in a single scene.

© ESA 1997 . Internal waves in Andaman sea captured in one pass of ERS-2.
This image suffers from JPEG compression errors.

© ESA 1995 . 3 consecutive ERS Images | © CSA 1997 . RADARSAT Image (ScanSar)