Measurement of Wave Coherence Using Spaceborne Synthetic Aperture Radar

Abstract

Abstract : LONG-TERM GOALS. The Unites States Navy is evaluating the feasibility of constructing and deploying very large mobile offshore bases (MOBs). Such platforms may be 1.5 km long and 300 m wide. These structures fall far outside the scope of typical maritime design experience. Proper design depends upon the ability to characterize ocean waves fields, particular nonlinear features like wave long crestedness and wave groupiness. A long-term goal is to provide such characterizations. OBJECTIVES. The specific objective of this work is to develop and apply techniques for the objective estimation of wave long crestedness and wave groupiness from spaceborne synthetic aperture radar (SAR) data of ocean surface waves. Spaceborne SAR imagery offers the unique combination of high resolution (25 m) and large swath (100 km) necessary to measure large scale wave coherence. APPROACH. The authors listed above are the primary contributors to this work. The basic approach here is two fold. First, develop techniques to objectively measure two properties of wave coherence: ocean wave crest length and long crestedness. Second, apply these techniques to spaceborne SAR imagery. The difference between crest lengths and wave groupiness observed in SAR imagery and those predicted by linear theory is a measure of wave coherence caused by nonlinear wave-wave interaction.