Detection and Characterization of Deep Water Wave Breaking Using Moderate Incidence Angle Microwave Backscatter from the Sea Surface
Abstract
The importance of wave breaking in both microwave remote sensing and air-sea interaction has led to this investigation of the utility of a Ku-Band CW Doppler scatterometer to detect and characterize wave breaking in the open ocean. Field and laboratory measurements by previous authors of microwave backscatter from sharp-crested and breaking waves have shown that these events can exhibit characteristic signatures in moderate incidence angle measurements of the radar cross-section (RCS) and Doppler spectrum. Specifically, breaking events have been associated with polarization independent sea spikes in the RCS accompanied by increasing mean frequency and bandwidth of the Doppler spectrum. The joint statistics of the microwave quantities indicative of breaking are used to investigate detection schemes for breaking events identified from the video recordings. The most successful scheme is based on thresholds in both the RCS and the Doppler bandwidth determined from joint distributions for breaking and non-breaking waves. Microwave events consisting of a sea spike in the RCS accompanied by a large bandwidth are associated with the steep forward face of waves in the early stages of breaking. The sea spike statistics are investigated as functions of wave field parameters and friction velocity u*. For VV and HH polarization, the frequency of sea spike occurrence and the sea spike contribution to the mean RCS show an approximately cubic dependence on u*, which is consistent with theoretical modelling and various measures of whitecap coverage.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1990
- Accession Number
- ADA236732
Entities
People
- Andrew T. Jessup
Organizations
- Woods Hole Oceanographic Institution