Radar Remote Sensing Estimates of Waves and Wave Forcing at a Tidal Inlet

• Published in: Journal of atmospheric and oceanic technology Vol. 32; no. 4; pp. 842 - 854
• Main Authors: Diaz Mendez, Guillermo M, Haller, Merrick C, Raubenheimer, Britt, Elgar, Steve, Honegger, David A
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.04.2015
• Subjects: Accuracy; Algorithms; Bathymeters; Bathymetry; Energy flux; Energy transfer; Estimates; Genetic transformation; Image acquisition; Inlets; Inlets (waterways); Land acquisition; Mathematical analysis; Offshore; Probability density function; Probability density functions; Probability theory; Radar; Radar cross sections; Radar data; Radiation; Remote sensing; Remote sensing systems; Sensors; Spatial discrimination; Spatial distribution; Spatial resolution; Superhigh frequencies; Surface waves; Tidal inlets; Transformations; Transformations (mathematics); Wave breaking; Wave height; Wave power; X-band; North Carolina; United States > US; New River
• ISSN: 0739-0572; 1520-0426
• DOI: 10.1175/JTECH-D-14-00215.1

The time and space variability of wave transformation through a tidal inlet is investigated with radar remote sensing. The frequency of wave breaking and the net wave breaking dissipation at high spatial resolution is estimated using image sequences acquired with a land-based X-band marine radar. Using the radar intensity data, transformed to normalized radar cross section sigma super(0), the temporal and spatial distributions of wave breaking are identified using a threshold developed via the data probability density function. In addition, the inlet bathymetry is determined via depth inversion of the radar-derived frequencies and wavenumbers of the surface waves using a preexisting algorithm (cBathy). Wave height transformation is calculated through the 1D cross-shore energy flux equation incorporating the radar-estimated breaking distribution and bathymetry. The accuracy of the methodology is tested by comparison with in situ wave height observations over a 9-day period, obtaining correlation values R = 0.68 to 0.96, and root-mean-square errors from 0.05 to 0.19 m. Predicted wave forcing, computed as the along-inlet gradient of the cross-shore radiation stress was onshore during high-wave conditions, in good agreement (R = 0.95) with observations.