Local and shoaled comparisons of sea surface elevations, pressures, and velocities

Abstract

Sea surface elevations, or pressures, and velocities were measured at closely spaced (wavelength or less) locations in a line extending from 10‐m depth to inside the surf zone at Torrey Pines Beach, San Diego, California. Intercomparisons of local pressure, velocity, and sea surface elevation spectra for the wind wave frequencies (0.05–0.3 Hz) were made by using linear wave theory. Errors in both total variance and energy density in a particular frequency band are less than 20% both inside and outside the surf zone, except in the immediate vicinity of the breakpoint, where larger disparities are observed. Surface elevation spectra calculated at 10 m were shoaled by using linear wave theory. The total variance of stations between 10‐ and 3‐m depth are typically predicted with less than 20% error, although harmonic amplification and other nonlinear effects can lead to significant errors in the prediction at particular frequency bands. Observations inside 3‐m depth significantly departed from the predictions of linear shoaling theory.