An investigation of diurnal variability in wind and ocean currents off Huntington Beach, California

Abstract

In conjunction with the Huntington Beach Phase III Investigation, the diurnal variability in the wind and ocean currents from July 1 - October 12, 2001 over the San Pedro Shelf is investigated. Results suggest that the diurnal currents are driven by the diurnal winds but that the strength of the ocean response is modulated by the low frequency flow regime. The spectral peak of the near-surface currents is at the diurnal frequency, which is below the inertial frequency (1.107 cpd). The diurnal currents are surface-intensified, decaying with depth to a minimum at 10-13 m and increasing slightly in strength below that. The near-surface diurnal currents are in phase across the shelf, and are close to in phase with the winds over the shelf. The amplitude modulation of the diurnal energy of the ocean currents is correlated with the direction of the low frequency flow along the shelf;the energy is enhanced when the flow is equatorward, and weak when the flow is poleward. The amplitudes of the diurnal near-surface currents are also correlated with the diurnal winds. However, the low frequency currents and winds are not well correlated.