A Multidimensional Spectral Description of Ocean Variability

Abstract

n updated empirical, analytical model for the frequency and wavenumber distribution of balanced motion in the ocean is presented. The spectrum model spans periods longer than the inertial but shorter than a decade and wavelengths between 100 and 10 000 km. Assuming geostrophic dynamics, a spectrum model for the streamfunction is constructed to be consistent with a range of observations, including sea surface height from satellite altimetry, velocity from moored and shipboard instruments, and temperature from moorings. First-order characteristics of the observed spectra, including amplitude and spectral moments, vary slowly geographically. The spectrum model is horizontally anisotropic, accommodating observations that zonal wavenumber?frequency spectra are dominated by a ?nondispersive line.? Qualitative and quantitative agreement is found with one-dimensional frequency and wavenumber spectra and observed vertical profiles of variance. Illustrative application is made of the model spectrum to observing-system design, data mapping, and uncertainty estimation for trends.