Temporal and spatial structure of wind stress curl over the North Atlantic

"Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An EOF analysis is performed on this field resulting in variance-qualified spatial patterns of wind stress curl and associated time series. A Monte Carlo technique is used to establish the statistical significance of each spatial pattern. The first four statistically significant EOF modes represent more than 50% of the curl variance. The spatial patterns of curl associated with these modes exhibit many elements of North Atlantic climatology. The associated time series are spectrally analyzed. Most of the variance is contained in annual and semiannual frequencies. Features observed include the individual annual variation of the subtropical high and the subpolar low, the annual oscillation of intensity between the above pressure centers, the influence of localized strong SST gradients and associated cyclogenesis regions, and the constant nature of the trades. The EOF curl patterns are in the form of simple standing waves with wavelength on the order of basin size"--Abstract.