Scales of North Atlantic wind stress curl determined from the comprehensive ocean‐atmosphere data set

Abstract

Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An empirical orthogonal function (EOF) analysis is performed on this field, resulting in 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 the major 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 sea surface temperature gradients and associated cyclogenesis regions, and the constant nature of the trades. The EOF curl patterns are in the form of basin‐sized standing waves.