The general circulation responses of high-resolution North Atlantic Ocean models to synthetic scatterometer winds

Abstract

High-resolution (1/5° × 1/6°) quasigeostrophic models of the North Atlantic Ocean are forced by daily wind stress curl fields of controlled wavenumber content. In the low-wavenumber case, the wind stress curl is derived from a low-pass filtering of ECMWF wind fields such that the retained wavenumber band is observed to obey a k-2 power law in the spectrum for each day (where k is the wavenumber vector). In a second case, the wavenumber content of the wind stress curl fields is comparable to that derivable from an ideal scatterometer-wind dataset. Decadal-average streamfunction fields are compared with a climatology of dynamic topography and compared between the model calculations driven by these synthetic wind stress curl datasets with the goal of testing the sensitivity of the general circulation to high-wavenumber forcing. The largest signal in decadal-average streamfunction response to high-wavenumber forcing occurs in the eastern basin of the North Atlantic. Fields of mean kinetic and eddy kinetic energies are enhanced in the eastern basin of the North Atlantic by 0.5 and 1.0 orders of magnitude, respectively, in calculations forced by the scatterometer-like wind stress curl. Model solutions are compared with the implied Sverdrup streamfunctions for each forcing dataset, and parallel experiments are performed with a linearized quasigeostrophic model. Conclusions are drawn regarding the operative dynamics and the wavenumber band of importance in improving the model general circulation. It is noted that present day and planned scatterometer missions are capable of resolving the requisite spatial scales.