Impacts of differential surface friction upon the relative intensity of the Atlantic and Pacific storm tracks

The Atlantic jet is much weaker than the Pacific jet in winter and yet the Atlantic storm track is substantially more intense than the Pacific storm track. This seemingly counter-intuitive statistical property of the general circulation has not been accounted for. This study examines the dynamical consequence of one specific process that could significantly contribute to this feature of the general circulation.

It is hypothesized that the differential impacts of land versus ocean surfaces around the hemisphere in mid-latitude on synoptic disturbances could be a significant factor controlling the relative intensity of the Atlantic and Pacific storm tracks. In particular, we focus on the impact of differential surface friction in this study. This hypothesis is tested in the context of a barotropic model in which there is an external forcing to support two localized jets with characteristics crudely comparable to those of the Atlantic and Pacific jets. The drag coefficient over the land sectors is several times larger than that over the oceanic sectors. By comparing the statistical characteristics of the circulation in two sets of experiments with and without surface differential damping, the analysis confirms that the model Atlantic storm track is indeed more intense than the model Pacific storm track. This overall model result may be taken as a supporting evidence for the hypothesis. The nature of the processes giving rise to such statistical characteristic of a turbulent flow is diagnosed. The counterpart results of a more general model setting will be discussed.