Dependence of the climatological axial latitudes of the tropospheric westerlies and storm tracks on the latitude of an extratropical oceanic front



[1] Major “storm tracks”, where migratory cyclones and anticyclones recurrently develop, are observed around midlatitude oceanic frontal zones with strong meridional gradient of sea-surface temperature (SST). A set of atmospheric general circulation model experiments is performed with zonally uniform SST prescribed at the model lower boundary. The latitudinal SST profile for each hemisphere is characterized by a single front. The frontal latitude is varied systematically from one experiment to another, while the intensity of the frontal gradient is kept unchanged. Though idealized, the experiments reveal a climatological tendency for a low-level storm track to be organized along or slightly poleward of the SST front if located in the subtropics or midlatitudes. As a surface manifestation of an eddy-driven polar-front jet (PFJ), surface westerly axis tends to form on the poleward flank of the front. This anchoring effect of the SST front is also hinted at upper levels, but the climatological positions of the storm track and PFJ are less sensitive to the frontal latitude. For the SST front at subpolar latitude, the joint primary axes of the upper-level storm track and PFJ form in midlatitudes away from the SST front. Their positions correspond to their counterpart simulated with a particular SST profile from which frontal gradient has been removed, suggesting that the anchoring effect of a subpolar SST front on the storm track and PFJ is overshadowed by atmospheric internal dynamics, namely, the self-maintenance mechanism of a midlatitude storm track and PFJ through their interactions.