Atmosphere–Ocean Coupled Dynamics of Cyclones in the Midlatitudes

Abstract

It is well known that hurricane intensity is influenced by factors such as the storm's initial intensity, the spatial extent of the storm, the thermodynamic state of the atmosphere through which it moves, the storm propagation speed, and sea surface fluxes along the storm track. Although several of these factors are also known to modulate the strength of midlatitude cyclone systems, little is known about the impact of air?sea interactions on storms outside the Tropics. To investigate the atmosphere?ocean dynamics of midlatitude North Atlantic storms, the Canadian Mesoscale Compressible Community (MC2) atmospheric model is coupled to the Princeton Ocean Model. Case studies include midlatitude extratropical storm Earl (1998) and an intense winter storm from January 2000, hereafter denoted Superbomb. On one hand, late-summer storms such as Earl encounter a thin mixed layer and produce a cold wake by inducing strong currents. Sea surface temperatures (SSTs) can be depressed as much as 5°C or more. On the other hand, winter storms such as Superbomb occur when the mixed layer is quite deep. Although impacts on SSTs and the upper-ocean temperature profile tend to be weak, about 1°C or so, storm-induced ocean currents can be large. In the specific cases of Earl and Superbomb, little impact on cyclone strength was detected.