Large-eddy simulation of a cold-air outbreak over the Gulf stream

Cold air outbreaks during the winter along the east coast of North America often lead to large ocean heat fluxes as Arctic air moves over the relatively tropical waters of the Gulf stream. Temperature differences between the ocean and atmospheric marine boundary layer (MBL) are frequently order 20 ^oC, driving sensible and latent heat fluxes over 1000 W m^-2. Because the local heat flux depends on upstream changes in the MBL, simulations of fluxes by numerical models are dependent on boundary layer properties such as MBL depth and boundary layer entrainment. In this study, we examine how the MBL changes when cold air passes over a large sea-surface temperature front. A combination of rawinsonde data taken during the CLIMODE experiment and large-eddy simulation results are used to quantify the effects of MBL changes on surface fluxes.