GFI/BCCR Seminar: Maintenance of Baroclinicity in the Atlantic Storm Track (and its Relation to the Sea Surface Temperature Gradient along the Gulf Stream)
Hovedinnhold
Thomas Spengler (GFI): Maintenance of Baroclinicity in the Atlantic Storm Track (and its Relation to the Sea Surface Temperature Gradient along the Gulf Stream) Abstract We find that adiabatic tilting flattens the isentropic surfaces, reflecting the action of growing baroclinic cyclones. This tendency is balanced climatologically by the generation of isentropic slope by diabatic processes. In the lower troposphere, the most intense diabatic increase of slope is found along the oceanic frontal zone associated with the Gulf Stream and at higher latitudes in the Labrador Sea, the Nordic Seas and the Barents Sea. Latent heat release and sensible heat fluxes both contribute substantially in these regions. A quantitative analysis of cold-air outbreaks emphasizes their important role in restoring the slope in the lower troposphere over the Gulf Stream region and off the sea-ice edge at high latitudes. We also present composites of strong events of slope tendency and latent heating as well as surface fluxes, pinpointing the relative contribution of the cold or warm sector of a cyclone to the slope tendency in the Gulf Stream region. In the upper troposphere, latent heat release due to cloud microphysical processes is the dominant mechanism maintaining the slope. |