Interannual Variability of the January Tropospheric Meridional Eddy Sensible Heat Transport in the Northern Latitudes

Abstract

Evidence of large temporal and spatial variability in the eddy fluxes of sensible heat in the lower troposphere (100-50 kPa layer) in January, from 1946 to 1987, is presented.
The January climatological (1946-87) spatial distribution of the meridional standing eddy heat flux is characterized by four main features, or "centers of action": (1) a region north of Korea (extreme eastern Siberia), (2) northeastern Atlantic Ocean, (3) the Gulf of Alaska, and (4) a region over midwestern Canada. Even though the center just north of Korea is the most intense, much of the interannual variability of the meridional January standing eddy sensible heat transport is associated with the two centers over the northeastern Atlantic and the Gulf of Alaska. Spatial and temporal variability of these centers are correlated with the intensities of the Icelandic Low and the Aleutian Low, respectively. The standing eddy heat transport in the Greenland Sea is well correlated with the ice margin there during years of large abnormal heat transport by the standing eddy component. The long term variability of the heat transport over the period 1946-87 shows a clear interdecadal signal in the Gulf of Alaska. Over the North Atlantic, the variability is instead dominated by a large perturbation in the early 1970's.
The January climatological spatial distribution of the meridional transient eddy heat flux is dominated by a center over the Aleutian Peninsula, and an elongated cell stretching from eastern United States to North Sea, with a center off Newfoundland and another over Iceland. The spatial pattern follows closely the climatological tracks of baroclinic disturbances, i. e., synoptic storms. The geographical distribution of the spatial and temporal variability of the January meridional transient eddy heat flux is less organized than the pattern associated with the standing eddy heat flux. Much of the variability is confined to the western hemisphere, from the mid-North Atlantic Ocean, across North America, to the eastern half of the North Pacific. The centers of variability are located at (1) Gulf of Alaska, (2) western and eastern Canada, and (3) southeastern United States.