Transient eddy forcing of the rotational flow during northern winter

Abstract

The total direct transient eddy forcing of the vorticity balance in the upper troposphere during northern winter is examined using 11 years of 2 to 8-day bandpassed global analyses. Most examinations of the importance of high-frequency eddy vorticity fluxes to the maintenance of either the climatological standing waves or low-frequency anomalous flows have focused on only the horizontal flow or the rotational component of the horizontal transient flow. The respective roles of each transient eddy term in the vorticity equation in maintaining two large-scale, low-frequency anomalous flows are also examined. One case involves a pronounced circulation anomaly that persisted for more than a decade over the North Pacific, and the second case relates to the maintenance of extremes of the North Atlantic Oscillation. -from Author