Abstract
The Aleutian Low (AL) is a dominant feature of the mean circulation in the North Pacific during the winter season. The background stationary wave, air-sea interaction, and transient eddies over the North Pacific exert distinct impacts on the interannual variations of the AL intensity and position. In this study, we adopt the geopotential tendency equation to investigate the roles of various physical processes in the maintenance and interannual variation of the AL. It shows that the absolute vorticity advection plays the most important role in the formation and maintenance of the AL intensity, while the high-frequency transient eddies contribute most to both the meridional and zonal shifts of the AL. The high-frequency transient eddy vorticity forcing affects the AL through barotropic energy conversion process, and in turn the AL enhances the high-frequency transient eddies through baroclinic energy conversion process, forming a positive feedback. The associated high-frequency eddy kinetic energy anomalies exhibit an eastward movement to the east coast of North America in the years of intensified AL, which explains why the strengthening of the AL is often accompanied by an eastward movement. Furthermore, the energy conversion terms of high-frequency transient eddies are mostly located over the eastern part of the extratropical North Pacific, leading to asymmetric features in the zonal movement of the AL.