The relationship between the Polar-night Jet Oscillation (PJO) and the Annular Mode (AM) is examined based on a correlation analysis of winter in both the Northern Hemisphere (NH) and Southern Hemisphere (SH). The PJO becomes a nearly zonally symmetric structure from the troposphere to the upper stratosphere when a pattern similar to the AM appears at the troposphere. If the signal of the PJO is removed, the signal of the AM exists only in the troposphere, and the persistency of the signal is largely reduced in the stratosphere. This suggests that the AM is essentially a tropospheric process that tends to strongly interact with the PJO in the active season.