Study on mechanism of formation and variability of the Arctic Oscillation

点击翻译按钮获取中文摘要

The Arctic Oscillation the most dominant variation mode of the wintertime sea-level pressure in the Northern extratropics and it is the seesaw variation between the midlatitudes and the Arctic region. It has an equivalent barotropic structure and it has a signal up to the lower stratosphere. This mode resembles the North Atlantic Oscillation, but it is more annular and global. It was named as the Arctic Oscillation by Thompson and Wallace(1998).A perpetual February simulation by an AGCM clearly showed the Arctic Oscillation is not a forced mode but an internal mode of the atmosphere. The composite analysis of the simulation results showed the dominance of the Arctic Oscillation is caused by the wave-mean flow interaction. Mostly planetary-scale wave contributes to the transition to positive and negative phases of the Arctic Oscillation and the synoptic-scale wave also contributes to the transition.The perpetual February experiment also shows that the wintertime Arctic Oscillation is related to the polar night jet oscillation in the stratosphere. When the polar night jet is stronger than normal, the Arctic Oscillation in the troposphere tends to shift to posituve phase.In reality after the stratospheric sudden warming, which corresponds to weak polar night jet and negative phase of the stratospheric Arctic Oscillation, the tropospheric Arctic Oscillation tends to have a negative phase, which bring severe cold weather in midlatitudes.In interannaul and intraseasonal time scales, the Arctic Oscillation has a good correlation with the winter climate over Eurasia, northern Japan and Sea of Okhotsk. Analyzing the sea ice extent over Sea of Okhotsk, it is found that the sea ice extent has a good correlation with the Arctic Oscillation(also with the North Atlantic Oscillation).