Periodic Variation of the Winter Stratospheric Circulation and Intermittent Vertical Propagation

[摘要] Analyses of day to day variations of planetary waves and those of the mean zonal wind in the stratosphere are made throughout the period of five winters from 1963 to 1967 based on the gridpoint data of 30mb geopotential height together with the stratospheric synoptic charts. The monthly mean structure of planetary waves suggests the upward propagation of wave energy from the troposphere into the stratosphere. Day to day variations of the polar-night westerlies and those of the amplitude of wave number one at the 30-mb level show a periodicity of about two weeks, and a significant negative correlation is found between these two quantities. It is found that the wave amplification propagates upward when the mean zonal wind is relatively weak westerly. This suggests that the periodic variation of planetary waves is caused by the “time-dependent” energy propagation from the troposphere in response to the time change of the mean zonal wind in the stratosphere.Although the divergence of horizontal momentum transport due to the planetary waves is not always in good agreement with the time change of the polar-night westerlies, we may expect a possibility of the existence of an “index cycle” caused by the wave-zonal flow coupling for the stratospheric circulation.

[学科分类] 大气科学