Thursday, 26 January 2017: 10:30 AM
609 (Washington State Convention Center )
Previous research has shown that wave activity flux from the troposphere into the stratosphere can significantly impact the polar vortex and that these changes, in turn, can have an important influence on surface sensible weather. In daily data, anomalies of vertical wave activity flux from the troposphere to the stratosphere are often seen to occur as a short time-scale (two weeks or less), vertically-coherent pulse. Here, we consider the three-dimensional structure in daily data of pulses originating in the western part of northern Eurasia and their lagged relationship to the stratospheric polar vortex. A Self-Organizing Map (SOM) analysis applied to 10hPa heights is used to identify winter (Dec-Feb) days with a weak or strong stratospheric polar vortex, and an analysis of the western extent of the Siberian High is used to identify pulses. The normalized height anomalies associated with the pulse events are largest at the surface and vertically-coherent into the lower stratosphere, with some apparent eastward propagation with height. The daily frequency of a strong polar vortex changes from 31% to 9% in the 31-day average after the onset of the pulse events and the frequency of a weak polar vortex changes from 16% to 32%. For strong pulse events, the changes are from 31% to 1% and 16% to 54%, respectively, in the 31-day period after the start of the pulse event. Therefore, notable changes to the stratospheric polar vortex are directly linked to wave pulses originating at the surface in northern Eurasia.
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