The Influence Of Rossby Wave Anomalies By Stratosphere-Troposphere Interaction On The Winter Temperature Extreme Events

The vertical propagation of Rossby waves in the stratosphere-troposphere coupling system has an important influence on stratospheric and troposphric weather and climate of the Northern Hemisphere winter. The ERA-Interim daily reanalysis datasets derived from the ECMWF are employed, to analyze two adjacent stratospheric warming processes in February to March 2005 and an extreme cold event in late January 2014 occurred in the East America, to study the unique anomaly structures and evolution characteristics of Rossby waves during two events, to explore the influence that Rossby wave anomalies of smaller-scale waves represented by wave 3 on the extreme weather events of boreal winter by which propagation approach and at what time scale. The conclusions are as follows:(1) Wave 3 anomalies as the dominant factor plays an important role in two events. In 2005 stratospheric warming event, wave 3 not only directly regulates wave activity and background field of the tropopause and the lower stratosphere, reducing or enhancing the polar planetary wave guide, but also indirectly modulates wave 1 and wave 2 from monopole to dipole pattern, by interaction with the Atlantic blocking high (ridge) and altering longitudinal distribution, magnitude and direction of wave activity propagation, eventually leads to the stratospheric minor warming in the end of February 2005, warming stagnation and the stratospheric final warming of March 2005 occurred successively. For January 2014 extreme cold event in the eastern America, on the one hand, anomalously downward propagation of wave 3 modulates the longitudinal distribution of wave activity upward propagation and propagation magnitude, on the other hand, wave 3 by interaction with both the Atlantic blocking high and Alaska high, results in trough of North America deepen, the cold air breakout and maintenance. Wave 3 as a bridge to link the correlative changes of blocking high systems in two location and the energy transfer.(2) The structure and magnitude changes of Atlantic blocking high is very closely related to extreme weather events of the boreal winter, which easier interacts with smaller-scale waves represented by wave 3. The onset of the Atlantic blocking high in favor of wave activities upward propagation and stratospheric wave activities eastward propagation of its east side. Eastward propagation of stratospheric wave activities makes the high in the Pacific region develop downward and move eastward, with the result that the center of wave activities downward propagation is easier to form. Downward propagation of wave activities benefits to enhancement of the tropospheric blocking high, based on different circulation background, then giving rise to various synoptic events. It is extended time scale of collaborative change for vertical propagation of Rossby waves and blocking systems. Therefore, similar evolution of blocking high system between the Atlantic and the Pacific as well as wave activities might be seen as a precursor of extreme weather event on the extended time scale according to these two cases.