Manifestations of Different El Nino Types in the Dynamics of the Extratropical Stratosphere

The behavior of planetary waves and their influence on the global circulation of the Northern Hemisphere during different El Nino types is studied. Three sets of five boreal winters were chosen for each El Nino type: Modoki I and II and canonical El Nino. Based on data of the Japanese 55-year Reanalysis and the Modern-Era Retrospective Analysis for Research and Applications, the spatio-temporal structure of planetary waves and the residual mean circulation were analyzed. The results show that the canonical El Nino type is characterized by the weakest wave activity in March. It is also demonstrated that warming of the polar stratosphere, accompanied by maximizing wave activity and weakening of the zonal wind, may lead to earlier stratospheric polar vortex collapse and the early spring transition under Modoki I conditions. This study is the next step in understanding of the so-called long-range teleconnections, consisting of the propagation of a signal from the tropical El Nino Southern Oscillation source into the polar stratosphere.