סמינר בחוג לגיאופיזיקה: The Circumglobal North American wave pattern and its relation to North American cold events

Abstract:

The polar vortex has "made headlines" in recent years following anomalously cold Eastern US winters alongside continuing drought conditions in California, particularly striking during winter 2013-14. These conditions were associated with strong undulations in the tropospheric jet stream which bring cold polar air southward over the Eastern part of the continent, and warm dry conditions over the south west.  Recent studies have associated these undulations with anomalous Pacific SST anomalies. In particular, an unusual blob of warm sea surface temperatures developed in the Gulf of Alaska during winter 2013-14. We propose that the jet undulations are associated with the North American part of the Circumglobal Teleconnection Pattern - a pair of zonally oriented waves of zonal wavenumber 5 which are in zonal quadrature with each other. While the known Pacific North American teleconnection pattern is associated with the first circumglobal wave pattern, Eastern North American extreme cold events are associated with the second pattern. The implications of this association regarding the physical drivers of such cold events will be discussed, in particular Asian wavepacket precursors, and the possible relation to SST anomalies. 

מארגן הסמינר: פרופ' איל חפץ