Séminaire
Extreme large scale North American cold events are associated with strong undulations in the tropospheric jet stream which bring cold polar air southward over the continent. We propose that these 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 PNA is associated with the first circumglobal wave pattern, North American extreme cold events are associated with the second pattern. The circulation and temperature anomalies associated with Circumglobal North American wave packet and with the strongest Eastern US cold events will be compared. We will also discuss the Asian wavepacket precursor of these events, and the possible relation to SST anomalies.
Marie-Pierre.Lefebvre@lmd.jussieu.fr