Host: Aditi Sheshadri / Tim Cronin

Title: Coupling between Tropical Tropospheric and Polar Stratospheric Variability

Abstract: Tropical tropospheric variability can influence the wintertime
extratropical stratosphere. Specifically, certain phases of the
Madden-Julian Oscillation (MJO) and El Nino leads to a weakened
stratospheric polar vortex. The mechanism linking tropical
tropospheric variability to polar stratospheric appears to be common
to both El Nino and the MJO. The deepening of the wintertime Aleutian
low, as occurs e.g. during El Nino events, leads to an intensification
of the tropospheric climatological planetary wave pattern. This
increase in tropospheric planetary waves leads to increased wave
driving of the wintertime polar vortex, so that the net effect is a
weakened vortex. Once the vortex is weakened, the anomalies propagate
downwards into the troposphere and lead to the negative phase of the
Northern Annular Mode.

Faculty Host: Alan Plumb