Joint Seminar: Cold spell coming up? Dynamics of sudden stratospheric warmings and their impact on week 2-6 forecasts

It is by now well established that certain stratospheric flow configurations may alter tropospheric dynamical variability. Such flow configurations include the aftermath of sudden stratospheric warming events (SSWs), such as an increased likelihood for cold spells over Eurasia (as statistically expected associated with the currently evolving SSW). Although the detailed mechanisms behind this stratosphere-troposphere coupling remain elusive, most aspects of it are by now empirically well-known. For example, the coupling involves feedbacks between upward propagating planetary waves of tropospheric origin and the mean flow, the tropospheric response involves synoptic-scale eddy feedbacks, SSWs tend to project onto negative anomalies of the Arctic and North-Atlantic Oscillation (AO, NAO). Here I will highlight some recent results on 1) the importance of the tropopause layer in the dynamical coupling between the troposphere and stratosphere, 2) the stratospheric influence on the evolution of baroclinically unstable waves during their non-linear decay phase, 3) the improved quantification of the stratospheric modulation of AO extremes based on extended-range ensemble forecasts.

Date

02.03.2023

Time

15:15 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Thomas Birner, LMU M√ľnchen

Organizers

Hauke Schmidt

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