Project Details
Projekt
A multiscale perspective on the role of sudden stratospheric warmings in North-Atlantic flow transitions
Subject Area
Atmospheric Science
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 553750934
It is well established that strong anomalies of the wintertime stratospheric flow, such as sudden stratospheric warmings (SSWs), are followed by large-scale tropospheric circulation anomalies over the course of several weeks. These tropospheric anomalies tend to manifest most strongly over the North Atlantic and give rise to sub-seasonal predictability. At the same time, the underlying mechanisms for the tropospheric response to SSWs, including its regional nature, remain incompletely understood. Here, we propose to tackle the stratosphere-troposphere coupling problem from a new multi-scale perspective. We hypothesize that the anomalous stratospheric zonal mean flow following SSWs first alters the planetary wave activity throughout the stratosphere-troposphere system, and that subsequently the altered planetary wave structure in the troposphere modifies the waveguide for synoptic eddies. The modified waveguide, in combination with the omnipresent eddies, favors a flow transition over the Atlantic-European sector, and this ultimately changes the likelihood for the occurrence of specific flow patterns in this region. In our analysis we will use a linear model to test the hypothesis that the anomalous stratospheric conditions modify planetary wave propagation throughout the stratosphere-troposphere system. We will further develop and apply a method to compute a tropospheric background state that includes planetary-scale variations and, at the same time, is relevant for the evolution of synoptic-scale eddies. The latter diagnostic will allow us to examine modifications of the background state due to the modified planetary wave pattern. Our analysis will be based on both reanalysis data and a specifically designed set of ensemble simulations with a state-of-the-art numerical weather prediction model.
DFG Programme
Research Grants
Co-Investigators
Professorin Dr. Hella Garny; Privatdozent Dr. Michael Riemer
