On the dynamical coupling of long-term changes in stratospheric wave one structure and tropospheric Rossby wave developments

The decadal variability of observed stratospheric wave one structure, as seen in temperature, geopotential or potential vorticity, can assumed to be forced mainly by tropospheric wave activity propagating upward. On the other hand, decadal changes in stratospheric wave one structure may have an influence on tropospheric wave activity via configuring the large-scale flow in the upper troposphere / lower stratosphere region. The aim of this study is to elucidate the coupling between the long-term behaviour of stratospheric wave one structure and stationary Rossby wave developments in the troposphere, based on ECMWF Reanalysis data (ERA-40) and model sensitivity experiments with a simplified version of the GCM ECHAM. In particular, we have analyzed observed and modelled PV-fields and stationary wave activity fluxes, which illustrate that long-term means of Rossby wave breaking behaviour, which maximize over the Northern Pacific / North America region and over the Northern Atlantic / European region, may be influenced strongly by the amplitude and the phase of the stratospheric wave one structure. Also, the results suggest an efficient dynamical feedback-loop between long-term changes in stratospheric wave one structure and tropospheric Rossby wave breaking behaviour. Possible relations to observed long-term variability modes like NAO are discussed.