Intra-seasonal stratosphere-troposphere coupled variability
Contacts: Amy Butler (amy.butler@noaa.gov); Andrew Charlton-Perez (a.j.charlton@reading.ac.uk); Edwin Gerber (gerber@cims.nyu.edu); Tiffany Shaw (tas2163@columbia.edu)
Sudden Stratospheric Warming Events:
Sudden straospheric warmings (SSWs) and other interseasonal variability play a key role in the link between the stratosphere and the troposphere. This DynVar Research Group seeks to examine the simulation of SSWs, their properties and their changes over this century by climate models such as those used in CMIP5 and SHFP.
Definition of SSWs:
Discuss how SSWs are formally defined and how we might update the definition, see the SSW forum.
Extratropical Wave Coupling:
Planetary waves represent the most important source of dynamical coupling between the stratosphere and troposphere. Our aims are to examine the simulation of planetary scale waves including their upward and downward propagation and related impacts on the zonal-mean flow; and to understand how changes in greenhouse gases and stratospheric ozone impact planetary wave propagation and consequently stratosphere-troposphere coupling.
Annular Modes and Stratospheric Memory:
The annular mode patterns of variability can be used to characterize the coupling between the stratospheric polar night jets and the tropospheric mid-latitude jets and storm tracks. Variations in the planetary wave activity emanating from the troposphere drive variability in the strength of the stratospheric vortex, while stratospheric conditions in turn appear to influence the position of the tropospheric storm tracks. Within this DynVar Research Group, we are particularly interested in potential for the long time scales in the lower stratosphere, "stratospheric memory", to affect the persistence of tropospheric weather regimes. Can this coupling affect seasonal forecasts, and how important is it to the overall climate of the troposphere and stratosphere? We would also like to better understand the mechanism(s) behind the coupling.