Journal
JOURNAL OF CLIMATE
Volume 26, Issue 6, Pages 2077-2095Publisher
AMER METEOROLOGICAL SOC
DOI: 10.1175/JCLI-D-12-00301.1
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Funding
- NASA [NNX06AE70G]
- NSF [ATM 0905863, AGS 0938325]
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1043307] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences
- Directorate For Geosciences [0938325] Funding Source: National Science Foundation
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A dry general circulation model is used to investigate how coupling between the stratospheric polar vortex and the extratropical tropospheric circulation depends on the latitude of the tropospheric jet. The tropospheric response to an identical stratospheric vortex configuration is shown to be strongest for a jet centered near 40 degrees and weaker for jets near either 30 degrees or 50 degrees by more than a factor of 3. Stratosphere-focused mechanisms based on stratospheric potential vorticity inversion, eddy phase speed, and planetary wave reflection, as well as arguments based on tropospheric eddy heat flux and zonal length scale, appear to be incapable of explaining the differences in the magnitude of the jet shift. In contrast, arguments based purely on tropospheric variability involving the strength of eddy-zonal mean flow feedbacks and jet persistence, and related changes in the synoptic eddy momentum flux, appear to explain this effect. The dependence of coupling between the stratospheric polar vortex and the troposphere on tropospheric jet latitude found here is consistent with 1) the observed variability in the North Atlantic and the North Pacific and 2) the trend in the Southern Hemisphere as projected by comprehensive models.
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