Stratospheric Memory and Skill of Extended-Range Weather Forecasts
Mark P. Baldwin,1
David B. Stephenson,2
David W. J. Thompson,,3
Timothy J. Dunkerton,1
Andrew J. Charlton,2
Alan O'Neill2
We use an empirical statistical model to demonstrate significant
skill in making extended-range forecasts of the monthly-mean
Arctic Oscillation (AO). Forecast skill derives from persistent
circulation anomalies in the lowermost stratosphere and is greatest
during boreal winter. A comparison to the Southern Hemisphere
provides evidence that both the time scale and predictability
of the AO depend on the presence of persistent circulation anomalies
just above the tropopause. These circulation anomalies most
likely affect the troposphere through changes to waves in the
upper troposphere, which induce surface pressure changes that
correspond to the AO.
2 Department of Meteorology, University of Reading, Reading RG6 6BB, UK.
3 Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA.
