ENSO's effect on Alaska during opposite phases of the Arctic Oscillation

Abstract

The NCEP Reanalysis and station data are used to investigate how the winter weather of Alaska during El Niño/Southern Oscillation (ENSO) events has varied during different phases of the Arctic Oscillation (AO). Much greater 500-hPa geopotential height, 1000-hPa air temperature, and precipitation anomalies in association with ENSO tend to occur in the negative phase of the AO; these anomalies cannot be attributed to the AO on its own. Analysis of case-to-case variability indicates that the ENSO/AO composite results are robust. It is also shown that much of the variability of the ‘Pacific pole’ of the AO is associated with those winters with El Niño/AO- and La Niña/AO+ conditions, suggesting that this pole is much less robust than its counterpart in the North Atlantic. To the extent that winter mean state of the AO can be predicted, our results indicate that incorporation of the state of the AO would provide useful information for improving seasonal weather forecasts in the vicinity of Alaska. Copyright © 2006 Royal Meteorological Society