Influence of eddy-driven jet latitude on North Atlantic jet persistence and blocking frequency in CMIP3 integrations

Abstract

The distribution of daily North Atlantic jet latitude is analyzed in 45 CMIP3 integrations. It is demonstrated that models that place the jet equatorward of its observed position have more positively skewed jet latitude distributions, while models that correctly place the jet have symmetric distributions like that of the observations. The jet is shown to be more persistent at equatorward latitudes compared to poleward latitudes, consistent with previous findings in the Southern Hemisphere. There is a robust decrease in annual blocking frequency as the jet shifts poleward with global warming, with larger decreases seen for models with larger jet shifts, consistent with the effect of latitude on jet persistence. These results imply that model biases of jet latitude of 1°-2° could result in large differences in jet variability and frequency of extreme events predicted for the future. © 2010 by the American Geophysical Union.