Storm tracks and zonal mean flow variability: a comparison between observed and simulated data

A statistical technique is used to analyze the relation between monthly mea n zonal flow and storm tracks activity in the observations and numerical si mulations (ECHAM4 model). The singular value decomposition technique (SVD) has been used to correlate storm tracks and monthly mean wintertime anomaly fields. The analysis has been performed on data from January 1980 to Decem ber 1989 (NMC analyses) and on an ensemble of AGCM simulations with prescri bed SST for the same period, separately in the Euro-Atlantic and Pacific se ctors. We found good correlation between storm tracks activity and zonal fl ow in both regions. In both data and simulations the dominant SVD modes sho w that the storm tracks spatial displacement is in conjunction with jet shi fts in the same direction. Our analysis suggests that the model is highly s ensitive to the equatorial ocean forcing. Although the model produces an ex cessive response to El Nino and La Nina phases, it shows good capability of simulating the dynamical connection between storm tracks and jet.