Understanding the zonal response to teleconnections

Despite receiving a large amount of attention over the past 30 years, certain aspects of the dynamics of atmospheric teleconnections remain poorly understood. For example, on seasonal timescales, why does warming in the tropical Pacific Ocean lead to equatorward excursions of the northern polar night jet, whereas warming in the tropical Indian Ocean seems to cause the jet to move poleward? And by what mechanism could regional snow cover anomalies affect the jet position? In this talk, I will present recent work using numerical experiments with a hierarchy of atmospheric GCMs to address these questions. Our findings suggest a rather simple and intuitive dynamical framework for understanding these zonal mean responses. It is shown that the sign and strength of the zonal response is often related to the phasing, and hence the linear interference, between the Rossby wave response and the climatological stationary waves. I will discuss the applicability of these findings to "bigger picture" problems, such as understanding the origin of trends in surface temperature over North America since the 1950s.