An Extratropical Contribution to the Signal‐To‐Noise Paradox in Seasonal Climate Prediction

Abstract

AbstractSkillful seasonal prediction of northern hemisphere mid‐latitude winter climate has become a reality in the last decade, but its practical applications are hampered by the “signal‐to‐noise paradox,” in which predicted signal amplitudes are much smaller than expected from the correlation with observations. Various hypotheses for the paradox have been advanced. Here we test whether we can identify a contribution from extratropical processes. To do this, we use ensembles of numerical experiments in which the tropical dynamical state is relaxed toward observationally based reanalysis. This allows us to remove errors in the representation of the tropical sources of teleconnections to mid‐ and high‐latitudes. We find that a signal‐to‐noise paradox remains present in our relaxation experiments, implying that at least part of the origin of the paradox must arise from errors in simulating processes in the extratropics. This finding helps to narrow the search for its ultimate cause.