Analysis of a Conceptual Model of Seasonal Climate Variability and Implications for Seasonal Prediction

A thought experiment on atmospheric interannual variability associated with El Nino is formulated and is used to investigate the seasonal predictability as it relates to the practice of generating ensemble GCM predictions. The purpose of the study is to gain insight on two important issues within seasonal climate forecasting: (i) the dependence of seasonal forecast skill on a GCM's ensemble size, and the benefits to be expected from using increasingly larger ensembles, and (ii) the merits of dynamical GCM techniques relative to empirical statistical ones for making seasonal forecasts, and the scenarios under which the former may be the superior tool.