Impact of model resolution and ensemble size on the performance of an Ensemble Prediction System

Ensemble integrations for 14 cases are described. These integrations test the relative impact of increase in ensemble size and in the resolution of the model used to integrate the ensemble. The ensembles are evaluated using a variety of statistical tests. Some of these indicate a relative advantage of an increase in ensemble size, whilst most tests suggest a relative advantage of an increase in model resolution. However, overall, the best performance was obtained by combining enhancement in model resolution (from T63L19 to T106L31) with an increase in ensemble size (from 32 to 50 members).