Journal Highlights

Evaluating the tradeoffs between ensemble size and ensemble resolution in an ensemble-variational data assimilation system

Editors’ Highlight—

This paper examines a fundamental question in the modern era of ensemble weather forecasting: what is a better use of additional computer resources, increasing the spatial resolution of the forecast model or increasing the ensemble size? Although both changes improve forecast performance in the National Centers for Environmental Prediction operational forecast and data assimilation system, increasing model resolution leads to slightly but significantly more improvement. Much of the benefit of increasing resolution comes from reducing small-scale errors, and eliminating the need for a single deterministic very-high-resolution control forecast, replacing it with an ensemble average.