Dual-resolution ensemble analysis/forecasting system

The solution and the minimization of the cost function are defined in high, operational resolution, while the ensemble runs are performed in coarser resolution. Therefore, a control (background) forecast and the control dynamical state are defined in fine resolution, while the second moments of the PDF (e.g., covariances) are defined in coarse resolution. Since most of the computational cost of an ensemble data assimilation/forecasting system is due to ensemble forecasting, the dual-resolution approach may be a reasonable choice for future operational implementation, worth exploring.