Abstract

At Canadian meteorological center (CMC), we are currently implementing the future 15-km operational deterministic global forecast system. In the horizontal we use spherical coordinates on the overset Yin-Yang grid while in the vertical, we use a log-hydrostatic-pressure coordinate on the Charney-Phillips grid. The global forecast on the Yin-Yang grid is performed by considering a domain decomposition (a two-way coupling method) between two limited-area models (LAM), discretized on the two panels of Yin-Yang grid and using the same time step. Each panel of the Yin-Yang grid system is extended by a static halo region that plays the same role as the piloting region in limited-area modeling. Since the two sub-grids of the Yin-Yang grid do not match, the update of the variables in the pilot region is done by interpolation.

Each limited-area model uses the same fully implicit semi-Lagrangian method as in the GEM operational model to solve its own dynamic core. Geophysical fields are produced separately for each LAM grid however, The two LAM models use the same parametrization schemes for the physics configuration. For data assimilation, we use the Ensemble-Var (En-Var) approach where the 4D ensemble covariances are used to produce 4D analysis without TL/AD models.

In this presentation we will present some preliminary results of this work.