Global Environmental Multiscale Model

The Global Environmental Multiscale Model (GEM), is an integrated forecasting and data assimilation system developed in the Recherche en Prévision Numérique (RPN), Meteorological Research Branch (MRB), and the Canadian Meteorological Centre (CMC). Along with the NWS's Global Forecast System (GFS), which runs out to 16 days, the ECMWF's Integrated Forecast System (IFS), which runs out 10 days, the Naval Research Laboratory Navy Global Environmental Model (NAVGEM), which runs out eight days, and the UK Met Office's Unified Model, which runs out to 6 days, it is one of the five predominant synoptic scale medium-range models in general use.

The GEM's operational model, known as the Global Deterministic Prediction System (GDPS), is currently operational for the global data assimilation cycle and medium-range forecasting, the regional data assimilation spin-up cycle and short-range forecasting. Furthermore, mesoscale forecasts (distributed under the names Regional Deterministic Prediction System or RDPS for the coarser mesh and High Resolution Deterministic Prediction System or HRDPS for the finer mesh) are produced overnight and are available to the operational forecasters. A growing number of meteorological applications are now either based on or use the GEM model. Output from the GEM goes out to 10 days, on par with the public output of the European Integrated Forecast System.

The ensemble variant of the GEM is known as the Global Ensemble Prediction System (GEPS). It has 20 members (plus control) and runs out 16 days, the same range as the American Global Forecast System. The GEPS runs alongside the GFS ensemble to form the North American Ensemble Forecast System. A Regional Ensemble Prediction System (REPS), covering North America and also having 20 members plus control, runs out 72 hours.

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