Global Environmental Muti-Scale Model (GEM) Model
GEM is the operational Global Environmental Muti-Scale Model used in Numerical Weather Prediction operationally in Canada by ECCC. It has limited ability to be run outside of the operational community in ECCC. It is essentially an integrated weather forecasting and data assimilation system developed in the Recherche en Prévision Numérique (RPN), Meteorological Research Branch (MRB), and the Canadian Meteorological Centre (CMC). The GEM Global Forecast System (GFS runs out to 16 days) and 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.
The Regional Deterministic Prediction System or RDPS for the coarser mesh and High Resolution Deterministic Prediction System or HRDPS for the finer mesh are produced by ECCC 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.
Given the multi-scale capability of the GEM model and the need for higher resolution forecasts over Canada, the CMC runs an experimental version of the model which has a resolution higher than the operational regional version of the same model. Two runs of this model are initiated every day, one having its region of interest centered over the western part of the country and the other over the eastern part. This version of the model is to be used as a test bed for new parameterizations, improved high resolution surface parameters, etc. in the context of a better resolved topography and land-sea mask.
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.