Atmospheric Models

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.

WRF Model

The Weather Research and Forecasting (WRF) model is a numerical weather prediction (NWP) and atmospheric simulation system designed for both research and operational applications. WRF is supported as a common tool for the university/research and operational communities to promote closer ties between them and to address the needs of both. The development of WRF has been a multi-agency effort to build a next-generation mesoscale forecast model and data assimilation system to advance the understanding and prediction of mesoscale weather and accelerate the transfer of research advances into operations. The WRF effort has been a collaborative one amongst the National Center for Atmospheric Research’s (NCAR) Mesoscale and Microscale Meteorology (MMM) Division, the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Prediction (NCEP) and Earth System Research Laboratory (ESRL), the Department of Defense’s Air Force Weather Agency (AFWA) and Naval Research Laboratory (NRL), the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma, and the Federal Aviation Administration (FAA), with the participation of university scientists. Special runs of WRF using Pseudo Global Warming (PGW) techniques will bound WRF runs with reanalysis data that has been perturbed by the estimated change from RCMS nested within GCMs under future atmospheric conditions. This provides a deterministic, dynamical downscaling of the climate model outputs to produce future weather. It is felt that future weather is a much more realistic driver for hydrological models than statistically downscaled climate models, particularly in cold regions where precipitation phase and freeze-thaw processes are important in physically based models.