Environmental Quality Branch

AIR QUALITY

MM5 Meteorological Data for Western Canada

Last Updated: November 1999

MM5 is a prognostic mesoscale meteorological model. In its four-dimensional data assimilation mode, MM5 uses available observational data to "nudge" its solutions towards observations, while generating dynamically consistent wind fields. Using a relatively coarse grid resolution of 20 km, MM5 can generate meteorological fields over a wide area (such as Western Canada) for a year. Unfortunately, a 20 km grid is too coarse for many air pollution applications, and annual MM5 simulations with fine scale resolution (< 1 km) are currently not practical.

This limitation can be overcome with a diagnostic model called CALMET. The diagnostic algorithms allow fine-scale terrain adjustments on the wind fields by using the coarse grid MM5-generated wind data as an "initial guess." This hybrid CALMET/MM5 approach makes it practical to produce meteorological fields on grid resolutions down to a couple of hundred metres for a full year. Thus, the MM5/CALMET partnership allows full-year, high-spatial resolution simulations to be conducted by coupling the abilities of a nonhydrostatic prognostic model with the fine-scale resolution and terrain adjustments of the diagnostic model.

CALMET is part of CALPUFF — a modeling system that is able to simulate fine-scale, three-dimensional pollutant dispersion in highly complex flow settings. The MM5 data was generated to provide wind fields for CALMET, which in turn allows the application of CALPUFF to simulate air quality in complex terrain areas. The MM5 data consists of winds and temperature for every hour of 1995 up to 18 levels above the ground, on a 20 km grid over a wide area of Western Canada.

The year 1995 was chosen because it is an emission inventory year. The data is in CALMM5 format. The following figure [under construction: link to scanned figure] shows one hour of MM5-generated winds, at one vertical level over the domain.

How to Get Access to the MM5 Data
The data and extraction software are available on CD-ROMs. Each CD-ROM covers a specified geographic area and contains hourly MM5-generated data for 1995, for that specific area. Single or multiple CDs can be ordered from the Government of British Columbia's Queen's Printer

Go to the B.C. Publications Index website and follow the links to MM5 Meteorological Data for Western Canada. Select the CD that corresponds to the geographic area you want.

For More Information:

Environmental Quality Branch
Ministry of Environment
Government of British Columbia

PO Box 9341
Stn Prov Govt
Victoria, British Columbia
Canada V8W 9M1
http://www.env.gov.bc.ca/air