15km Resolution Numerical Data of the Regional Deterministic Prediction System (RDPS) - GRIB2 format

Under the Regional Determinisitic Prediction System (RDPS), the GEM model is run on a variable-step grid with a finer central core resolution. Most fields in the 15km resolution GRIB2 dataset are made available on a 493x399 polar-stereographic grid covering North America and adjacent waters with a 15 km resolution at 60°N. Five fields only, in the GRIB2 dataset, are made available on a 245x190 polar-stereographic grid with a 35 km resolution at 60°N

Technical Grid Specification

15km resolution geographical grid coverage

Grid specifications for all but 5 fields

Table lists the values of various parameters of the 15km resolution polar-stereographic grid except for five fields .

Parameter Value
ni 493
nj 399
resolution at 60° N 15 km
coordinate of first grid point 32.549° N
134.62° W
(i,j) coordinate of North Pole (175.0, 399.0)
grid orientation
(with respect to j axis)
-111.0°

There is also a formatted ASCII file containing geographical coordinates for each grid point in compresssed format.

Technical Grid Specification for HLCY 4LFTX SHOWA CAPE WCHIL

35km resolution geographical grid coverage

Grid specifications for
HLCY 4LFTX SHOWA CAPE WCHIL
only

Table lists the values of
HLCY 4LFTX SHOWA CAPE WCHIL
produced on a 35km resolution polar-stereographic grid.

Parameter Value
ni 245
nj 190
resolution at 60° N 15 km
coordinate of first grid point 20.5833° N
135.3754° W
(i,j) coordinate of North Pole (103.1, 195.3)
grid orientation
(with respect to j axis)
-111.0°

There is also a formatted ASCII file containing geographical coordinates for each grid point in compressed format.

Download

The data is available using the HTTP protocol and resides in a directory that is plainly accessible to a web browser. Visiting that directory with an interactive browser will yield a raw listing of links, each link being a downloadable GRIB2 file. In practice, we recommend writing your own script to automate the downloading of the desired data (using wget or equivalent). If you are unsure of how to proceed, you might like to take a look at our brief wget usage guide.

The data can be accessed at the following URLs:
http://dd.weatheroffice.gc.ca/model_gem_regional/15km/grib2/HH/hhh/

where:

  • HH: model run start, in UTC [00,12]
  • hhh: forecast hour [000,003,006,...,048]

File name nomenclature

The files have the following nomenclature:
CMC_reg_Variable_LevelType_level_ps15km_YYYYMMDDHH_Phhh.grib2

where:

  • CMC: constant string indicating that the data is from the Canadian Meteorological Centre
  • reg: constant string indicating that the data is from the GEM RDPS Model
  • Variable: Variable type included in this file. To consult a complete list, refer to the variables section.
  • LevelType: Level type. To consult a complete list, refer to the variables section.
  • Level: Level value. To consult a complete list, refer to the variables section.
  • ps15km: constant string indicating that the projection used is polar-stereographic at 15km resolution.
  • YYYYMMDD: Year, month and day of the beginning of the forecast.
  • HH: UTC run time [00,12]
  • Phhh: P is a constant character. hhh is the forecast hour [000,003,006,...,048]
  • grib2: constant string indicating the GRIB2 format is used

Example of file name:
CMC_reg_DEPR_ISBL_1015_ps15km_2010091306_P027.grib2

This file originates from the Canadian Meteorological Center (CMC) and contains the data of the GEM RDPS. The data in the file start on September 13th 2010 at 06Z (2010091306). It contains the dew point depression (DEPR) at the isobaric level 1015 mb (ISBL_1015) on a polar-stereographic at 15km resolution (ps15km) for the forecast hour 27 (P027) in GRIB2 format (.grib2).

Levels

Vertical coverage of three-dimensional fields is provided by up to 28 isobaric levels.

Isobaric levels (hPa): 1015, 1000, 985, 970, 950, 925, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 275, 250, 225, 200, 175, 150, 100, 50.

Some fields receive limited three-dimensional coverage of 4 levels in the vertical.

Isobaric levels (reduced coverage, hPa): 850, 700, 500, 250.

Additional levels that may be applicable to a given parameter are:

  • surface
  • fixed height above ground
  • fixed height below ground
  • thickness between two isobaric levels
  • nominal top of the atmosphere
  • entire atmospheric column

Data in GRIB2 format

NOTES:

  1. u (UGRD) and v (VGRD) components of the wind vector are to be resolved relative to the defined grid, in the direction of increasing i and j coordinates. Please refer to Code Table 7 of the GRIB standard for further details.
  2. Radiation fluxes parameters NLWRS_SFC, DSWRF_NTAT, and DLWRF_NTAT are encoded as accumulated values, as per value 4 of the Time Range Indicator (Code Table 5 of the GRIB format standard). This changes the unit from Watts per square metre to Joules per square meter.
  3. Specific Humidity (SPFH) is the model's native moisture variable. It should be used in all NWP applications. Dew point depression (DEPR) is a diagnostic parameter and is not meant for use in high-precision applications.