Limitations

The meteorological datasets provided on this website were developed by the MOE Environmental Monitoring and Reporting Branch (EMRB) to assist all those involved in advanced air modelling in Ontario. Although care was put into the creation of these files, the Ministry cannot guarantee absolute accuracy. The Ministry may, at any time, change the datasets. The Ministry reserves the right to require a customized data set if local influences are believed to be significant for the analysis performed (i.e longer averaging times).

Redistribution

You are authorized to further distribute Ontario meteorological data, including any portion of it, contained on this website under the following conditions only:

• No fee will be charged explicitly to any party to whom it is distributed.
• Original (Unprocessed) meteorological files where obtained from Environment Canada. Environment Canada must be accredited as the source of the product. In the case of redistribution via the Internet, an approved Environment Canada logo is presented at the point of access to the product. Redistribution must occur so that any other party must agree to the same redistribution restrictions before use of the redistributed product is allowed. Please refer to http://www.smc.ec.gc.ca/climate/attachment1_e.cfm
• Processed data files were prepared by the Ontario Ministry of the Environment, Environmental Monitoring and Reporting Branch (EMRB). This data must be distributed in its original form.
• This document is to be provided when data is distributed

NOTE: The above applies only to the Ontario met data files. No portion of this website, www.webmet.com, may be reproduced in part or in whole, including images, content, or layout.

Regional Meteorological Data Sets

The Ministry has prepared regional meteorological data sets. The surface meteorological sites used were Toronto (Pearson Airport), London, Sudbury and Ottawa along with International Falls, MN and Massena, NY. The following meteorological elements were used in AERMET processing for the 5 year period from 1996 to 2000: ceiling height, wind speed, wind direction, air temperature, total cloud opacity and total cloud amount.

The upper air stations used were Maniwaki, QU, White Lake, MI, Buffalo, NY, Albany, NY and International Falls, MN. Table 1 gives the locations of the surface meteorological sites and lists the upper air station used for each site. The locations of the upper air sites are given in Table 2.

Table1. Surface meteorological sites location and upper air stations to use.

Table 2. The location of upper air sites

The surface meteorological data was preprocessed to give a minimum wind speed of about 1 m/s and to reduce the amount of missing data. The preprocessing steps were:

• Treatment of Wind Speed and Direction for "calm" conditions.
  
  For all "calm" conditions (where the wind speed and wind direction are equal to zero) the wind direction is set to a "missing" value. Hours with calm or very low wind speeds were set to minimum speeds as follows:
  
  If the wind speed is less then 4 km/h (for Canadian sites) it is set to 4 km/h.
  If the wind speed is less then 2 knots for International Falls, MN it is set to 2 knots.
  If the wind speed is less then 3 knots for Massena, NY it is set to 2 knots (Note a large percentage of calm winds are in the Massena data because of the comparatively high minimum wind speed).



• Interpolation of missing values.
  
  For each meteorological element linear interpolation was applied if the number of the missing hours is up to six in a row. Missing data at the very beginning and at the very end of the data set are left as "missing" (no extrapolation is applied). If the number of consecutive hours with missing values for the element is more then 6, the values are left as "missing".



• Units conversion.
  
  All units for Canadian sites were converted to the US standard required for AERMET input.



• Large percentage of missing data or non-operational hours treatment
  
  Even with the above processing, a surface station could still be missing a substantial amount of data. This could occur because the station either was not operated 24 hours a day or there were very many consecutive calm/missing hours in the original data set. If the surface station was operational for 18 hours or less per day or there were still more than 5% missing data after the above processing then missing data were filled using data from the nearest fully operational station located in similar geographic conditions.
  
  Although all 6 of the surface stations used to produce the regional meteorological data sets were operated 24 hours a day, the Massena data included about 20% calm conditions and 5% missing data. After processing through step 1 and 2 given above, there was still 14% missing data. Data from Montreal (Dorval Airport) were used to fill in these missing data.

AERMET Processing

Regional meteorological datasets are generated in AERMET, stage3 processing step, using different wind independent surface conditions, called "URBAN", "FOREST", "CROPS". It is assumed that surface conditions are the weighted average over a radius of 3 km from the facility in all directions. The surface conditions needed are the albedo (A), the Bowen ratio (Bo) and the surface roughness (Zo). The parameter values in Tables 3, 4 and 5 below were derived from data in Tables 4.1, 4.2b and 4.3 of the AERMET User's Guide.

"URBAN" - all surface parameters are set to urban values, as in Table 3.

Table 3. URBAN surface conditions.

"FOREST" - all surface parameters are set to the mixture of coniferous and deciduous forests in the ratio 50%/50% as in Table 4.

Table 4. FOREST surface conditions

"CROPS" - all surface parameters are set to the mixture of Grassland, Cultivated Land, Coniferous and Deciduous forest in the ratio: 45%/45%/5%/5% as in Table 5.

Table 5. CROPS surface conditions

Geographic Application of the Regional Meteorological Data Sets

The application of the regional meteorological data sets across Ontario is described in Table 6. This table lists the MOE region and districts for which each of the meteorological data sets is most applicable. Figure 1 provides a graphical representation of the geographic application of these regional data sets.

Table 6 Application of regional meteorological data sets for MOE regions and districts.