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2017-01-26

The plate contains four maps: Annual Winds, March Winds, August Winds and Annual Maximum Wind Speed. For each of the first three maps the frequency of wind, the mean speed of wind, and the frequency of calms are shown. On all three maps the frequency scale is 1 millimetre equals 2 percent. These values are presented for 50 locations across Canada. The map on the annual maximum wind speed shows the annual maximum hourly wind speeds in kilometres per hour for 30 year return period. Various types of anemometers can be used to measure wind. In Canada, two types are used; both employ a set of rotating cups mounted on a mast to indicate wind speed and a weather vane to indicate direction. There are about 200 anemometers of each type in use at the present time. Most anemometers are mounted according to World Meteorological Organization standards, at a height of 10 metres above the effective terrain. That is to say, the anemometer would be 10 metres above ground level over grassland, and 10 metres above the tree tops in a heavily treed area. Some wind observations were taken in Canada as early as 1840. Hourly observations became very useful with the advent of aircraft, and stations…

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