Wind and Sunshine

Contained within the 3rd Edition (1957) of the Atlas of Canada is a plate consisting of four maps, two showing wind and two showing sunshine. On the wind maps, the percentage frequency of the wind for winter and summer from each direction is represented by means of wind roses. Wind roses show wind direction and percentage frequency by means of lines proportional in length to the percentage frequency that extend out in the direction from which the wind blows. The percentage of calms is indicated by the figure in the centre of the station circle. The lower maps show the mean annual total hours of bright sunshine. The data these maps were based on is the mean annual percentage of total daylight hours (sunrise to sunset) with bright sunshine calculated from an accumulation of the mean monthly totals for twelve months at some 125 stations across Canada. All available data have been used; the length of record at most stations is between 20 and 50 years. To obtain values representing the mean annual percentage of daylight hours with bright sunshine, the total hours of bright sunshine were divided by the accumulated total number of hours from sunrise to sunset during the year. The inset table shows the times of sunrise, sunset and average hours of sunlight for various latitudes on June 21st and December 22nd (the longest and shortest days of the year).