AGRICULTURAL METEOROLOGY: SOME CHARACTERISTICS OF AIR TEMPERATURE IN ALBERTA AND SASKATCHEWAN

Abstract

A five-year moving average of mean temperature for the period April 1 to August 31 has a range of variation of about 4° F. over the years 1893–1933 at Edmonton and Calgary (central and southern Alberta), and Battleford and Swift Current (central and southern Saskatchewan). The general trend over the 41 years is slightly upward at the last three stations; there are also shorter irregular cycles of above- and below-average values of both mean temperature and mean daily range at all four stations. Short-term fluctuations of the former are most pronounced in April and May; those of the latter are equally in evidence in all five months. The annual averages of daily mean temperature (April 1–August 31) tend at all four stations to fall more frequently above than below the general average for the 41 years. Annual variation in monthly mean temperature is greatest in April and least in July, but the mean daily range is as variable for the summer as for the spring months. There is a fairly close correlation between the annual variations in mean monthly temperature at the four stations, but no significant association between the mean temperature of successive months at the same station. Below-average monthly temperatures tend to be associated with above-average precipitation, particularly in July and August.During 1916–1933, the intra-monthly variation of both daily maximum and minimum is greatest in April and least in July and August. Within any of the five months, the daily maxima are more variable than the minima. There is a significant correlation between the daily maxima and minima within months (which however diminishes progressively from April to August), and between the mean maximum and mean minimum of April, May and August in different years. The frequency distributions of the 18 years' daily maxima and minima have individual characteristics for each of the five months, which show a generally similar seasonal trend at the four stations. Seasonal trend in the daily range is much less than that in the mean temperature.The hourly temperature at Swift Current, averaged over four years, attains its maximum at 3 p.m. in all five months studied. The hour of average minimum varies from 6 a.m. in April to 4 a.m. in June. In each month the hours with below-average are in excess of those with above-average temperatures, but this inequality is more pronounced in spring than in summer. The mean of the daily maximum and minimum may sometimes deviate considerably from the mean of the 24 hourly observations.