Cold and hot periods associated with dry conditions over the Canadian prairies

Abstract

Dry conditions and droughts are a normal feature of the Canadian Prairie climate. A common perception is that these periods of below-normal precipitation are always associated with above-average temperatures. Using a core region centred near Edmonton Alberta, this study incorporates gridded temperature and precipitation information for the period 1900-2009 to quantify how often cold, as well as hot, dry conditions occurred. Shorter-term records of atmospheric circulation, upper-air soundings and surface cloud-related variables are then used to examine some of the factors leading to these conditions. Using drought criteria based on the Standardized Precipitation Index, 15 month-long anomalously cold, dry periods were identified; this is about an order of magnitude less than the number of hot, dry periods. Cold periods generally occurred in the late spring and occurred within some of the major droughts affecting the region. The cold periods were linked with the advection of cold, dry air from the north, whereas hot periods were somewhat attributable to air descending the eastern flank of the Western Cordillera. To understand drought fully, all conditions leading to the persistent lack of precipitation need to be considered including those instances with cold temperatures.