Canada's Chinook Belt

Abstract

The chinook is the best example of the family of mountain winds that blows in regions where long mountain chains lie more or less at right angles to the prevailing wind. Apart from the unseasonable warmth it brings to Canada's interior in winter, it represents an efficient system through which latent heat drawn from the Pacific coast is converted into sensible heat and transported zonally across the continent. It also compromises both the physical and human environments. The severity of impacts depends on either the amount of anomalous warming experienced or on the number of chinook events occurring over a winter, and often on both. In Canada, the chinook belt lies almost exclusively in southern Alberta. In this paper, the belt is described and mapped with respect to the strength of the wind's temperature signal and numerical frequency. The temperature signal (the signal) is the difference between the highest temperature attained during a chinook event and the daily maximum. The frequency is the number of days in the winter with, at least, 1 h of chinook wind. Mean point values of the signal range from 13 to 25 K. Mean seasonal frequency varies from 43 days to 52 days per winter. The core of the belt for temperature and frequency do not coincide. The highest frequencies occur in the Crowsnest Pass area whereas the strongest signals are found further east of the mountains in an axis that includes Vauxhall and Brooks. Both signal strengths and frequency show strong decadal variations. The 1980s were chinook rich; the 1970s were chinook poor.

Spatial and temporal variability of soil freeze-thaw cycling across Southern Alberta, Canada

“…Figure 5 shows significant spatial variability in the correlation between maximum air temperature and wind speed. The various fitted spline surfaces of this correlation pattern of climate-soil variability reveal a similar spatial pattern to the observed regional pattern of Alberta's Chinook signal from 1951-1990 [13]. The similar spatial pattern between Alberta's average Chinook signal and the maximum air temperature and wind speed correlation surface supports the idea that a Table 5.…”

“…A notable significant interaction term in the winter model was maximum air temperature, minimum air temperature and wind speed (p < 0.05), this interaction had a positive influence on soil temperature. The maximum, minimum air temperature and wind speed interaction may be capturing the Chinook events; these events can increase daily maximum, minimum air temperatures associated with high wind speed [13]. The specific interaction terms that may be related to long term synoptic climate events, such as teleconnections nonetheless require more investigation as the complex nature of how teleconnections influence climate and freeze-thaw events over large areas.…”

“…Chinook winds belong to a family of mountain winds that blow in regions where long mountain chains are more or less perpendicular to the prevailing wind. Chinooks are established when moist Pacific air is blown westward by prevailing winds [13]. As the air mass cools, it then rises over the Rocky Mountains of British Columbia.…”

“…The moist air mass condenses and precipitates over the mountain ranges. The drier Pacific air mass reaches the leeward side of the mountains and warms at the dry adiabatic lapse rate as it descends onto the prairies with high wind speeds [13]. The warm moisture-deprived air has the ability to quickly melt and evaporate any snow cover, while thawing the upper layers of the soil.…”

Daily temperature records from a mesonet in the foothills of the Canadian Rocky Mountains, 2005–2010

“…Nkemdirim (1996) created monthly regression equations using closely-correlated stations to recreate daily minimum and maximum temperatures in southern Alberta. Eischeid and Pasteris (2000) used between one and 20 four most closely correlated neighbouring stations to estimate daily minimum and maximum temperatures for the western United States, using a version of the general linear least squares regression estimation -least absolute deviations criteria.…”