Low-Frequency Rotation of Surface Winds over Canada

Abstract

Hourly surface observations from the Canadian Weather Energy and Engineering Dataset were analyzed with respect to long-term wind direction drift or rotation. Most of the Canadian landmass, including the High Arctic, exhibits a spatially consistent and remarkably steady anticyclonic rotation of wind direction. The period of anticyclonic rotation recorded at 144 out of 149 Canadian meteostations directly correlated with latitude and ranged from 7 days at Medicine Hat (50°N, 110°W) to 25 days at Resolute (75°N, 95°W). Only five locations in the vicinity of the Rocky Mountains and Pacific Coast were found to obey a “negative” (i.e., cyclonic) rotation. The observed anticyclonic rotation appears to be a deterministic, virtually ubiquitous, and highly persistent feature of continental surface wind. These findings are directly applicable to probabilistic assessments of airborne pollutants.

Keywords

• low frequency variability
• surface observations
• wind direction