A Wind Chill Climatology of North America: Decadal and Regional Trends

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Wednesday, 7 January 2015
Macy E. Howarth, Hobart and William Smith Colleges, Geneva, NY; and M. Brackett and N. F. Laird

Extreme wind chill temperatures (WCTs) can pose a significant risk to people, agriculture, and livestock. WCT has previously been investigated for few areas in the United States (e.g., Central Plains) and regions around the world (e.g., Patagonia, Greece), but not at a continental scale. This project examines regional differences and decadal trends in WCTs across North America to understand how changes in climate conditions have influenced extreme winter weather environments. Data was used from 160 hourly reporting surface stations that included at least 70% of hourly observations for the winters (DJF) of 1980/1981 through 2013/2014. Analyses show the coldest 1% of WCTs generally warmed during the last several decades, especially in northern and western Canada, as well as central and northwestern United States, with minimal changes in coastal regions. The most substantial decadal warming of extreme WCTs occurred from the 1990s to 2000s. In addition, the frequency of extreme WCTs has decreased, again largely in northern Canada and the central United States. However, mean temperature and mean WCT during the time period studied do not exhibit substantial warming. These findings suggest that the largest changes in climate across North America during the winter months have been limited to specific regions since 1980 and may be a result of changes in intensity and/or frequency of extreme Cold Air Outbreaks.