Recent amplification of the North American winter temperature dipole. Issue 17 (1st September 2016)

• Record Type: Journal Article
• Authors: Singh, Deepti; Swain, Daniel L.; Mankin, Justin S.; Horton, Daniel E.; Thomas, Leif N.; Rajaratnam, Bala; Diffenbaugh, Noah S.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 17(2016)
• Page Start: 9911
• Page End: 9928
• Publication Date: 2016-09-01
• Subjects: climate change detection -- climate change impacts -- extreme event attribution -- atmospheric dynamics; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2016JD025116
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: During the winters of 2013–2014 and 2014–2015, anomalously warm temperatures in western North America and anomalously cool temperatures in eastern North America resulted in substantial human and environmental impacts. Motivated by the impacts of these concurrent temperature extremes and the intrinsic atmospheric linkage between weather conditions in the western and eastern United States, we investigate the occurrence of concurrent "warm‐West/cool‐East" surface temperature anomalies, which we call the "North American winter temperature dipole." We find that, historically, warm‐West/cool‐East dipole conditions have been associated with anomalous mid‐tropospheric ridging over western North America and downstream troughing over eastern North America. We also find that the occurrence and severity of warm‐West/cool‐East events have increased significantly between 1980 and 2015, driven largely by an increase in the frequency with which high‐amplitude "ridge‐trough" wave patterns result in simultaneous severe temperature conditions in both the West and East. Using a large single‐model ensemble of climate simulations, we show that the observed positive trend in the warm‐West/cool‐East events is attributable to historical anthropogenic emissions including greenhouse gases, but that the co‐occurrence of extreme western warmth and eastern cold will likely decrease in the future as winter temperatures warm dramatically across the continent, thereby reducing the occurrence of severely cold conditions in the East. Although our analysis is focused on one particular region, our analysis framework is generally transferable to the physical conditions shaping different types of extreme events around the globe. Key Points: U.S. warm‐West/cool‐East dipole events associated with large circulation anomalies across the Northern Hemisphere mid‐latitudes Historical increase in dipole events linked to increasing frequency of events when associated circulation patterns occur Positive trend in dipole events attributable to historical anthropogenic warming, though future warming is likely to reverse trend