Figure 1.

North American winter temperature dipole (NAWTD): Observed composites of (a) near‐surface (2 m) temperature anomalies and (b) mid‐tropospheric (500mb) geopotential height anomalies for all historical (1980–2015) winter temperature dipole event occurrences defined using a 15% geographic area threshold. The eastern and western dipole regions are defined in Figure 1a, while the circulation analysis domain is outlined by the grey box in Figure 1b. Here we define a daily dipole event to be the co‐occurrence of (1) daily maximum temperatures over 15% or more of the western domain's land grid cells greater than their 84th percentile threshold and (2) daily minimum temperatures over 15% or more of the eastern domain's land grid cells less than their 16th percentile threshold.