Quantifying the relevance of atmospheric blocking for co-located temperature extremes in the Northern Hemisphere on (sub-)daily time scales

Atmospheric blocking can influence near-surface temperature via circulation and radiative forcing. This study investigates the relevance of blocking for co-located (sub-)daily temperature extremes and the spatial variability of this relationship in the Northern Hemisphere. It is shown that over large parts of the high-latitude continents warm temperature extremes often occur simultaneously with atmospheric blocking at the same location. Taking also weak blocks into account, more than 80% of the six-hourly warm extremes are associated with blocking, e.g., in eastern Canada, Scandinavia and parts of Siberia. On the contrary, cold extremes typically are not related to co-located atmospheric blocking. This difference between warm and cold extremes points to differences also in the physical driving mechanisms of the extremes. The strong linkage of warm temperature extremes and blocking should be considered when investigating changes of temperature extremes with global warming. Citation: Pfahl, S., and H. Wernli (2012), Quantifying the relevance of atmospheric blocking for co-located temperature extremes in the Northern Hemisphere on (sub-)daily time scales, Geophys. Res. Lett., 39, L12807, doi:10.1029/2012GL052261.