The structure and large-scale organization of extreme cold waves over the conterminous United States
The study identifies three recurrent extreme cold wave (ECW) patterns that affect the upper midwest, northwest and southeast US, respectively, and assesses how each patterns is linked to the larger-scale atmospheric circulation and key modes of climate variability. The ability of modern climate models to represent ECW behavior and forcing is also tested.
The research provides an objective basis for understanding how and why certain extreme weather events occur. This basis provides critical metrics for assessing (a) the veracity of modern climate models and (b) how the behavior of such extreme weather events may vary in future decades.
An hierarchical cluster analysis of daily surface air temperature is used to isolate canonical extreme cold wave (ECW) patterns for the boreal cool season in both observations and a parallel CCSM4 simulation over the US during the period 1950-2005. The large-scale meteorological pattern (LMP) that induces each of the observed ECWs is isolated. Statistical and synoptic analyses of observed and simulated ECWs and LMPs are carried out to test the CCSM4’s ability to properly simulate ECWs. ECW modulation by key climate modes (ENSO; PDO) and surface cryospheric perturbations is assessed.