Underlying Science

    Linkage of the cold air outbreaks to stratospheric circulation variability

    Two way dynamic coupling mechanisms between the stratosphere and troposphere in the extratopics:

    (i) The systematic downward propagation of geopotential height and zonal wind anomalies in the extratropics;

    (Kodera and Kuroda 1990; Baldwin and Dunkerton 1999; Baldwin and Dunkerton 2001; Cai and Ren 2007; Ren and Cai 2007)

    (ii) The delayed feedbacks of the stratosphere to the upward propagation of tropospheric Rossby waves;

    (Hartley et al. 1998; Limpavusan and Hartmann 2000; Ambaum and Hoskins 2002; Polvani and Waugh 2004; Kuroda 2008)

    (iii) The downward control principle and with transient eddy feedbacks;

    (Haynes et al. 1991; Song and Robinson 2004)

    (iv) The reflection of planetary waves;

    (Perlwitz and Harnik 2003)

    (v) The invertibility principle of potential vorticity.

    (Hartley et al. 1998)