Troposphere‐stratosphere dynamic coupling under strong and weak polar vortex conditions

The relationship between Northern Hemisphere (NH) tropospheric and stratospheric wave‐like anomalies of spherical zonal wave number (ZWN) 1 is studied by applying Canonical Correlation Analysis (CCA). A lag‐correlation technique is used with 10‐day lowpass filtered daily time series of 50‐ and 500‐hPa geopotential heights. Generally stratospheric circulation is determined by ultralong tropospheric planetary waves. During winter seasons characterized either by an anomalously strong or weak polar winter vortex different propagation characteristics for waves of ZWN 1 are observed. The non‐linear perspective of the results have implications for medium range weather forecast and climate sensitivity experiments.