A long-term climatology of North Atlantic polar lows

Abstract

A dynamical downscaling of the 6-hourly 1948–2006 NCEP/NCAR re-analyses for the subarctic region of the North Atlantic has been used to derive a climatology of polar lows by means of a tracking algorithm based on the simulated bandpass filtered MSLP-fields. This climatology is consistent with the limited observational evidence in terms of frequency and spatial distribution. The climatology exhibits strong year-to-year variability but weak decadal variability and a negligible trend. A Canonical Correlation Analysis describes the conditioning of the formation of polar lows by characteristic meridional seasonal mean flow regimes, which favor cold air outbreaks and upper air troughs.