Trends and Variability of North Pacific Polar Lows

Abstract

The6-hourly 1948–2010NCEP 1 reanalyses have been dynamically downscaled for the region of theNorth Pacific.With a detectingand- tracking algorithm, the climatology of North Pacific Polar Lows has been constructed. This derived 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 small positive trend. A canonical correlation analysis describes the conditioning of the formation of Polar Lows by characteristic seasonal mean flow regimes, which favor, or limit, cold air outbreaks and upper air troughs.