Trends and Variability of North Pacific Polar Lows

Abstract

The 6-hourly 1948–2010 NCEP 1 reanalyses have been dynamically downscaled for the region of the North Pacific. With a detecting-and-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.

An objective global climatology of polar lows based on reanalysis data

“…The seasonal distribution of PLs in the North Pacific is in general in good agreement with the distribution presented by Chen and von Storch (). The PL season in the Northwest Pacific and the North Atlantic are comparable, except for considerably fewer PL occurrences in the former region in March.…”

“…The spatial distribution of the climatologies in the NH between the two reanalyses shows similar patterns. They are in good agreement with that presented for the North Atlantic by Zahn and von Storch (), and for the North Pacific by Chen and von Storch (), even though different methodologies are used.…”

“…Using a different approach, Zahn and von Storch (2008) created a PL climatology for the North Atlantic sector for the years 1948-2006 by downscaling the global NCEP/NCAR reanalysis with a regional climate model with a resolution of about 50 km. Chen and von Storch (2013) applied the same methodology for the North Pacific sector for the years 1948-2010.…”

State and Perspectives of the Concept of Large‐Scale Conditioning of Regional Climate Modelling

“…A first case was Polar Lows in the North Atlantic and North Pacific (Chen et al, 2012;Chen and von Storch, 2013). These relatively small energetic storms form over the subarctic sea, mostly in cold air outbreaks and can be identified well only since the advents of satellites.…”

“…A climatology of Polar Lows in the North Atlantic was obtained by implementing this method , and later of Polar Lows in the North Pacific (Chen and von Storch, 2013), of Medicanes in the Mediterranean Sea (Cavicchia et al, 2014a), and of Coastal Low Level Jets in the Bohai / Yellow sea region (Li et al, 2018). The methodology has matured now and is routinely used in many applications -mainly for deriving atmospheric states in the past decades.…”