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- Title
Boreal Winter Extratropical Weather Regime Changes During 1979–2019 and Their Weather Impacts and Possible Linkages to Sea‐Ice in the Nordic Seas.
- Authors
Fan, Songmiao; Chen, Xiaodan; Cohen, Judah
- Abstract
Previous studies have suggested possible connections between the decreasing Arctic sea‐ice and long‐duration (>5 days, LD) cold weather events in Eurasia and North America. Here we document the occurrences of weather regimes in winter by their durations, based on the empirical orthogonal function analyses of the daily geopotential height fields at 500 hPa (z500) for the months of November–March 1979–2019. Significant changes in the occurrence frequency and persistence of Ural ridge (UR) and weak stratospheric polar vortex (PV) were found between winters following high and low autumn sea‐ice covers (SIC) in the Barents and Kara seas. It is shown that a strengthening of the UR is accompanied with a weakening of the PV, and a weak PV favors Greenland ridge (GR). Cold spells in East Asia persist for 5 more days after an LDUR. Cold spells from Canada to the U.S. occur 2–5 days after an LD Ural trough (UT) and are associated with a z500 anomaly dipole centered over Alaska (+) and Hudson Bay (−). Cold spells in the eastern U.S. occur 1–4 days after an LDGR due to circulations resembling the Pacific‐North America pattern. Increased occurrences of UR in winter are associated with a decreased eastward propagation of synoptic waves from the North Atlantic to Japan and the North Pacific. Plain Language Summary: Analyses of observations show more frequent occurrences of long‐duration events of Ural ridge (UR), Greenland ridge (GR) and weak polar vortex (PV) in winter tend to follow low autumn sea ice cover (SIC) in the Barents and Kara Seas, and less frequent for Ural trough (UT) and strong PV. Long‐duration UR (GR or UT) events are followed by cold snaps in East Asia (the eastern US or Canada). Long‐term natural or anthropogenic warming in the Arctic and decreasing autumn SIC may cause more frequent cold air outbreaks in East Asia and the eastern US in winter, but less in Canada. Key Points: The Ural ridge regime and weak polar vortex are more frequent and persistent following low autumn sea ice in the Nordic seasThe long‐duration Ural and Greenland ridge regimes are followed by cold snaps in East Asia and the eastern USCold anomalies occur more frequently in Canada with increasing occurrences of the long‐duration Ural trough regimes
- Subjects
EAST Asia; POLAR vortex; COLD waves (Meteorology); REGIME change; AUTUMN; WINTER; SEA ice; WEATHER
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 11, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039868