Interannual variability of the North American cold air stream and associated synoptic circulations

Yuki Kanno, John E. Walsh, Toshiki Iwasaki

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

In boreal winter, the cold air mass (CAM) flux of air with a potential temperature below 280K forms climatological mean CAM streams in East Asia and North America (NA). This study diagnoses the interannual variability of theNAstream by an analysis of theCAMflux across 60°Nbetween Greenland and the Rocky Mountains. The first empirical orthogonal function (EOF) represents the variations in intensity of the NA stream. When the first principal component (PC1) is highly positive, the central part of the NA stream is intensified, with cold anomalies east of the Rocky Mountains. At the same time, a stratospheric polar vortex tends to split or displace toward NA. PC1 is highly correlated with the tropical Northern Hemisphere pattern, implying that this pattern is associated with the intensity of the NA stream. The second EOF shows a longitudinal shift of the NA stream toward Greenland or the Rocky Mountains. A highly negative PC2 results in a cold anomaly from western Canada to the Midwestern United States and anomalous heavy snowfall in the northeastern United States. PC2 is positively correlated with the Arctic Oscillation, which suggests that the longitudinal position of the NA stream varies with the Arctic Oscillation. These results illustrate how the intensity and location of cold air outbreaks vary with large-scale modes of atmospheric variability, with corresponding implications for the predictability of winter severity in NA.

Original languageEnglish
Pages (from-to)9575-9590
Number of pages16
JournalJournal of Climate
Volume30
Issue number23
DOIs
Publication statusPublished - 2017 Dec 1

Keywords

  • Airflow
  • Arctic Oscillation
  • Climate variability
  • Cold air surges
  • Cool season
  • Teleconnections

ASJC Scopus subject areas

  • Atmospheric Science

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