Isentropic analysis of polar cold airmass streams in the Northern Hemispheric winter

Toshiki Iwasaki, Takamichi Shoji, Yuki Kanno, Masahiro Sawada, Masashi Ujiie, Koutarou Takaya

Research output: Contribution to journalArticlepeer-review

64 Citations (Scopus)


An analysis method is proposed for polar cold airmass streams from generation to disappearance. It designates a threshold potential temperature θT at around the turning point of the extratropical direct (ETD) meridional circulation from downward to equatorward in the mass-weighted isentropic zonal mean (MIM) and clarifies the geographical distributions of the cold air mass, the negative heat content (NHC), their horizontal fluxes, and their diabatic change rates on the basis of conservation relations of the air mass and thermodynamic energy. In the Northern Hemispheric winter, the polar cold air mass below θT = 280 K has two main streams: the East Asian stream and the North American stream. The former grows over the northern part of the Eurasian continent, flows eastward, turns down southeastward toward East Asia via Siberia, and disappears over the western North Pacific Ocean. The latter grows over the Arctic Ocean, flows toward the eastern coast of North America via Hudson Bay, and disappears over the western North Atlantic Ocean. In their exit regions, wave-mean flow interactions are considered to transfer the angular momentum from the cold airstreams to the upward Eliassen-Palm flux and convert the available potential energy to wave energy.

Original languageEnglish
Pages (from-to)2230-2243
Number of pages14
JournalJournal of the Atmospheric Sciences
Issue number6
Publication statusPublished - 2014 Jun


  • Angular momentum
  • Climate classification/regimes
  • Cold air surges
  • Dynamics
  • Meridional overturning circulation
  • Planetary waves

ASJC Scopus subject areas

  • Atmospheric Science


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