The role of stratosphere-troposphere coupling in the occurrence of extreme winter cold spells over northern Europe

Lorenzo Tomassini, Edwin Gerber, Mark P. Baldwin, Felix Bunzel, Marco Giorgetta

Research output: Contribution to journalArticle

Abstract

Extreme cold spells over Northern Europe during winter are examined in order to address the question to what degree and in which ways stratospheric dynamics may influence the state of the troposphere. The study is based on 500 years of a pre-industrial control simulation with a comprehensive global climate model which well resolves the stratosphere, the MPI Earth System Model. Geopotential height anomalies leading to cold air outbreaks leave imprints throughout the atmosphere including the middle and lower stratosphere. A significant connection between tropospheric winter cold spells over Northern Europe and erosion of the stratospheric polar vortex is detected up to 30hPa. In about 40 percent of the cases, the extreme cold spells are preceded by dynamical disturbances in the stratosphere. The strong warmings associated with the deceleration of the stratospheric jet cause the tropopause height to decrease over high latitudes. The compression of the tropospheric column below favors the development of high pressure anomalies and blocking signatures over polar regions. This in turn leads to the advection of cold air towards Northern Europe and the establishment of a negative annular mode pattern in the troposphere. Anomalies in the residual mean meridional circulation during the stratospheric weak vortex events contribute to the warming of the lower stratosphere, but are not key in the mechanism through which the stratosphere impacts the troposphere.

Original languageEnglish (US)
Article numberM00A03
JournalJournal of Advances in Modeling Earth Systems
Volume4
Issue number10
DOIs
StatePublished - 2012

Fingerprint

Upper atmosphere
Troposphere
stratosphere
troposphere
winter
cold air
anomaly
warming
polar vortex
meridional circulation
tropopause
geopotential
polar region
Vortex flow
vortex
global climate
climate modeling
advection
compression
Europe

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Environmental Chemistry
  • Global and Planetary Change

Cite this

The role of stratosphere-troposphere coupling in the occurrence of extreme winter cold spells over northern Europe. / Tomassini, Lorenzo; Gerber, Edwin; Baldwin, Mark P.; Bunzel, Felix; Giorgetta, Marco.

In: Journal of Advances in Modeling Earth Systems, Vol. 4, No. 10, M00A03, 2012.

Research output: Contribution to journalArticle

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