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The Bjerknes Centre is a collaboration on climate research, between the University of Bergen, Uni Research, the Institute of Marine Research, Nansen Environmental and Remote Sensing Centre.

The link between eddy-driven jet variability and weather regimes in the North Atlantic-European sector

Erica Madonna will give a seminar talk on November 6. She has worked for two years as a postdoc on the jetSTREAM project at GFI. She studied atmospheric and climate science at the ETH Zürich, Switzerland. She hold a PhD degree from ETH, where she analysed moist ascending air streams (warm conveyor belts) in extratropical cyclones. She did a short postdoc at the university of Bern, working on thunderstorms and hail before moving to Bergen in November 2015

Erica Madonna
Erica Madonna

Abstract:

This study reconciles two perspectives on wintertime atmospheric variability in the North Atlantic-European sector: the zonal-mean framework comprising three preferred locations of the eddy-driven jet (southern, central, northern), and the weather regime framework comprising four classical North Atlantic-European regimes (Atlantic ridge AR, zonal ZO, European/Scandinavian blocking BL, Greenland anticyclone GA). A k-means clustering algorithm is used to characterize the two-dimensional variability of the eddy-driven jet stream, defined by the lower tropospheric zonal wind in the ERA-Interim reanalysis.

The first three clusters capture the central jet and northern jet, along with a new mixed jet configuration; a fourth cluster is needed to recover the southern jet.  The mixed cluster represents a split or strongly tilted jet, neither of which is well described in the zonal-mean framework, and has a persistence of about one week, similar to the other clusters. Connections between the preferred jet locations and weather regimes are corroborated -- southern to GA, central to ZO, and northern to AR. In addition, the new mixed cluster is found to be linked to European/Scandinavian blocking, whose relation to the eddy-driven jet was previously unclear.

 

Arranged date for the seminar talk: Nov 06, 2017