TU Bergakademie Freiberg , Brennhausgasse 14, 09596 Freiberg, GermanyPhone: 0 37 31/39-3533, www.tu-freiberg.de

Effects of atmospheric circulation on air temperature in Europe and northern Asia

Andreas Hoy, Mait Sepp, Jörg Matschullatandreas.hoy@ioez.tu-freiberg.de

Outline of Research Context• Large increase of air temperature in Europe and northern Asia

(Siberia) within 1901-2010 – particularly visible in winter, amplified in recent climate normal (1981-2010)

• Regionally diverse warming (cooling) patterns cannot be explained by „global warming“ alone

• Warming in most (European) circulation forms (Jones/Lister 2009) if most of them warm, additional warming should be connected to changes in their distribution

• Objectives:1. To illustrate changes in circulation type frequency2. To investigate the spatial impact of more/less frequent

circulation types on air temperature3. To define regions mostly affected by circulation changes

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Basics: Classifications

1. Vangengeim-Girs classification (VGc) • Hemispheric-scale approach (here: using

of North Atlantic-Eurasian sector)• Three main circulation types (W, E, C)• Large frequency fluctuations, “objective”

verification using NAOi

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WC

E

Anissimov et al. 2010

2. Grosswetterlagen classification (GWLc)• Continental-scale approach (North Atlantic-European realm)• 29 sub-types (Grosswetterlagen), combinable into larger groups• Verification by automated version (SynopVis Grosswetterlagen,

SVGc, James 2012)

Basics: Mapping

• Analysis of daily data (circulation types and air temperature)• TEMP data: gridded set of daily averages in ~1.9 x 1.9° worldwide

resolution (Twentieth Century Global Reanalysis dataset)• Calculation of daily air temperature anomalies per grid point for

1901-2010/1981-2010; consideration of annual cycle)• Visualisation of average temperature anomaly fields per

circulation type (via mapping program SURFER)

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Results: Frequency Changes• Large changes in zonal air flow: strong increase of

westerlies/decrease of easterlies (1981-2010 vs. 1901-2010);

• Comparably small/ambiguous changes in meridional air flow

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Grosswetterlagen (GWLc/SVGc)Vangengeim-Girs (VGc), NAOi

• W, positive NAOi: westerly inflow into most of Europe• W#: westerly/north-westerly, E#: easterly/south-easterly inflow into Central E.)

Results: Air Pressure Maps – Westerlies

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• Sea level pressure patterns; centres of action

W (VGc)

L

H

NAOi +

L

H

W# (GWLc)

L

H

W# (SVGc)

L

H

Results: Temperature Signals – Westerlies

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H

L

W (VGc)

L

H

NAOi +

Results: Temperature Signals – Westerlies

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H

L

W# (GWLc)

L

H

W# (SVGc)

Results: Air Pressure Maps – Easterlies

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L

H

E# (GWLc)

H

L

E (VGc)

L

H

E# (SVGc)

HL

NAOi -

• Sea level pressure patterns, centres of action

Results: Temperature Signals – Easterlies

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H

L

E (VGc)

L H

NAOi -

Results: Temperature Signals – Easterlies

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H

L

E# (GWLc)

L

H

E# (SVGc)

Results: Temperature Changes and Circulation

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• Strong warming in Russia/moderate warming in Western and Central Europe in agreement to increasing westerlies (warm)/ decreasing easterlies (cold)

• Regional cooling in Greenland/ eastern Mediterranean connected to rather northerly inflow during westerlies

Conclusions

• Distinct impact of atmospheric circulation on air temperature changes in circulation type frequency naturally lead to changes in average air temperature

• In winter, westerlies largely increased/easterlies largely decreased in European/northern Asian realm

• Besides general warming, frequency shifts agree with large-scale warming pattern in most of northern/central Eurasia

• Regional (weak) cooling fits very well to detected frequency shifts

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W (VGc)

C (VGc)

W# (GWLc)

N# (GWLc)

Spare: Centres of Action

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E (VGc)

NAOi

E# (GWLc)

S# (GWLc)

Spare: Signal Stability (December)

PhD-Project Andreas Hoy andreas.hoy@ioez.tu-freiberg.de 15

W (VGc) 1901-2010

W (VGc) 1981-2010

W (VGc) Difference

Spare: Change Signal by Region

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