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 [email protected]
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)
EMS, 14.09.2012 [email protected]
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
EMS, 14.09.2012 [email protected] 12Winter 1981-2010 compared to 1901-2010
• 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 [email protected] 15
W (VGc) 1901-2010
W (VGc) 1981-2010
W (VGc) Difference
Spare: Change Signal by Region
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