UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch Quantitative assessment of wind storms...
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Transcript of UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch Quantitative assessment of wind storms...
![Page 1: UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch Quantitative assessment of wind storms and extreme extra- tropical cyclones under climate.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649edc5503460f94becd99/html5/thumbnails/1.jpg)
UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Quantitative assessment of wind storms and extreme extra-tropical cyclones under climate
change
Gregor C. Leckebusch
Special Thanks to:
M. Donat, D. Renggli, T. Kruschke,
K. Nissen, P. Lorenz, T. Pardowitz, U. Ulbrich
Institute of Meteorology
Freie Universität Berlin, Germany
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
0) Outline
Introduction to extra-tropical cyclones
Gaussian and Lagrange Perspective of Cyclonic Activity
Recent climate conditions
Anthropogenic Climate Change
• Objective Wind Storm Identification • Extreme Value Analysis• Anthropogenic Climate Change
Summary
![Page 3: UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch Quantitative assessment of wind storms and extreme extra- tropical cyclones under climate.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649edc5503460f94becd99/html5/thumbnails/3.jpg)
UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
1. Introduction
Extra-tropical Cyclones: Crucial part of atmospheric circulation;Highly relevant for energy transports
Objective Measure of its strengths?How to deduce information about potential changes of these extreme events?Which processes influence the variability of cyclone occurrence?
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Cyclone & storm~Months ~Days
SST, NAO, snow
Growths factors for cyclones
latent heat Divergence
Baroclinicity
Adapted fromLutgens & Tarbuck (Eds., 2007) ECMWF Forecast for 20.05.2010 00 UTC
Geopotential 500 hPa
Potential Sources of Variability
~Decades
AMM, PNA, AMO, ENSO
~CentenialAnthropogenic Change
1. Introduction
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
MSLP: Stormtrack
Ulbrich et al., 2008 J. Climate
2. Gaussian Perspective
NCEP-NCAR, 1961-2000 23 AOGCM Ensemble
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Ulbrich, Pinto, Kupfer, Leckebusch, Spangehl, Reyers (2008), J Climate
1000 hPa Stormtrack: ACC-Signal (SRES A1B)
2. Gaussian Perspective
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
ERA40 Re-analysis: Track density Winter (ONDJFM), ALL Systems
Ensemble Mean: Track density Winter (ONDJFM), ALL Systems
Unit: Systems per winter
1961-2000
2. Lagrange Perspective: Cyclone Tracks
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
A1B Climate Change Signal All Systems
2. Lagrange Perspective: Cyclone Tracks
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Definition: Extreme Cyclone Systems
Systems with a Laplacian of MSLP ( )above the 95th percentile,
i.e. only the upper 5% of the distribution are recognised here
NCEP or ERA40 re-analysis: most of the historical relevant winter storms are included (as far as storms are resolved by re-analysis data)
2. Lagrange Perspective: Cyclone Tracks
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
A1B Climate Change Signal Strong Systems
Weighting via: W
Weight: W2
Weight: W4
For the region of e.g. NE Atlantic:ca. 10-20% increase
2. Lagrange Perspective: Cyclone Tracks
Leckebusch et al., 2008b
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Cyclone Intensity (Laplacian of MSLP) for ALL Systems:
2. Lagrange Perspective: Cyclone Tracks
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
European Storm Cyclones
ERA40, 1961-2000
Change Signal GCM-Ensemble
cyclone track density
intensity of storm cyclones
Max.Wind speed during storm days
(Donat, Leckebusch et al., 2010a)Isolines: Inter-model std.-dev
2. Lagrange Perspective: Cyclone Tracks
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Introduction of an objective Storm Severity Index (SSI) (cf. Leckebusch et al., 2008)
3
98
max, 1
)(
),(,0max
Ger
Ger
K
k
T
tkKT A
kv
tkvSSI
98th Percentile(ONDJFM)
m/s
Event Tracking: related to impacts
3. Wind storms: Identification
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
• Generalized Pareto Distribution
ξ : shapeσ : scaleμ : shift
Probability density function (pdf)
Containing 3 families of tail distributions• Rotated Weibull (with upper bound)
ξ < 0
• Gumbel (no bound, exponential decay of pdf) ξ = 0
• Fréchet (no upper bound, polynomial decay of pdf) ξ > 0
/1
1exp)(z
zG
e.g. Coles, An Introduction to Statistical Modeling of Extreme Values (2001)
)()( zGdz
dzg
3. Wind storms: 3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
All tracks are considered, which have at least one track point within the according region:
NORTH-EUROPE (NO-EU)
NORTH-WEST-EUROPE (NW-EU)
SOUTH-EUROPE (SO-EU)
NO
NW
SO
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Threshold selection:
On average 1 event per year and model:= 1024 storms
SSI threshold: 11.19
Percentage of events from single model contribution to the ensemble
Extreme value analysis: Ensemble composition and threshold
%
SSI-Threshold
Region: NW-EU
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Total numbers of events in each 30 year periodENSEMBLESMulti-model ensemble inA1B scenario
Region: NW-EU
Model composition for each 30 year period
Events: SSI > 11.19
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
2069-20981971-2000
Return Level of a 50-year EventRegion: NO-Europe
EVA:
stationary &non-stationary
model
ENSEMBLESMulti-model ensemble inA1B scenario
Region: NW-EU
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Region RL5 RL10 RL25 RL50 RL100
NO-EUROPE
+53% +59% +67% +73% +79%
NW-EUROPE
+13% +14% +15% +15% +16%
SO-EUROPE
-19% -27% -36% -43% -49%
Relative changes of Return Levels by 2098 compared to 1971
Trends (non-stationary model)
Red: statistical significant on 95% level
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
ECHAM5-OM1: 3x30 Years of 20C climate conditionsGermany !!!
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
2011-2040
2041-2070
2071-2100
Results based on 3 x 30 year simulation (ECHAM5-OM1) SRES A1B scenarioRegion: Germany
3. Wind storms: EVA
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UNESCO Extreme Meeting, Paris, 27.-29.9.2010 G.C. Leckebusch
Different methods to assess the potential anthropogenic changes in synoptic cyclone behaviour were applied or newly developed
Stormtrack: A 23 MME reveals significant increase at the downstream end of the climatological storm track over the North-Atlantic under ACC conditions
Cyclone tracks: ACC:
Reduction in the number of all cyclones on an hemispheric scale
Increase in frequency of severe cyclones in winter in certain “hotspots”, e.g. Northeast-Atlantic
Extreme Value Analysis identifies changes in the statistical properties of the frequency of severe wind storms
4. Summary