Download Folie 1 - Hans von Storch

Storminess in N Europe and E Canada
Hans von Storch
Institute for Coastal Research, GKSS Research Center, Germany
and KlimaCampus Hamburg, Germany
28-30 January 2008 - IDAG Spring Meeting, Boulder, Colorado
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N Europe storminess
Relevant publications
Schmidt, H. and H. von Storch, 1993: German Bight storms analyzed. - Nature 365, 791
Alexandersson, H., T. Schmith, K. Iden and H. Tuomenvirta, 1998: Long-term trend variations of
the storm climate over NW Europe. The Global Atmos. Oc. System 6, 97-120
WASA, 1998: Changing waves and storms in the Northeast Atlantic? - Bull. Amer. Met. Soc. 79,
741-760
Bärring, L. and H. von Storch, 2004: Northern European Storminess since about 1800. Geophys.
Res. Letters 31, L20202, doi:10.1029/2004GL020441, 1-4
Rockel, B., and K. Woth, 2007: Future changes in near surface wind extremes over Europe from an
ensemble of RCM simulations. Climate Change, 10.1007/s10584-006-9227-y
Matulla, C., W. Schöner, H. Alexandersson, H. von Storch, and X.L. Wang, 2007: European
Storminess: Late 19th Century to Present, Climate Dynamics DOI 10.1007/s00382-007-0333-y
The BACC author team, 2008: Assessment of Climate Change in the Baltic Sea Basin, Springer
Verlag Berlin - Heidelberg; ISBN 978-3-540-72785, 473 pp
von Storch, H., and R. Weisse, 2008: Regional storm climate and related marine hazards in the
Northeast Atlantic, In Diaz, H.F. and Murnane, R.J. (eds.), Climate Extremes and Society,
Cambridge: Cambridge University Press (in press)
Matulla, C., and H. von Storch, 2008: Changes in Eastern Canadian Storminess since 1880.
submitted
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Challenge
Storminess best represented by wind statistics, possibly
derived quantities such as stream function, vorticity, but
wind time series are almost always
• inhomogeneous
• too short
No robust link to level temperature, but to pattern of
seasonally mean air pressure.
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Example of inhomogeneities
in wind records
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Damages and storms
May 2006 meeting of scientists and re-insurances (Munich Re)
Consensus statement:
„1. Climate change is real, and has a significant human component related
to greenhouse gases.
2.
Direct economic losses of global disasters have increased in
recent decades with particularly large increases since the 1980s.
8.
Analyses of long-term records of disaster losses indicate that societal
change and economic development are the principal factors responsible for
the documented increasing losses to date.
9.
The vulnerability of communities to natural disasters is determined by
their economic development and other social characteristics.
10. There is evidence that changing patterns of extreme events are
drivers for recent increases in global losses.
13. In the near future the quantitative link (attribution) of trends in storm
and flood losses to climate changes related to GHG emissions is unlikely to
be answered unequivocally.“
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Pressure based proxies
Air pressure readings are usually homogenous
Annual/seasonal percentiles of geostrophic wind derived from
triangles of pressure readings (e.g., 95 or 99%iles); such
percentiles of geostrophic wind and of “real” wind are linearly
related.
Annual frequency of events with geostrophic wind equal or larger than
25 m/s
Annual frequency of 24 hourly local pressure change of 16 hPa in a
year
Annual frequency of pressure readings less than 980 hPa in a year
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Other storm proxies
Variance of local water levels relative to annual mean
(high tide) water level.
Repair costs of dikes
in historical times.
Sailing times of ships
on historical routes.
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N Europe
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Geostropic wind stats N Europe
Relevant publications
99%iles of annual
geostrophic wind speeds
for a series of station
triangles in the North Sea
regions and in the Baltic
Sea region.
Alexandersson et al., 2002
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Local pressure stats since 1800
Stockholm
Relevant publications
Lund
Time series of pressure-based storminess indices derived from pressure readings in Lund (blue) and
Stockholm (red). From top to bottom: Annual number of pressure observations below 980 hPa (Np980),
annual number of absolute pressure differences exceeding 16 hPa/12 h (NDp/Dt),
Intra-annual 95-percentile and 99-percentile of the pressure differences (P95 and P99) in units of hPa.
From Bärring and von Storch, 2005: see also BACC 2008.
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N + C Europe
Matulla, C., W. Schöner, H. Alexandersson, H. von Storch, and X.L. Wang, 2007: European
Storminess: Late 19th Century to Present, Climate Dynamics DOI 10.1007/s00382-007-0333-y
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Geostrophic stats
normalized
21 year Gaussian filtered
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24 hr pressure change stats
normalized
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E Canada +
Grønland
Matulla, C., and H. von Storch, 2008: Changes in Eastern Canadian Storminess since 1880. submitted
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E Canadian stations available
more
less
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Direct estimates
Subarctic
Arctic
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Regressing seasonal mean SLP on
low pressure percentiles
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Reconstructing past
low pressure percentiles
Subarctic
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Arctic
Conclusion
1. Monitoring extra-tropical storminess may be based on air
pressure proxies.
2. This allows assessments for 100 and more years.
3. Decades long upward and downwards trends have been
detected in recent years.
4. These trends are not sustained and have show recent
reversals in all considered regions.
5. Recent trends are not beyond the range of natural
variations, as given by the historical past, but are more of
intermittent character. Regional temperatures rose
significantly at the same time.
6. In E Canada, there seems some phase reversal between the
Arctic and Subarctic region.
7. In N Europe the present absence of a detectable signal is
consistent with RCM simulations.
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Reserve
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Stormcount 1958-2001
t≥T
Change of # Bft 8/year
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Weisse et al., J. Climate, 2005
publications
tRelevant
≤T
Warming and Storms in the N Atlantic
Fischer-Bruns et al., 2005
(11-yr running means)
NH Temp & NA storm count:
No obvious correlation in simulated historical times
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Hamburg – Storm surges
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Inhomogeneity
Inhomogeneity
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Regionale Entwicklung der
Temperatur und Sturmtätigkeit
11) Temperaturen in
Norddeutschland sind in
den letzten Jahrzehnten
gestiegen.
Sturmtätigkeit hat von
Jahrzehnt zu Jahrzehnt
geschwankt, aber auf
längere Sicht fast
unverändert seit 1800.
Lund und Stockholm
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