Page 1 Storminess in N Europe and E Canada Hans von Storch Institute for Coastal Research, GKSS...

Storminess in N Europe and E Canada

Hans von StorchInstitute for Coastal Research, GKSS Research Center, Germany

and KlimaCampus Hamburg, Germany

28-30 January 2008 - IDAG Spring Meeting, Boulder, Colorado

N Europe storminess

Relevant publicationsSchmidt, 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-yThe 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

Challenge Storminess best represented by wind statistics, possibly derived quantities such as stream function, vorticity, but wind time series are almost always• inhomogeneous• too shortNo robust link to level temperature, but to pattern of seasonally mean air pressure.

Example of inhomogeneities in wind records

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 inrecent 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.“

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

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.

N Europe

Geostropic wind stats N Europe

Relevant publications 99%iles of annual geostrophic wind speedsfor a series of station triangles in the North Sea regions and in the Baltic Sea region.

Alexandersson et al., 2002

Local pressure stats since 1800

Relevant publications

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.

StockholmLund

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

Geostrophic stats

21 year Gaussian filtered

normalized

24 hr pressure change stats

normalized

E Canada + Grønland

Matulla, C., and H. von Storch, 2008: Changes in Eastern Canadian Storminess since 1880. submitted

E Canadian stations available

more

less

Direct estimates

Subarctic

Arctic

Regressing seasonal mean SLP on

low pressure percentiles

Reconstructing pastlow pressure percentiles

Subarctic 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.

Reserve

Stormcount 1958-2001

Relevant publications

Wei

sse

et a

l., J.

Clim

ate,

200

5

Change of # Bft 8/year

t ≤ T t ≥ T

Warming and Storms in the N Atlantic

(11-yr running means)

NH Temp & NA storm count:No obvious correlation in simulated historical

times

Fisc

her-B

runs

et a

l., 2

005

Hamburg – Storm surges Inhomogeneity

Inhomogeneity

Regionale Entwicklung der Temperatur und Sturmtätigkeit

Lund und Stockholm

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.

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