Regional storm climate and related marine hazards in the NE Atlantic Hans von Storch und viele Kollegen Institute for Coastal Research, GKSS, Germany

How to determine decadal and longer variations in the storm climate? How has the NE Atlantic storm climate developed in the last few decades and last few centuries? How is the extratropical storm climate variability linked to hemispheric temperature variations? 4. How did wind-impact on storm surges and ocean waves develop in the past decades, and what may happen in the expected course of anthropogenic climate change?

How to determine decadal and longer variations in the storm climate? How has the NE Atlantic storm climate developed in the last few decades and last few centuries? How is the extratropical storm climate variability linked to hemispheric temperature variations? 4. How did wind-impact on storm surges and ocean waves develop in the past decades?

Changes of the wind climate Climate = statistics of weather, as given by distributions or parameters thereof, such as means, percentiles etc. Changes of wind stats difficult to determine, because of changing observation practices and environments. Almost all long record of wind observations are inhomogeneous, i.e., they do not only reflect changes of the wind statistics but also other factors, such as observation method, practice, location, analysis method ….

10-yearly sum of events with winds stronger than 7 Bft in Hamburg

Pressure based proxies Pressure readings are usually homogenous Annual percentiles of geostrophic wind (e.g., 95 or 99%iles) 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

How to determine decadal and longer variations in the storm climate? How has the NE Atlantic storm climate developed in the last few decades and last few centuries? How is extratropical storm climate variability linked to hemispheric temperature variations? 4. How did wind-impact on storm surges and ocean waves develop in the past decades?

Stockholm 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 (GRL)

How to determine decadal and longer variations in the storm climate? How has the NE Atlantic storm climate developed in the last few decades and last few centuries? How is the extratropical storm climate variability linked to hemispheric temperature variations? 4. How did wind-impact on storm surges and ocean waves develop in the past decades?

“Forced” simulation, 1000-2000 Simulation with climate model exposed to estimated volcanic, solar and GHG forcing. Number of strong wind events per season (wind at 10 m;  8 Bft, gales; every 12 hours) were counted.

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

How to determine decadal and longer variations in the storm climate? How has the NE Atlantic storm climate developed in the last few decades and last few centuries? How is the extratropical storm climate variability linked to hemispheric temperature variations? 4. How did wind-impact on storm surges and ocean waves develop in the past decades?

Aber wie sieht es regional und lokal aus? Hydrodynamisches Modell der Nordseezirkulation Katja Woth Globales Geschehen Dynamisches Downscaling Pegel St. Pauli Empirisches Downscaling Zusammenarbeit u. a. mit BAW, BSH, ALR Husum, FSK Norderney, Hamburg Port Authority u.a.

Stormcount 1958-2001 Change of # Bft 8/year t ≤ T t ≥ T Linearer Trend Stuerme in Anzahl/Jahr ermittelt fuer den Zeitraum 1958-2001.  alle Stuerme >= Bft 8 (17.2m/s)   Relativer Trend, d.h. Aenderungen relativ zum langjaehrigen Mittelwert. beachte, dass der bei schweren Stuermen oft nur 1-3 betraegt. Signifikanz wurde mit Hilfe Mann-Kendall Test getestet. Da wo die Nullhypothese "kein Trend" mit 5% Irrtumswahrsch. verworfen werden muss wurde das 95% Konfidenzintervall "D" fuer den Trend "x" geplottet (x-D <= x <= x+ D) Weisse et al., J. Climate, 2005

A2 - CTL: changes in 99 % - iles of wind speed (6 hourly, DJF): west wind sector selected (247.5 to 292.5 deg) HIRHAM RCAO Scenarios for 2085 Woth et al., 2005

How to determine decadal and longer variations in the storm climate How to determine decadal and longer variations in the storm climate? Use homogenous proxies for storminess. How has the NE Atlantic storm climate developed in the last few decades and last few centuries? An intensification in 1960-1990; thereafter activity has ceased somewhat. No significant changes since 1800. How is the extratropical storm climate variability linked to hemispheric temperature variations? Model simulation indicate that there is no obvious link during historical times, but that parallel signals a probable in the course of emerging anthropogenic climate change. How did wind-impact on storm surges and ocean waves develop in the past decades? Storm surges as well as ocean wave extremes develop mostly parallel to wind conditions; no significant increases in the past, except for an ongoing increase in the Southern North Sea.