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Activities at GKSS related to D&A problems

This overview highlights the activities at the GKSS Research Centre related to wind over sea, including forced simulations, changes in storminess, and wave energy detection. It also explores dynamical downscaling and the impact of anthropogenic climate change on wave conditions in the North Sea.

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Activities at GKSS related to D&A problems

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  1. Activities at GKSS related to D&A problems Hans von StorchInstitute for Coastal ResearchGKSS Research CentreGeesthacht, Germany INTERESTED IN WIND OVER SEA

  2. Overview • Millennial forced runs "Erik the Red" and "Christof Columbus" • 1958-2000 regional downscaling/reconstruction • Changes storminess / WASA • Ocean waves and detection for (erosion relevant) wave energy change.

  3. Forced Simulation 1550-2000 simulation Changing solar forcing and time variable volcanic aerosol load; greenhouse gases

  4. Institut für Küstenforschung I f K Climate model used Atmosphere: ECHAM4 horizontal resolution T30 ~ 300 km at mid latitudes Ocean: HOPE-G horizontal resolution T42 ~ 200 km at mid latitudes increased resolution in the tropics Model provided as community climate by Model & Data Group at MPI for Meteorologyand run at German Climate Computing Centre (DKRZ)and computing facilities at FZ Jülich

  5. Control 1990 equilibrium Erik the Red Christoph Columbus More actual data via internet

  6. Information provided by Fidel González-Rouco andSimon Tett ECHO-G HadCM3 differences relative to the 1550-1800 average and are a 25-year running average.

  7. Institut für Küstenforschung I f K control forced

  8. 1958-2000 regional downscaling/reconstruction • Spectral nudging • Dutch coast extremes (maps) • K13 extremes wind & waves (return values)

  9. Institut für Küstenforschung I f K Concept of Dynamical Downscaling RCM Physiographic detail 3-d vector of state Known large scale state projection of full state on large-scale scale Large-scale (spectral) nudging

  10. Institut für Küstenforschung I f K Skill in representing marine winds significant wave height [days] wave direction [days] Red: buoy,yellow: radar, blue: wave model run with REMO winds

  11. Extreme wind speeds Southern North Sea Feser, pers. comm. DWD REMO 20-year return values of wind speed, based on daily 1992-97 data (color codes) plus from station data in NL (numbers in black)

  12. Institut für Küstenforschung I f K Skill in representing marine winds Extreme value analysis of significant wave height at platform K13 (southern North Sea) 2 5 10 25 years [m] 2 5 10 25 years [m] observed simulated Weisse, pers. comm. January 1980-January 1997

  13. Changing storminess / WASA • Geostrophic wind + pressure tendencies • Ekofisk • SMHI scenario

  14. Trends in storminess intra-annual 99% quantiles of geostrophic wind, averaged over many triangles. North Sea Baltic Sea Alexandersson, SMHI, 2003

  15. Bärring, 2003

  16. Weisse, pers. comm. 99% 95% 90% 50% 99% 95% 90% 50% Significant wave height Wind speed red: local observationssolid: RCM reconstruction (downscaling NCEP) + WAMdashed: WASA estimate + WAM

  17. Scenario for changed wind conditions in the wider North Sea area, end of 21st century (A2) Mean wind speed Storm wind speeds m/sec Rossby Center, Norrköping, Sweden

  18. Anthropogenic climate change shown by localwave conditions in the North Sea(Arnt Pfizenmayer, Hans von Storch) ABSTRACT: In the central North Sea we have observed an increase in the frequency of eastwardly propagating waves in the last 4 decades. To assess the significance of this change, wave statistics for the 20th century were reconstructed with a statistical model. With a linear multivariate technique (redundancy analysis), monthly mean air pressure fields over the North Atlantic and Western Europe were downscaled on the intramonthly frequency of directional wave propagation. When compared against this reference, the recent change appears statistically significant at the 5% level. In order to investigate the reason for this local climatic change, the reconstruction was compared with the downscaled results of control and transient GCM scenarios (ECHAM4-OPYC3) and with the results obtained in a high-resolution time-slice experiment with increased concentrations of greenhouse gases and aerosols. Both estimates are qualitatively consistent with the changes observed in the last 4 decades. We suggest that the recent increase in eastward propagation is a local manifestation of anthropogenic global climate change.

  19. Pfizenmayer and von Storch, 2002 Comparison of the 30 yr running mean of the monthly frequency of eastwardly propagating waves (3 h time steps, anomalies). The reconstruction of the 20th century (black line), the transient T42 run (dotted line), the T42 control run (grey line) and the time-slice experiment T106 (star) are shown. Dashed lines are the estimated 5, 95 and 99% confidence intervals.

  20. Pfizenmayer, 2002

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