4 results
Filters
Settings
Now showing1 - 4 of 4
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Long-term Changes of Waves at the German Baltic Sea Coast: Are There Trends from the Past?(2020-03); ; Long-term changes of waves at the German Baltic Sea Coast: Are there trends from the past? In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020.JournalofCoastalResearch,SpecialIssueNo.95,pp.1416-1421.CoconutCreek(Florida),ISSN0749-0208. For the development of future coastal and flood protection strategies and methods as well as the adaptation of today's existing protection structures, possible impacts of climate change on the long-term changes of the local wave conditions in the future and the past need to be analysed and assessed. In this study, two main research questions are raised: (i) Are there any long-term changes of the waves derived from numerical model data?, (ii) How well can the COSMO model reproduce the wave climate for the past? To answer those questions, two reanalysis wind data sets (COSMO-REA6 and coastDat2) for the past based on the COSMO model are used for the calculation of long-term time series of hourly wave parameters (SWAN) at the German Baltic Sea Coast. The long-term changes of the average wave conditions in the past are analysed and assessed for the coastDat2 data set for both average values and the frequency of occurrence of significant wave height and mean wave direction over time periods of 30 years. Moreover, the statistical significance of the changes of the frequency is assessed based on statistical hypothesis tests. In agreement with previous analysis of the future long-term changes of the wave climate, a large multi-(decadal), spatial and seasonal variability of the changes exist and the changes depend on the exposition of the coast towards the prevailing westerly winds. At westerly wind exposed locations, trends towards an increase of the 30 year annual averages of significant wave height up to 5 % were found, with possible larger changes of the 30 year seasonal averages, and trends towards more waves coming from westerly directions. The long-term changes of extreme wave conditions in the past are analysed based on extreme value statistics and over time periods of 30 years. Slightly increasing respectively decreasing trends between -5 % and +9 % (-0.16 m/+0.27 m) of significant wave heights with a return period of 200 years have been found at westerly respectively easterly wind exposed locations.Publicationtype: Journal Article104 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Operational wave forecast in the German Bight as part of a sensor- and risk based early warning systemToday's available flood- respectively storm surge warning systems for the German North Sea coast consist exclusively of water level forecasts. Other hydrodynamic loads caused by wind waves and local currents as well as the resistance of the flood protection structure itself (e.g. coastal dikes, flood protection walls etc.) are not taken into account. Therefore, an operational now- and forecast system for waves and wave induced hydrodynamic loads is set up that consists of available field measurements and data from numerical wave simulations in the German Bight. A hybrid model approach is used for the forecast of hydrodynamic loads on sea dikes. The approach combines numerical results from the phase integrated spectral wave forecast model (SWAN) and an empirical wave run-up approach (EurOtop) for the now- and forecast of average wave run-up heights at a sea dike on the North Frisian Island of Pellworm. The operational system is demonstrated exemplarily for the forecast of a severe storm event on the 5-6th December 2013 (German name "XAVER"). The qualitiy of the forecast is assessed seperately for the local nearshore wave conditions as well as the average wave run-up heights on the basis of available field measurements.Publicationtype: Conference Paper176 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the long-term changes of extreme wave heights at the German Baltic Sea Coast(2016-03-01); ; ; ; The assessment of extreme wave heights is of great importance for the design of coastal protection strucutres. This paper aims to present long-term changes of extreme wave heights at several selected locations at the German Baltic Sea Coast. Annual maximum significant wave heights were selected from the hourly wave data obtained from a hybrid approach (wind-wave-correlations combined with numerical simulations on the basis of the SWAN model) for a total period of 140 years, spanning from 1961 to 2100. The future projections of wind data were dreived from the regional COSMO-Climate Local Model for two emission scenarios A1B and B1. The extreme wave heights at each location were estimated from the respective best-fitting distribution, log-normal or Weibull distribution. The results indicate that, the long-term changes of extreme wave heights are related to the emission scenarios used in the regional climate model, the distribution chosen for the estimating (up to +9.6%) and also the sample size for the extreme value analysis (up to +8.7%). These factors should be carefully considered in the future coastal structure design.Publicationtype: Journal Article122 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Changes of 21st Century's average and extreme wave conditions at the German Baltic Sea Coast due to global climate changeOn the basis of hourly simulated wind data from a regional circulation model (Cosmo-CLM) long-term time series (1960-2100) of wave parameters were compiled for two of the SRES scenarios A1B, B1 at three locations along the German Baltic Sea Coast. The time series of wave parameters were calculated with the help of statistical correlations between observed wind and wave data, which were derived for the three locations in the study area. Furthermore, we applied a wave model for the Western Baltic Sea to correct some of the calculated wave information. The key findings of this study are that: (i) significant changes of average wind conditions can directly be linked to significant changes of the average wave conditions, (ii) a spatial pattern for the changes of average wave conditions can be found, (iii) no general trend can be found for the changes of extreme wave conditions. Comparisons of wind conditions, as simulated by the regional circulation model, for the past and the future are showing two main changes: (a) increases of average wind velocities to the end of the 21 st century up to +4% and (b) more wind events from westerly and less events from easterly directions. The changes of the average wind velocities are resulting in increases of the average significant wave heights at westerly wind exposed locations up to +7% and small decreases of the average significant wave heights at easterly wind exposed locations. The future changes of the wave directions, with more wave events from W-NW and fewer events from N-NE, can be connected to the future changes of wind directions. Analyses of extreme wave heights with a return period of 200 years are showing both increasing and decreasing changes of up/down to +/-14%. At one location of the study area (Warnemünde) a slight increasing trend for the change of extreme wave heights to the end of the 21st century exists. © Coastal Education & Research Foundation 2013.Publicationtype: Journal Article221