scholarly journals Future Changes in Wave Conditions at the German Baltic Sea Coast Based on a Hybrid Approach Using an Ensemble of Regional Climate Change Projections

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 167
Author(s):  
Norman Dreier ◽  
Edgar Nehlsen ◽  
Peter Fröhle ◽  
Diana Rechid ◽  
Laurens M. Bouwer ◽  
...  
Keyword(s):  
21St Century ◽  
Wind Wave ◽  
Regional Climate ◽  
Hybrid Approach ◽  
Wave Modelling ◽  
Long Term Changes ◽  
Mean Wave Period ◽  
Wave Conditions ◽  
Sea Coast

In this study, the projected future long-term changes of the local wave conditions at the German Baltic Sea coast over the course of the 21st century are analyzed and assessed with special focus on model agreement, statistical significance and ranges/spread of the results. An ensemble of new regional climate model (RCM) simulations with the RCM REMO for three RCP forcing scenarios was used as input data. The outstanding feature of the simulations is that the data are available with a high horizontal resolution and at hourly timesteps which is a high temporal resolution and beneficial for the wind–wave modelling. A new data interface between RCM output data and wind–wave modelling has been developed. Suitable spatial aggregation methods of the RCM wind data have been tested and used to generate input for the calculation of waves at quasi deep-water conditions and at a mean water level with a hybrid approach that enables the fast compilation of future long-term time series of significant wave height, mean wave period and direction for an ensemble of RCM data. Changes of the average wind and wave conditions have been found, with a majority of the changes occurring for the RCP8.5 forcing scenario and at the end of the 21st century. At westerly wind-exposed locations mainly increasing values of the wind speed, significant wave height and mean wave period have been noted. In contrast, at easterly wind-exposed locations, decreasing values are predominant. Regarding the changes of the mean wind and wave directions, westerly directions becoming more frequent. Additional research is needed regarding the long-term changes of extreme wave events, e.g., the choice of a best-fit extreme value distribution function and the spatial aggregation method of the wind data.

scholarly journals Long-term changes of river discharge regime in Latvia

2008 ◽  
Vol 39 (2) ◽  
pp. 133-141 ◽  
Author(s):  
Maris Klavins ◽  
Valery Rodinov
Keyword(s):  
Climate Variability ◽  
River Discharge ◽  
Water Resource Management ◽  
Regional Climate ◽  
Hydrological Regime ◽  
High Water ◽  
Regime Changes ◽  
Long Term Changes ◽  
Discharge Regime

The study of changes in river discharge is important for regional climate variability characterization and for development of an efficient water resource management system. The hydrological regime of rivers and their long-term changes in Latvia were investigated. Four major types of river hydrological regimes, which depend on climatic and physicogeographic factors, were characterized. These factors are linked to the changes observed in river discharge. Periodic oscillations of discharge, and low- and high-water flow years are common for the major rivers in Latvia. A main frequency of river discharge regime changes of about 20 and 13 years was estimated for the studied rivers. A significant impact of climate variability on the river discharge regime has been found.

Numerical Prototyping of Floating Offshore Wind Turbines: Virtual Operation in Real Environmental Conditions

2020 ◽  
Author(s):  
Daniel Milano ◽  
Christophe Peyrard ◽  
Matteo Capaldo
Keyword(s):  
Wind Turbines ◽  
Wind Wave ◽  
Fatigue Analysis ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Direction ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Wave Conditions

Abstract The numerical fatigue analysis of floating offshore wind turbines (FOWTs) must account for the environmental loading over a typical design life of 25 years, and the stochastic nature of wind and waves is represented by design load cases (DLCs). In this statistical approach, combinations of wind speeds and directions are associated with different sea states, commonly defined via simplified wave spectra (Pierson-Moskowitz, JONSWAP), and their probability of occurrence is identified based on past observations. However, little is known about the difference between discretizing the wind/wave direction bins into (e.g.) 10deg bins rather than 30deg bins, and the impact it has on FOWT analyses. In addition, there is an interest in identifying the parameters that best represent real sea states (significant wave height, peak period) and wind fields (profile, turbulence) in lumped load cases. In this context, the aim of this work is to better understand the uncertainties associated to wind/wave direction bin size and to the use of metocean parameters as opposed to real wind and sea state conditions. A computational model was developed in order to couple offshore wind turbine models with realistic numerical metocean models, referred to as numerical prototype due to the highly realistic wind/wave conditions in which it operates. This method allows the virtual installation of FOWTs anywhere within a considered spatial domain (e.g. the Mediterranean Sea or the North Sea) and their behaviour to be evaluated in measured wind and modelled wave conditions. The work presented in this paper compares the long-term dynamic behaviour of a tension-leg platform (TLP) FOWT design subject to the numerical prototype and to lumped load cases with different direction bin sizes. Different approaches to representing the wind filed are also investigated, and the modelling choices that have the greatest impact on the fidelity of lumped load cases are identified. The fatigue analysis suggests that 30deg direction bins are sufficient to reliably represent long-term wind/wave conditions, while the use of a constant surface roughness length (as suggested by the IEC standards) seems to significantly overestimate the cumulated damage on the tower of the FOWT.

Long-term Changes of Waves at the German Baltic Sea Coast: Are There Trends from the Past?

2020 ◽  
Vol 95 (sp1) ◽  
pp. 1416
Author(s):  
Norman Dreier ◽  
Rain Männikus ◽  
Peter Fröhle
Keyword(s):  
Baltic Sea ◽  
The Past ◽  
Long Term Changes ◽  
Sea Coast

scholarly journals WIND WAVE FREQUENCIES IN A TROPICAL CYCLONE REGION

1978 ◽  
Vol 1 (16) ◽  
pp. 3
Author(s):  
Rodney J. Sobay
Keyword(s):  
Tropical Cyclone ◽  
Continental Shelf ◽  
Wind Wave ◽  
Wave Climate ◽  
Extreme Value Analysis ◽  
Local Wind ◽  
Value Analysis ◽  
Coral Sea ◽  
Wave Conditions

Australia's Coral Sea coast from Bundaberg north to Cape York has a wind wave climate that is almost unique. The coastline is afforded unparalleled protection from the 1900 km Great Barrier Reef, yet it lies in a tropical cyclone region and must expect recurrent intense wind and wave conditions. The Great Barrier Reef is a continuous chain of quite separate coral reef clusters located near the edge of the continental shelf. The separate reefs are often exposed at low tide, the inner fringe of the clusters ranges from 10 km offshore north of Cairns to 200 km offshore south of Rockhampton and the outer fringe is typically some 50 km further offshore, beyond which the ocean bed drops rapidly away. Incident wave energy from the Coral Sea is invariably dissipated on the outer edge of the Reef and wave conditions on the continental shelf can reasonably be considered due to local wind conditions. The Reef imposes an effective fetch limitations on wave generation over the continental shelf and there is, as a consequence, a moderately rapid response of wave conditions to changes in local wind conditions. A pronounced diurnal variation in the wind climate is reflected also in the wave climate and the stability of the region's tropical climate leads to frequent calm to slight sea conditions. This stability however is occasionally exploded by the generation and passage of a tropical cyclone in mid to late summer. Large waves can be generated by the intense winds of the tropical cyclone (hurricane or typhoon), often an order of magnitude greater than those in response to non-cyclonic events. The rational design of coastal structures and the rational pursuit of coastal zone management requires appropriate estimates of the frequency of occurrence of waves of various heights. Ideally such information is obtained from an extreme value analysis of long term wave records at the particular site in question. Permanent wave recording programs unfortunately have only become common practice in the present decade and wave records, if they exist at all for a particular site, are rarely long enough to allow a satisfactory extreme value analysis. It is clear, in the Australian context at least, that historical wave data alone is not yet sufficient to derive satisfactory estimates of long term wave frequencies. The alternative is system modelling. Wind is a major meteorological variable and its long term recording has been a standard meteorological practice now for over half a century.

scholarly journals LONG-TERM CHANGES IN THE PRESIPITATION AT THE BLACK SEA COAST OF THE CAUCASUS

2020 ◽  
Vol 1 (5) ◽  
pp. 161-167
Author(s):  
A.V. Parfenova ◽  
◽  
L.V. Dashkevich ◽  
Keyword(s):  
Black Sea ◽  
Coefficient Of Variation ◽  
Meteorological Station ◽  
The Black Sea ◽  
The Caucasus ◽  
Modern Period ◽  
Black Sea Coast ◽  
Long Term Changes ◽  
Sea Coast

Long-term changes in the amount of precipitation on the Black Sea coast of the Caucasus according to data of the hydro-meteorological stations Anapa, Tuapse and Sochi are considered. The observation data analysis of for the selected periods revealed an increase in the average yearly precipitation from the beginning of the twentieth to the beginning of the twenty-first centuries for all hydro-meteorological stations with a slight decrease in the coefficient of variation. Seasonal changes in precipitation regime are pronounced in the region. The highest increase in seasonal precipitation was noted at the Anapa hydro-meteorological station for winter, then for spring and autumn. At the Tuapse and Sochi hydro-meteorological stations also tended to increase precipitation in spring and autumn, but was noted a slight decrease in winter in the modern period. At the same time, for all seasons such growth is provided mainly by an increase in the minimum seasonal values (for all stations), as well as maximum ones in spring (for all stations) and autumn (hydro-meteorological station Anapa). In modern period relative to the twentieth century it is possible to note a slight decrease in the coefficient of variation in winter and spring (for all hydro-meteorological stations), and an increase in summer (for hydro-meteorological stations Anapa and Tuapse). The redistribution of precipitation by seasons was revealed from the beginning of the twentieth to the beginning of the twentyfirst centuries. The most significant changes affected the hydro-meteorological station Tuapse: the share of autumn and spring precipitation increased from 25 to 31 % and from 18 to 22 %, respectively, while the share of summer precipitation decreased from 26 to 18 %. The share of winter precipitation increased from the first to the third selected periods (from 30 to 35 %), after which it decreased to 29 % in the modern period.

scholarly journals Long-term changes in the heat–mortality relationship according to heterogeneous regional climate: a time-series study in South Korea

BMJ Open ◽  
2016 ◽  
Vol 6 (8) ◽  
pp. e011786 ◽  
Author(s):  
Seulkee Heo ◽  
Eunil Lee ◽  
Bo Yeon Kwon ◽  
Suji Lee ◽  
Kyung Hee Jo ◽  
...  
Keyword(s):  
Time Series ◽  
South Korea ◽  
Regional Climate ◽  
Time Series Study ◽  
Long Term Changes ◽  
Series Study

scholarly journals Investigation of Forest Area Change in the 19th–21st Century Using Military Topographic Maps

2020 ◽  
Author(s):  
Rūta Puzienė ◽  
Asta Anikėnienė
Keyword(s):  
21St Century ◽  
Statistical Data ◽  
Topographic Maps ◽  
Forest Land ◽  
Land Area ◽  
Current Increase ◽  
Long Term Changes ◽  
Forest Area Change ◽  
Forest Coverage

Long-term changes of the Earth’s cover are imperceptible. Several generations change, people do not see what had been there before they were born, they do not see what happens after they are gone, meanwhile, maps preserve the image of the surroundings that was prevailing hundreds of years ago and the analysis of which allows highlighting certain occurring tendencies. The present study aims at the analysing the change in the forest coverage on the territory of Lithuania employing statistical data and analysing the change in the forest land area from the 19th c. until the 21st c. in the Elektrenai municipality using military topographic maps. During the study, digitalised archival maps and devectorised forest areas were used, and the obtained results were compared. The information provided in the maps reveals a decrease in the forest land area during during 19th–20th c. and an increase during the 20th–21st c., however, the current increase has not compensated the earlier decrease.

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