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Spatiotemporal variability of wave climate in the Gulf of Riga

Najafzadeh Fatemeh, Jankowski Mikolaj Z., Giudici Andrea, Männikus Rain, Suursaar Ülo, Viška Maija, Soomere Tarmo

Oceanologia

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2024

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Vol. 66 (1)

56--77

EN

Basic properties of wind wave climate in the Gulf of Riga, the Baltic Sea, are evaluated based on modelled wave fields, instrumentally measured and historical visually observed wave properties. Third-generation spectral wave model SWAN is applied to the entire Baltic Sea for 1990–2021 with a spatial resolution of 3 nautical miles (nmi, about 5.5 km) forced by the wind field of ERA5, to the Gulf of Riga and its entrance area with a resolution of 1 nmi (about 1.85 km), and to nearshore areas of this gulf with a resolution of 0.32 nmi (about 600 m). The calculations are performed for an idealised ice-free climate. Wave properties are represented by 36 directional and 32 frequency bins. The simulations are complemented by five sessions of instrumental measurements in the 2000s and two sets of historical visual wave observations from the island of Ruhnu and the Sõrve Peninsula for 1954–2011. Predominantly representing fetch-limited windseas, the wave climate in the gulf is milder and more intermittent than in the open Baltic Sea. The average significant wave height is mostly in the range of 0.6–0.8 m and peaks at 0.82 m inside the gulf. Typical wave periods are shorter than in the Baltic proper. The spatial pattern of wave heights, with higher wave intensity in the northern and eastern parts of the basin, follows anisotropy in wind conditions. Interannual variations are highly synchronised in different parts of the gulf. Their magnitude is less than 10% of the long-term average wave height. No long-term trend has been found in significant wave height and no distinct decadal variation exists inside the gulf.

2

Extreme wind waves in the Black Sea

Divinsky Boris V., Fomin Vladimir V., Kosyan Ruben D., Ratner Yuri D.

Oceanologia

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2020

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No. 62 (1)

23--30

EN

Results of the analysis of a long-term data set, including fields of significant wave heights of the surface wave components, and mixed (total) wave field in the Black Sea are presented. The data set was collected on the basis of retrospective calculations using the MIKE 21 SW spectral wave model with the atmospheric forcing based on the ERA-Interim data in the period from 1979 to 2017. A criterion is used to isolate the swell waves from the initial wave data set that takes into account the wave age. We used the experimental data to develop a regression relationship showing that the maximum possible wave height can exceed the significant wave height approximately one and a half times. Analysis of the spatial distribution of wave heights in the Black Sea suggests that a possibility exists that significant wave height of storm waves can be as high as ∼12 m. This result indicates that the actual heights of maximum waves in the Black Sea can reach 18-19 m. Three regions are distinguished on the basis of the wave potential. The times of manifestation of extreme situations in these regions are different: in the southwestern part of the sea, extreme storm situations occur, as a rule, in December-January; in the region south of the Crimea Peninsula this happens in February; in the northeastern part of the sea they occur in November. It was also found that the south-southeastern and eastern parts of the sea are most affected by swell.

3

Spatial variability of long-term trends in significant wave height over the Gulf of Gdańsk using System Identification techniques

Badur J., Cieślikiewicz W.

Oceanological and Hydrobiological Studies

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2018

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Vol. 47, No. 2

190--201

EN

The significant wave height field over the Gulf of Gdańsk in the Baltic Sea is simulated back to the late 19th century using selected data-driven System Identification techniques (Takagi-Sugeno-Kang neuro-fuzzy system and non-linear optimization methods) and the NOAA/OAR/ESRL PSD Reanalysis 2 wind fields. Spatial variability of trends in the simulated dataset is briefly presented to show a cumulative “storminess” increase in the open, eastern part of the Gulf of Gdańsk and a decrease in the sheltered, western part of the Gulf.

4

Wind wave climate of west Spitsbergen : seasonal variability and extreme events

Wojtysiak K., Herman A., Moskalik M.

Oceanologia

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2018

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No. 60 (3)

331--343

EN

Waves are the key phenomenon directly influencing coastal morphodynamics. Facing insufficient observations, wind wave climate of the west coast of Spitsbergen can be characterized on the basis of the modelled data. Here we have used the results of spectral wave models: Wave Watch III (WW3) hindcast and WAM in ERA-interim (ERAi) reanalysis. We have observed the presence of seasonal cycle with difference of up to 1 m between significant wave heights in summer and winter. In wave-direction analysis we have noticed the southwestern swell component of remarkably narrow width, thus we expect unidirectional swell impact on the coastline. Extreme events analysis revealed that storms occur mainly in winter, but the most energetic ones (significant wave height of up to 9.5 m) occur in spring and autumn. We have identified positive trends in storms’ frequency (2 storms per decade) and storms’ total duration (4 days per decade) on the south of the study area. More storms can result in the increase of erosion rate on the south-western coasts of Spitsbergen, but this change may be highly dependent on the sea ice characteristics. Wave heights of wind sea and swell are correlated with the relevant atmospheric circulation indices, especially the North Atlantic Oscillation. In the recent decade, the correlation is stronger with WW3 than with ERAi data, at some locations explaining over 50% (over 30%) of the total variance of wind sea (swell) wave heights. In ERAi data, the relationship with circulation indices seems sensitive to the length of the analysis period.

5

Parameters of wind seas and swell in the Black Sea based on numerical modeling

Divinsky B., Kosyan R.

Oceanologia

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2018

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No. 60 (3)

277--287

EN

The main objective of our work is to estimate the climatic peculiarities of the distribution of wind sea and swell in the Black Sea. The method of our research is numerical modeling. We tuned the spectral wave model DHI MIKE 21 SW for automatic separation of the components of surface waves. We estimated the peculiarities of the spatial distribution of the power of wind seas and swell in the basin of the Black Sea in the last 10 years (2007-2016). We determined the regions of domination of wind seas and swell in the field of mixed waves.

6

Assessment of wave climate and energy resources in the Baltic Sea nearshore (Lithuanian territorial water)

Jakimavičius D., Kriaučiūnienė J., Šarauskienė D.

Oceanologia

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2018

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No. 60 (2)

207--218

EN

The main task of the present research was to analyse wave climate and evaluate energy resources in the Lithuanian territorial waters of the Baltic Sea. Wave and wind parameters were analysed according to long-term measurement site data. Distribution of wave parameters in the Baltic Sea Lithuanian nearshore was evaluated according to wave modelling results. Wave energy resources were estimated for three design years (high, median and low wave intensity). The results indicated that in the coastal area of Lithuania, waves approaching from western directions prevail with mean wave height of 0.9 m. These waves are the highest and have the greatest energy potential. The strongest winds and the highest waves are characteristic for the winter and autumn seasons. In the Baltic Sea Lithuanian nearshore, the mean wave height ranges from 0.68 to 0.98 m, while the estimated mean energy flux reaches from 0.69 to 1.90 kW m−1 during a year of different wave intensity. Distribution of energy fluxes was analysed at different isobaths in the nearshore. Moving away from the coast, both wave height and wave power flux increases significantly when water depth increases from 5 to 20 m. Values of the mentioned parameters tend to change only slightly when the sea is deeper than 20 m. In a year of median wave intensity, the mean wave energy flux changes from 1.10 kW m−1 at 10 m isobaths to 1.38 kW m−1 at 30 m isobaths. The identified differences of wave height and energy along the selected isobaths are insignificant.

7

Depth of closure in the multi-bar non-tidal nearshore zone of the Baltic Sea: Lubiatowo (Poland) case study

Cerkowniak G. R., Ostrowski R., Stella M.

Biuletyn Instytutu Morskiego w Gdańsku

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2015

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Vol. 30, No. 1

180--188

EN

The paper deals with the natural sandy nearshore zone, located close to Lubiatowo in Poland (the south Baltic Sea). The study site is characterised by multi-bar sea bottom profile, intensively dissipating wave energy. The paper presents a verification of the depth of closure concept. The analysis and theoretical considerations are based on field data collected at the IBW PAN Coastal Research Station in Lubiatowo. The data comprises cross-shore bathymetric profiles and the deep-water wave buoy records. The depth of closure determined from bathymetric surveys was found to be bigger than the one calculated using parameters of the effective significant wave height.

PL

Artykuł dotyczy naturalnej piaszczystej strefy przybrzeżnej znajdującej się w pobliżu Lubiatowa w Polsce (południowy Bałtyk). Miejsce badań charakteryzuje się wielorewowym Profilem dna morskiego, powodującymi intensywną dyssypację energii fal. Praca przedstawia weryfikację koncepcji głębokości zamknięcia. Analiza i rozważania teoretyczne opierają się na danych terenowych zebranych w Morskim Laboratorium Brzegowym IBW PAN w Lubiatowie. Dane te zawierają profile batymetryczne poprzeczne do brzegu oraz rejestracje z głębokowodnej boi falowej. Głębokość zamknięcia wyznaczona z pomiarów batymetrycznych okazuje się większa niż obliczona z parametrów efektywnej fali znacznej.

8

Spatial patterns of the wave climate in the Baltic Proper and the Gulf of Finland

Soomere T., Räämet A.

Oceanologia

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2011

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No. 53 (1-TI)

335-371

EN

We make an attempt to consolidate results from a number of recent studies into spatial patterns of temporal variations in Baltic Sea wave properties. The analysis is based on historically measured and visually observed wave data, which are compared with the results of numerical hindcasts using both simple fetch-based one-point models and contemporary spectral wave models forced with different wind data sets. The focus is on the eastern regions of the Baltic Sea and the Gulf of Finland for which long-term wave data sets are available. We demonstrate that a large part of the mismatches between long-term changes to wave properties at selected sites can be explained by the rich spatial patterns in changes to the Baltic Sea wave fields that are not resolved by the existing wave observation network. The spatial scales of such patterns in the open sea vary from > 500 km for short-term interannual variations down to about 100 km for long-term changes.

9

Trends and extremes of wave fields in the north-eastern part of the Baltic Proper

Broman B., Hammarklint T., Rannat K., Soomere T., Valdmann A.

Oceanologia

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2006

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No. 48 (S)

165-184

EN

The paper analyses one of the longest contemporary wave measurements in the northern Baltic Sea, performed at Almagrundet 1978-2003. This record contains the roughest instrumentally measured wave conditions (significant wave height = c. 7.8 m) in the northern Baltic Proper until December 2004. The data for the years 1979-95, the period for which the data are the most reliable, show a linear rising trend of 1.8% per annum in the average wave height. The seasonal variation in wave activity follows the variation in wind speed. The monthly mean significant wave height varies from 0.5 m in May-July to 1.3-1.4 m in December-January. No corrections have been made in the analysis to compensate for missing values, for their uneven distribution, or for ice cover.