Wyniki wyszukiwania - BazTech

1

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

|

2024

|

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

Numerical simulations of wave climate in the Baltic Sea: a review

Soomere Tarmo

Oceanologia

|

2023

|

Vol. 65 (1)

117--140

EN

Efforts towards the numerical simulation of the Baltic Sea wave properties, started in the 1950s, have reached maturity by the implementation of contemporary third generation spectral wave models, such as WAM and SWAN. The purpose of this paper is to give an overview of the relevant efforts since the beginning of numerical wave simulations. The Sverdrup-Munk-Bretschneider (SMB) type models are still valuable tools for rapid estimates of some properties of wave climate in single locations. The spatial resolution of spectral wave models for the entire sea has increased from about 20 km to 1 km, and to 100–200 m in specific areas. The number of directional bins has increased from 10–15 to 24–36 and the number of spectral frequency bins from about 15 to 35–42. The models replicate all main features of the wave climate of the Baltic Sea, such as an overall mild but intermittent wave climate, the predominance of short windseas and the scarcity of long swell, east-west asymmetry, the strong impact of seasonal ice, and the specific properties of wave growth in some areas. The wave climate changes involve variations in regional wave intensity, core properties of wave-driven sediment transport and wave set-up. Reconstruction of wave properties in the nearshore, archipelago areas, and in narrow subbasins remains a challenge. These areas require finer spatial resolution and possibly advancement of wave physics to account for changes in the spectral composition of wave fields and specific features of wave growth in narrow basins. Progress in these fields is a pillar for a number of applications, from the quantification of sediment transport to proper input into management issues of the coastal zone.

3

The impact of surface currents and sea level on the wave field evolution during St. Jude storm in the eastern Baltic Sea

Viitak M., Maljutenko I., Alari V., Suursaar Ü., Rikka S., Lagemaa P.

Oceanologia

|

2016

|

No. 58 (3)

176--186

EN

A third generation numerical wave model SWAN (Simulating WAves Nearshore) was applied to study the spatio-temporal effect of surface currents and sea level height on significant wave height; and to describe the mechanisms responsible for wave–current interaction in the eastern Baltic Sea. Simulation results were validated by comparison with in situ wave measurements in deep and shallow water, carried out using the directional wave buoy and RDCP respectively, and with TerraSAR-X imagery. A hindcast period from 23 to 31 October 2013 included both a period of calm to moderate weather conditions and a severe North-European windstorm called St. Jude. The prevailing wind directions were southerly to westerly. Four simulations with SWAN were made: a control run with dynamical forcing by wind only; and simulations with additional inputs of surface currents and sea level, both separately and combined. A clear effect of surface currents and sea level on the wave field evolution was found. It manifested itself as an increase or decrease of significant wave height of up to 20%. The strength of the interaction was influenced by the propagation directions of waves and surface currents and the severity of weather conditions. An increase in the wave height was mostly seen in shallower waters and in areas where waves and surface currents were propagating in opposite directions. In deeper parts of the eastern Baltic Sea and in case of waves and surface currents propagating in the same direction a decrease occurred.

4

Analizator Internetu semantycznego

Skulimowski M.

Studia Informatica

|

2011

|

Vol. 32, nr 2A

495-506

PL

W artykule przedstawiony jest system SWAN (Semantic Web Analyzer) wyszukujący w Internecie informacje zapisane w formatach RDF i OWL, stworzonych na potrzeby Internetu Semantycznego. Informacje znalezione przez system SWAN zapisywane są w relacyjnej bazie danych, co umożliwia ich dalsze przetwarzanie i wykorzystanie.

EN

In this article the SWAN system (Semantic Web Analyzer) is presented. This system is designed for searching the Web information stored in RDF and OWL formats developed for the Semantic Web. The data found by SWAN are stored in a relational database, allowing for their further processing and using.

5

Zastosowanie pomiarów ruchu i sygnalizacji do różnicowania usług transportowych w heterogenicznych sieciach IP integrujących sieci ad-hoc z sieciami z infrastrukturą

Natkaniec M., Gozdecki J., Pach A. R.

Pomiary Automatyka Kontrola

|

2007

|

R. 53, nr 3

46-51

PL

W opracowaniu przedstawiono architekturę QoS sieci, umożliwiającej zapewnienie żądanej jakości świadczenia usług transportowych w mieszanych sieciach ad-hoc - infrastruktura. Różnicowanie usług dla czterech klas ruchu osiągnięto dzięki rozszerzonemu protokołowi SWAN oraz różnicowaniu usług w warstwie 3. Opisano pomiary niezbędne do efektywnego różnicowania usług w sieciach WLAN. Przedstawiono również przykładowe wyniki pomiarów zrealizowanych za pomocą modułu pomiarowego warstwy MAC, potwierdzające poprawność różnicowania usług w takich sieciach. Opisano także metody zapewnienia QoS w sieci przewodowej pomiędzy komunikującymi się terminalami.

EN

The ad-hoc and infrastructure QoS network architecture that allows for required quality transport services provisioning is presented in this study. The services differentiation for four traffic classes is achieved through the extended SWAN protocol and layer 3 differentiation. The measurements indispensable for effective services differentiation in WLAN networks are described. The measurement examples from MAC layer measurement module that confirm the services differentiation correctness are presented. The methods for supporting QoS in fixed networks between terminals are also described.