68 research outputs found
Kinetic theory of Rossby waves : abstract of the investigations presented to obtain the academic degree of Doctor of mathematics
http://www.ester.ee/record=b2470665*es
Run-up characterstics of symmetrical solitary tsunami waves of unknown shapes
The problem of tsunami wave run-up on a beach is discussed in the framework
of the rigorous solutions of the nonlinear shallow-water theory. We present an
analysis of the run-up characteristics for various shapes of the incoming
symmetrical solitary tsunami waves. It will be demonstrated that the extreme
(maximal) wave characteristics on a beach (run-up and draw-down heights, run-up
and draw-down velocities and breaking parameter) are weakly dependent on the
shape of incident wave if the definition of the significant wave length
determined on the 2/3 level of the maximum height is used. The universal
analytical expressions for the extreme wave characteristics are derived for the
run-up of the solitary pulses. They can be directly applicable for tsunami
warning because in many case the shape of the incident tsunami wave is unknown.Comment: Submitted to PAGEOP
Modelling of wave climate and sediment transport patterns at a tideless embayed beach, Pirita Beach, Estonia
Nearshore sand transport patterns along the tideless, embayed Pirita beach, Tallinn, Estonia, have been investigated utilizing high-resolution modelling of wave processes combined with bathymetric surveys and sediment textural analyses of the nearshore sea floor. Textural analysis showed the mean grain size is about 0.12 mm. Fine sand (0.063–0.125 mm) accounts for about 77% of the sediments. Coarser-grained sand (0.28 mm) dominates along the waterline. Based upon the spatial distribution of the mean grain size and basic features of the local wave activity, properties of the Dean Equilibrium Beach Profile were determined.
Alongshore sediment transport was calculated based upon a long-term time series of wave properties along the beach, and the CERC formula applied to about 500 m long beach sectors. The time series of wave fields and the properties of the local wave climate were modelled using a triple nested WAM wave model with an extended spectral range for short waves. The model is forced by open sea wind data from Kalbådagrund for the years 1981–2002. Results indicate that typical closure depth at Pirita is 2.5 m. The width and mean slope of the equilibrium profile are 250 m and 1:100, respectively. Southward transport dominates in the northern sections of the beach whereas no prevailing transport direction exists in the southern sections. This pattern has several nontrivial implications for the planning of beach protection activities
Changes in wave dynamics at the south-eastern coast of the Baltic Proper during 1993–2008
Using data gathered by visual wave observations at three Lithuanian coastal observation sites during 1993-2008, we make an attempt to relate the recent changes in the intensity of coastal processes on the Lithuanian coast to changes in the local wave regime. There exist considerable interannual variations in the overall wave activity but no statistically significant trends in wave heights for the study period. The directional distribution of wave approach directions has become considerably narrower since about 2002. This feature is most prominent at Palanga where since 2002 almost all waves have approached from SW. This change apparently leads to a decrease in the sediment supply to the Curonian Spit and to a certain starvation of the Lithuanian coast
Impact of changes in sea ice cover on the wave climate of semi-enclosed, seasonally ice-covered water bodies at temperate latitudes: a case study in the Gulf of Riga
We analyse potential changes in the average and cumulative properties of wind waves owing to the loss of sea ice in regions that are currently seasonally ice-covered. The focus is on the Gulf of Riga, located in the eastern Baltic Sea at higher temperate latitudes. This water body is almost isolated from the rest of the Baltic Sea in terms of wave and ice fields. We compare the statistical properties of wave time series from a hypothetical ice-free wave simulation for the period 1990â2021 with truncated ones in which waves are ignored during the ice season. These simulations are made using the SWAN model with a spatial resolution of about 1 nautical mile for the whole gulf and down to 300 m in its nearshore, and forced with ERA5 wind data. The presence of seasonal ice cover insignificantly impacts the formal average wave properties, but the total loss of sea ice will significantly increase the levels of annual cumulative wave energy and its flux, and will thus add considerable energy to coastal processes in this water body
Spatial variations in the Caspian Sea wave climate in 2002-2013 from satellite altimetry
The core properties of the wave climate and its changes in the Caspian Sea
are established in terms of the annual mean significant wave height and its
regional changes in 2002-2013 based on the outcome of the satellite altimetry
mission JASON-1. Remotely estimated wave heights are validated against
properties of the empirical distribution of instrumentally measured wave
heights in the southern Caspian Sea and monthly averages of visually observed
wave heights at three locations. A correction for systematic differences leads
to very good correspondence between monthly averaged in situ and satellite data
with a typical root mean square difference of 0.06 m. The average significant
wave height in the Caspian Sea is 0.5-0.7 m in the northern basin of the sea,
around 1.2 m in large parts of the central and southern basins and reaches up
to 1.8 m in the northern segment of the central basin. The basin-wide average
wave intensity varied insignificantly in the range of 1.02-1.14 m in 2002-2013.
These estimates overestimate the wave heights by about 30% because low wave
conditions are ignored. Substantial and statistically significant changes in
the wave height occurred in certain areas. The wave height decreased by 0.019
+- 0.007 m/yr in the eastern segment of the central basin and by 0.04 +- 0.04
m/yr in the western segment of the southern basin. These changes can be
explained by an increase in the frequency of westerly winds at the expence of
southerly winds. Both basin-wide and regional extreme wave heights exhibit
large interannual variations but do not show any significant trend. The
patterns of changes in mean and extreme wave height are different. The average
wave height has increased while the extreme wave height has decreased in the
eastern segment of the southern basin.Comment: 16 pages, 10 figure
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