1,720,980 research outputs found
The attenuation of waves under the action of rain
No full textThe well known but, until now, unquantified, damping effect of rainfall on water waves is established experimentally. Artificial rain of intensity up to 600 mm hr-1 consisting of raindrops with equivalent diameter 3.2 mm is allowed to fall onto mechanically generated progressive and standing waves in no-wind conditions. The amplitude of the progressive wave is measured before the wave enters the raining section and after it exits. From the amplitude ratio in raining and non-raining conditions the spatial damping due to rain is derived for the progressive waves on the assumption of exponential damping. The resonance curve and the damping of standing waves in raining and non-raining conditions is also studied. The damping due to rain can be described by an eddy viscosity υE. All the experiments seem consistent with a value of υE of 0.3 cm2sec-1. An estimation of the damping effect of the rain-introduced variable stresses on the water surface is also made. Their effect is calculated to be trivial. The damping of waves with rain can be explained if the wind speed decreases when it starts to rain. The correlation of wind speed with the onset of rain is investigated by the use of 1 min wind speed time series. It is found that for wind speeds greater than 20 knots (10 m sec-1) the wind speed increases with the start of rain. Some possible effects of the wave damping due to rain on wave-growth and wave breaking are discussed.</p
Coastal sea level trends in Southern Europe
No full textLow frequency sea level variability in the Mediterranean Sea and in the Atlantic Iberian coast is investigated by use of tide gauge records. The five tide gauge records that span most of the 20th century show positive trends between 1.2 and 1.5 ± 0.1 mm yr?1 and negative accelerations between ?0.3 ± 0.3 and ?1.5 ± 0.4 mm yr?1 century?1. Sea level trends obtained from the 21 longest records (>35 yr) are smaller in the Mediterranean (0.3 ± 0.4 to ?0.7 ± 0.3 mm yr?1) than in the neighbouring Atlantic sites (1.6 ± 0.5 to –1.9 ± 0.5 mm yr?1) for the period 1960–2000. Decadal sea level trends in the Mediterranean are not always consistent with global values, in particular for the 1990s, during which the Mediterranean has shown enhanced sea level rise of up to 5 mm yr?1 compared to the global average (mostly attributed to higher warming). The atmospheric and steric contributions to the observed sea level trends for 1960–2000 are also examined. The atmospherically induced sea level is obtained from a barotropic model forced by wind and atmospheric pressure. The atmospheric contribution accounts for 20–50 per cent of the observed yearly sea level variability and introduces negative trends of –0.2 to –0.9 mm yr?1. The steric sea level, obtained from T and S climatologies, has negative trends ranging from ?2.1 ± 0.6 to ?0.1 ± 0.3 mm yr?1. Other shorter tide gauge records (>7 yr) are used to quality check longer series and to explore their consistency with the long-term records and identify short but apparently consistent tide gauge records
Shipowner's limitation of liability
No full textAt present, three international conventions (one of which has been modified by many signatory states to produce a fourth regime), together with certain pre-existing national regimes, provide this entitlement to limit most types of private law liability arising in the ordinary course of the shipowner’s activities.Limitation may be invoked by the shipowner in two principal ways: by way of a defence, or by commencing a limitation action, which latter normally involves constituting a limitation fund. Whether the shipowner should take the initiative and start a limitation action, or whether he or she should wait and use limitation as a defence, will depend on the choice of fora available. Significant differences among jurisdictions inevitably give rise to forum-shopping.In the course of this book’s practical explanation and discussion of shipowners’ rights to limit their liability, the authors consider how the conflict of laws rules of various jurisdictions might be used by parties in international commerce to raise the most advantageous defence or select the most suitable tribunal to commence a limitation action. For each potentially applicable limitation regime, the book identifies the amount to which liability is limited and the tests that apply when a claimant wishes to challenge a shipowner’s right to limit liability.Among the issues brought to the fore are the following:-- right to the lowest limit versus the strongest protection of the right to limit;- circumstances under which the ship against which the action is brought may be arrested and sold;- when the shipowner’s right to limit can be challenged and denied;- action in rem for collisions;- freezing injunctions;- direct action against an insurer. The book also discusses various specific liability regimes that address damage suffered by passengers, damage to cargo interests, oil pollution damage from tankers, damage from bunker oil from non tankers, and damage caused by hazardous and noxious cargoes.As an in-depth exploration and analysis of the differences between the various limitation regimes that provide shipowners with a global entitlement to limit liability – and the broader legal issues such limitation rights gives rise to – this book will prove invaluable to any party involved in shipping disputes. Lawyers representing either shipowners (and other parties with an interest in the ship’s operations) or claimants will clearly identify the major issues related to the selection of the appropriate forum for the limitation of liability, including procedural details
Seasonal sea level cycle in the Caribbean Sea
No full textThe seasonal sea level cycle has been investigated in the Caribbean Sea using altimetry and tide gauge time series from 27 stations and is characterized by large spatial variability. The coastal annual harmonic has amplitudes that range from 2 cm to 9 cm, peaking between August and October and semi-annual harmonic with maximum amplitude of 6 cm, with most stations peaking in April and October. The coastal seasonal sea level cycle contributes significantly at most areas to sea level variability and can explain the sea level variance up to 78%. The barometric effect on the coastal sea level seasonal cycles is insignificant in the annual component but dominant at 9 stations in the semi-annual cycle. The seasonal sea level cycle from 18 years of altimetry confirm the results obtained from the tide-gauges and allow us to identify some dominant sea level forcing parameters in the annual and semi-annual frequencies such as the Panama-Colombia gyre driven by the wind stress curl and the Caribbean Low Level Jet modulating the sea level in the northern coast of South America and linked to the local upwelling. The seasonal sea level cycle in the Caribbean Sea is unsteady in time, with large variations in amplitude and phase lag at most of the stations, where the 5-year amplitude in the coastal annual cycle can change over 6 cm in a 24 year period. The seasonal sea level cycle peaks about October when the probability of coastal impacts increases, especially in the northern coast of South America where the range is larger
The forcing of mean sea level variability around Europe
No full textMean sea level variability around the European coasts is explored on the basis of regional sea level indices derived through Empirical Orthogonal Function Analysis (EOF) of tidegauge records. The regional indices are cross-correlated amongst themselves and against the major regional and climatic indices. The analysis is done for the whole year as well as seasonally. The effect of coherent atmospheric pressure signals is explored by comparing the results of the analysis before and after the data are corrected for the atmospheric pressure effects. The North Atlantic Oscillation Index (NAO) and the Mediterranean Oscillation Index are the major regional indices which are found to be significantly correlated with sea level variability around Europe. Their correlation is positive for the Northern European coast and negative for the Mediterranean coasts. The NAO influence causes an anti-correlation between northern and southern European sea level. This is stronger in winter and weakens significantly or disappears completely during the summer. When the NAO influence was removed from the regional mean sea level indices the cross correlation between the various regions was reduced. However, residual spatial coherency indicated that probably there are other mechanisms causing spatial coherency. No statistically significant correlation with the Southern Oscillation Index (SOI) was found
Is the Mediterranean Sea surface height variability predictable?
No full textThe relation of sea surface height (SSH) in the Mediterranean Sea with numerous atmospheric variables on time scales from month to few years were investigated in order to construct simple linear statistical models for predicting SSH. Monthly SSH data for the period from January 1993 to December 2001 from the Topex/Poseidon altimetry are used as the dependent variable in models. Numerous large scale atmospheric indices (LSI) as well as gridded fields of various meteorological variables above the Mediterranean region are used as predictors. The annual cycle derived from nine year SSH climatology explains 40% of SSH variance. The statistical models were built on the anomalies from the annual cycle, separated to the following seasons: winter (December–March), spring (April–May), summer (June–September) and autumn (October–November). The results were tested with cross-validation where the quality of the models were judged on the basis of the explained variance of SSH. Among all seasons, SSH was the best predicted in the winter. The most successful LSI, Mediterranean Oscillation Index, is able to explain 46% of winter variance of SSH anomaly from annual cycle (SSHA). The best model, which uses sea level pressure (SLP), northward and eastward components of wind speed at 10 meters above sea level, is able to explain on average 55% of SSHA variance with the values up to 80% in Ionian, Tyrrhenian and eastern part of Algero-Provençal Sea. SSH is the worse predictable in the summer, when the root mean square of SSH is not well above the threshold of its measurements. The SLP and temperature at 2 meters in the atmosphere (T2M) as combined predictors are able to explain 20% of SSHA variance, but only in the Adriatic and Tyrrhenian Seas noticeable part of SSHA could be explained. In spring explained variance of SSHA reaches 38% (when SLP and T2M are used as predictors), while in autumn 28% of SSHA can be explained with SLP as a predictor
Comparison of results of AOGCMs in the Mediterranean Sea during the 21st century
No full textIt is important for policy making to downscale the knowledge derived from global models to smaller areas. However, this is a nontrivial task for the Mediterranean Sea, a semienclosed basin connected to the Atlantic Ocean through the Strait of Gibraltar. The outputs of 12 atmosphere-ocean general circulation models (AOGCMs) in the Mediterranean Sea are used to examine temperature (T), salinity (S), and sea level changes for the 21st century under three different climate scenarios (committed climate change, SRES A1B, and SRES A2). Warming and salinification are predicted to occur in the basin. The T increases are translated into an average thermosteric sea level rise between 3 and 61 cm over the basin. Under A1B and A2 scenarios, thermosteric sea level rise is accelerated. Under the committed climate change scenario the thermosteric sea level, although increasing, is decelerated. In the Mediterranean, S has a large impact in sea level changes, and projections of steric sea level range between ?22 and 31 cm. The contribution of future atmospheric pressure changes on sea level in the Mediterranean Sea is a reduction of up to 0.6 cm. The 20th century model runs indicate that low-frequency variability is smaller than that observed. The spatial patterns of steric sea level change are not consistent among the AOGCMs in the region. Overall, results indicate large uncertainties regarding the combined effects of T and S on future Mediterranean mean sea level changes based on these simulations, with even greater discrepancies on the patterns of change. <br/
Sea level extremes in the Caribbean Sea
Full text linkSea level extremes in the Caribbean Sea are analyzed on the basis of hourly records from 13 tide gauges. The largest sea level extreme observed is 83 cm at Port Spain. The largest nontidal residual in the records is 76 cm, forced by a category 5 hurricane. Storm surges in the Caribbean are primarily caused by tropical storms and stationary cold fronts intruding the basin. However, the seasonal signal and mesoscale eddies also contribute to the creation of extremes. The five stations that have more than 20 years of data show significant trends in the extremes suggesting that flooding events are expected to become more frequent in the future. The observed trends in extremes are caused by mean sea level rise. There is no evidence of secular changes in the storm activity. Sea level return periods have also been estimated. In the south Colombian Basin, where large hurricane-induced surges are rare, stable estimates can be obtained with 30 years of data or more. For the north of the basin, where large hurricane-induced surges are more frequent, at least 40 years of data are required. This suggests that the present data set is not sufficiently long for robust estimates of return periods. ENSO variability correlates with the nontidal extremes, indicating a reduction of the storm activity during positive ENSO events. The period with the highest extremes is around October, when the various sea level contributors' maxima coincide
Sea-level trends and interannual variability in the Caribbean Sea
No full textSea-level trends and their forcing have been investigated in the Caribbean Sea using altimetry and tide gauge time series from 19 stations. The basin average sea level rise is 1.7±1.3 mm y-1 for the period 1993-2010. Significant spatial variability of the trends is found. The steric variability above 800 m combined with the Global Isostatic Adjustment explains the observed trends for the altimetry period in most of the basin. Wind forcing changes causes the trends in the southern part of the basin, modulating the sea level through changes in the ocean circulation. The longest time series (102 y) of Cristobal shows a trend of 1.9±0.1 mm y-1 insignificantly different from the global mean sea level rise for the 20th century. By contrast Cartagena, a world heritage site, has a large trend (5.3±0.3 mm y-1) significantly affected by local vertical land movements. Stations dominated by the steric contribution have smaller trends (~ 1.3±0.2 mm y-1). Sea-level trends at tide gauges are not affected by atmospheric pressure changes or by the open ocean steric contribution at most stations. Decadal variability in the sea-level trends can partly be explained by steric and wind variability. The decadal variability in the trends is not spatially coherent. Interannual sea level variability accounts for 1/3 of the total sea level variability and can be partly explained by the influence of El Niño-Southern Oscillation (ENSO) at different time and spatial scales. No correlation with the North Atlantic Oscillation (NAO) is found
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