Sea level extremes in the Caribbean Sea

Sea 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

Decadal variability of European sea level extremes in relation to the solar activity

This study investigates the relationship between decadal changes in solar activity and sea level extremes along the European coasts and derived from tide gauge data. Autumn sea level extremes vary with the 11 year solar cycle at Venice as suggested by previous studies, but a similar link is also found at Trieste. In addition, a solar signal in winter sea level extremes is also found at Venice, Trieste, Marseille, Ceuta, Brest, and Newlyn. The influence of the solar cycle is also evident in the sea level extremes derived from a barotropic model with spatial patterns that are consistent with the correlations obtained at the tide gauges. This agreement indicates that the link to the solar cycle is through modulation of the atmospheric forcing. The only atmospheric regional pattern that showed variability at the 11 year period was the East Atlantic pattern

Interannual variations in precipitation: the effect of the North Atlantic and Southern oscillations as seen in a satellite precipitation data set and in models

Precipitation is a parameter that varies on many different spatial and temporal scales. Here we look at interannual variations associated with the North Atlantic Oscillation (NAO) and the Southern Oscillation (SO), comparing the spatial and temporal changes as shown by three data sets. The Global Precipitation Climatology Project (GPCP) product is based upon satellite data, whereas both the National Centers for Environmental Prediction (NCEP) and European Centre for Medium-Range Weather Forecasts (ECMWF) climatologies are produced through reanalysis of atmospheric circulation models. All three products show a consistent response to the NAO in the North Atlantic region, with negative states of the NAO corresponding to increases in precipitation over Greenland and southern Europe, but to a decrease over northern Europe. None of the climatologies display any net change in total rainfall as a result of the NAO, but rather a redistribution of precipitation patterns. However, this redistribution of rain is important because of its potential effect on oceanic overturning circulation. Similarly, all three data sets concur that the SO has a major effect on precipitation in certain tropical regions; however, there is some disagreement amongst the data sets as to the regional sensitivity, with NCEP showing a much weaker response than GPCP and ECMWF over Indonesia. The GPCP and NCEP climatologies show that the various phases of El Niño and La Niña act to redistribute, rather than enhance, the freshwater cycle. Given that the models incorporate no actual observations of rain, and are known to be imperfect, it is surprising how well they represent these interannual phenomena

Sea level extremes at the coasts of China

Hourly sea level records from 1954 to 2012 at twenty tide gauges at and adjacent to the Chinese coasts are used to analyse extremes in sea level and in tidal residual. Tides and tropical cyclones determine the spatial distribution of sea level maxima. Tidal residual maxima are predominantly determined by tropical cyclones. The 50-year return level is found to be sensitive to the number of extreme events used in the estimation. This is caused by the small number of tropical cyclone events happening each year which lead to other local storm events included thus significantly affecting the estimates. Significant increase in sea level extremes is found with trends in the range between 2.0-14.1 mm yr-1. The trends are primarily driven by changes in median sea level but also linked with increases in tidal amplitudes at three stations. Tropical cyclones cause significant interannual variations in the extremes. The interannual variability in the sea level extremes is also influenced by the changes in median sea level at the north and by the 18.6-year nodal cycle at the South China Sea. Neither of PDO and ENSO is found to be an indicator of changes in the size of extremes, but ENSO appears to regulate the number of tropical cyclones that reach the Chinese coasts. Global mean atmospheric temperature appears to be a good descriptor of the interannual variability of tidal residual extremes induced by tropical cyclones but the trend in global temperature is inconsistent with the lack of trend in the residuals

The attenuation of waves under the action of rain

The 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 &upsilon;E. All the experiments seem consistent with a value of &upsilon;E 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

Comparison of results of AOGCMs in the Mediterranean Sea during the 21st century

It 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/

The forcing of mean sea level variability around Europe

Mean 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

Shipowner's limitation of liability

At 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