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"Tidal waves"
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Over the seawall : tsunamis, cyclones, drought, and the delusion of controlling nature
\"As extreme weather becomes more common, the urge to outwit nature can be irresistible. But when our expensive technosolutions backfire, are we worse off than before? How should we adapt to a changing climate? Miller reveals the unintended consequences of bad adaptations or as academics call it, maladaptations--fixes that do more harm than good. From seawalls in coastal Japan, to the reengineered waters in the Ganges River Delta, to the artificial ribbon of water supporting both farms and urban centers in parched Arizona, the author traces the histories of engineering marvels that were once deemed too smart and too big to fail. In each he takes us into the land and culture, seeking out locals and experts to better understand how complicated, grandiose schemes led instead to failure, and to find answers to the technologic holes we've dug ourselves into. Miller urges us to take a hard look at the fortifications we build and how they've fared in the past. He embraces humanity's penchant for problem-solving, but argues that if we are to adapt successfully to climate change, we must recognize that working with nature is not surrender but the only way to assure a secure future.\"--From publisher's description.
Book
Analysis of the tidal wave occurrence on port project duration using crash and track method (case study: Sanur Port, Bali, Indonesia)
One of the main risks that can influence the duration of port projects is the tidal waves. Tidal waves can disrupt the work and cause delays. This study analyzes when a tidal wave occurs and how much it affects the delay in the Sanur Port Project. Based on these results, several scenarios of duration acceleration were carried out using the crashing and fast track methods. The results showed that the planned duration was 819 days, whereas due to the tidal wave, the project duration increased from 98 to 917 days. The first acceleration scenario, using the crashing method with 2 h of overtime, resulted in a new duration of 783 days or 36 days faster than the planned duration. The second acceleration scenario with the fast-track method resulted in 770 or 49 days faster than the planned duration.
Journal Article
Global Observations of Open-Ocean Mode-1 M2 Internal Tides
A global map of open-ocean mode-1 M
2
internal tides is constructed using sea surface height (SSH) measurements from multiple satellite altimeters during 1992–2012, representing a 20-yr coherent internal tide field. A two-dimensional plane wave fit method is employed to 1) suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2) separately resolve multiple internal tidal waves. Global maps of amplitude, phase, energy, and flux of mode-1 M
2
internal tides are presented. The M
2
internal tides are mainly generated over topographic features, including continental slopes, midocean ridges, and seamounts. Internal tidal beams of 100–300 km width are observed to propagate hundreds to thousands of kilometers. Multiwave interference of some degree is widespread because of the M
2
internal tide’s numerous generation sites and long-range propagation. The M
2
internal tide propagates across the critical latitudes for parametric subharmonic instability (28.8°S/N) with little energy loss, consistent with the 2006 Internal Waves across the Pacific (IWAP) field measurements. In the eastern Pacific Ocean, the M
2
internal tide loses significant energy in propagating across the equator; in contrast, little energy loss is observed in the equatorial zones of the Atlantic, Indian, and western Pacific Oceans. Global integration of the satellite observations yields a total energy of 36 PJ (1 PJ = 10
15
J) for all the coherent mode-1 M
2
internal tides. Finally, satellite observed M
2
internal tides compare favorably with field mooring measurements and a global eddy-resolving numerical model.
Journal Article
The characteristics of tides and their effects on the general circulation of the Mediterranean Sea
The effects of tides on the Mediterranean Sea's general circulation, with a particular focus on the horizontal and vertical currents, are investigated using twin simulations with and without tides. Amplitudes of tides in the region are typically low, but an analysis of the potential and kinetic energy demonstrates that tides have effects across many spatial and temporal scales in the basin, including non-linear effects in short periods (less than 1 d) with high kinetic energy peaks at near-inertial basin modes and tidal frequencies. Internal tidal waves are also revealed below 100 m. Tides are found to amplify several basin modes of the Mediterranean Sea, broaden several tidal frequency energy spectra bands, and interact energetically with near-inertial waves. Tides increase the mixed layer depth in the Mediterranean Sea, particularly in the deep and intermediate water formation areas of the western Mediterranean Basin and eastern Mediterranean Basin. The addition of tides in the cases considered does also enhance Western Mediterranean Deep Water formation.
Journal Article
A Variety of Transformations of Nonlinear Internal Tidal Waves of the Northwestern Shelf of Australia
Highly nonlinear internal waves at the continental margin on the northwestern shelf of Australia are discussed using detailed velocity and temperature time series recorded from moored current meters over 67 days. The region is characterized by a vigorous semidiurnal inland tide that propagates towards the shore along the shelf. In this area, an increase in the internal tide and the formation of bore-like formations, often accompanied by internal solitary waves, are observed. The frequency spectrum of the internal waves is presented, calculated from the records of the current component directed along the normal to the coast. Within the framework of this work, we have focused on analysis of the shape and properties of the internal tide. As a result, five different types of waves are distinguished. They consist of bores on the front or back sides of the wave, “square” waveforms with bores on both the front and back sides of the wave simultaneously, as well as small- and large-amplitude linear waves. The statistics of transformations of the types of internal tides during their propagation along the route section from the slope to the shelf is given. The main types of waves propagating without transformation and short-lived waves, which include “square” tidal waves and waves with bores on the back slope of the wave, are revealed. In general, the analysis provided an accurate account of the present-day nonlinear transformations of tidal internal waves on the Northwestern Australian Shelf.
Journal Article
Joint Risk of Rainfall and Storm Surges during Typhoons in a Coastal City of Haidian Island, China
Public health risks from urban floods are a global concern. A typhoon is a devastating natural hazard that is often accompanied by heavy rainfall and high storm surges and causes serious floods in coastal cities. Affected by the same meteorological systems, typhoons, rainfall, and storm surges are three variables with significant correlations. In the study, the joint risk of rainfall and storm surges during typhoons was investigated based on principal component analysis, copula-based probability analysis, urban flood inundation model, and flood risk model methods. First, a typhoon was characterized by principal component analysis, integrating the maximum sustained wind (MSW), center pressure, and distance between the typhoon center and the study area. Following this, the Gumbel copula was selected as the best-fit copula function for the joint probability distribution of typhoons, rainfall, and storm surges. Finally, the impact of typhoons on the joint risk of rainfall and storm surges was investigated. The results indicate the following: (1) Typhoons can be well quantified by the principal component analysis method. (2) Ignoring the dependence between these flood drivers can inappropriately underestimate the flood risk in coastal regions. (3) The co-occurrence probability of rainfall and storm surges increases by at least 200% during typhoons. Therefore, coastal urban flood management should pay more attention to the joint impact of rainfall and storm surges on flood risk when a typhoon has occurred. (4) The expected annual damage is 0.82 million dollars when there is no typhoon, and it rises to 3.27 million dollars when typhoons have occurred. This indicates that typhoons greatly increase the flood risk in coastal zones. The obtained results may provide a scientific basis for urban flood risk assessment and management in the study area.
Journal Article
Enhancing Tidal Wave Predictions for the Estuary of the Nakdong River Using a Fixed-Lag Smoother
The prediction of tidal waves is essential for improving not only our understanding of the hydrological cycle at the boundary between the land and ocean but also energy production in coastal areas. As tidal waves are affected by various factors, such as astronomical, meteorological, and hydrological effects, the prediction of tidal waves in estuaries remains uncertain. In this study, we present a novel method that can be used to improve short-term tidal wave prediction using a fixed-lag smoother based on sequential data assimilation (DA). The proposed method was implemented for tidal wave predictions of the estuary of the Nakdong River. As a result, the prediction accuracy was improved by 63.9% through DA and calibration using regression. Although the accuracy of the DA diminished with the increasing forecast lead times, the 1 h lead forecast based on DA still showed a 44.4% improvement compared to the open loop without DA. Moreover, the optimal conditions for the fixed-lag smoother were analyzed in terms of the order of the smoothing function and the length of the assimilation window and forecast leads time. It was suggested that the optimal DA configuration could be obtained with the 8th-order polynomial as the smoothing function using past and future DA assimilation windows assimilated 6 h or longer.
Journal Article
Satellite Investigation of the M2 Internal Tide in the Tasman Sea
The M
2
internal tide in the Tasman Sea is investigated using sea surface height measurements made by multiple altimeter missions from 1992 to 2012. Internal tidal waves are extracted by two-dimensional plane wave fits in 180 km by 180 km windows. The results show that the Macquarie Ridge radiates three internal tidal beams into the Tasman Sea. The northern and southern beams propagate respectively into the East Australian Current and the Antarctic Circumpolar Current and become undetectable to satellite altimetry. The central beam propagates across the Tasman Sea, impinges on the Tasmanian continental slope, and partially reflects. The observed propagation speeds agree well with theoretical values determined from climatological ocean stratification. Both the northern and central beams refract about 15° toward the equator because of the beta effect. Following a concave submarine ridge in the source region, the central beam first converges around 45.5°S, 155.5°E and then diverges beyond the focal region. The satellite results reveal two reflected internal tidal beams off the Tasmanian slope, consistent with previous numerical simulations and glider measurements. The total energy flux from the Macquarie Ridge into the Tasman Sea is about 2.2 GW, of which about half is contributed by the central beam. The central beam loses little energy in its first 1000-km propagation, for which the likely reasons include flat bottom topography and weak mesoscale eddies.
Journal Article
Influence of Sea Level Rise on Tidal Waves of the Yangtze River Estuary
In order to study the influence of sea level rise (SLR) on tidal wave in tidal reach, a hydrodynamic numerical model of the Yangtze River Estuary was established using MIKE 21. The verified model was used to simulate tidal wave changes from Wuhu to the estuary under SLR scenarios of 0.5 m, 1.0 m, and 2.0 m. The results show the following: (1) The impact of SLR on water level within the tidal reach can be divided into two segments: from the estuary to approximately 35 km upstream of Xuliujing and from there further upstream to the tidal limit. (2) The average water level increase is less than the magnitude of SLR. The attenuation depends on both river discharge and location within the reach; higher river discharge and increasing proximity to inland areas reduce the influence of SLR. (3) Water level fluctuation amplitude increases with SLR, showing minimal sensitivity to river discharge within the estuarine section but significant sensitivity to discharge fluctuations in the upstream section. Finally, tidal current velocity generally increases in response to SLR, with the spatial extent of the increase controlled by river discharge.
Journal Article
Spatial Distribution of Internal Tidal Waves on the Northeastern Shelf of Sakhalin
The transformation of a multicomponent barotropic tide in the Sea of Okhotsk is considered in the framework of fully nonlinear nonhydrostatic calculations. The data on the tidal model and parametrizable bottom topography and seawater density vertical profiles based on open international atlases are used to initialize the model. The wave amplitude values obtained of the diurnal and semidiurnal baroclinic tides in terms of the displacement of isopycnal surfaces at different depth levels are presented as geographical maps. It is shown that the amplitude distribution depends significantly on depth and has a complex spatial structure with a noticeable predominance of diurnal baroclinic wave amplitudes and the main extrema located on the shelf opposite to Cape Elizabeth, Okhinskii Isthmus, and Cape Patience. The implemented approach to mapping the internal tide amplitudes can be applied to other shelf areas of the seas of the Russian Federation and used for predictions of these phenomena, including engineering assessments for the design and management of marine infrastructure.
Journal Article