On Tidal Modulation of the Evolution of Internal Solitary-Like Waves Passing Through a Critical Point

Internal solitary-like waves (ISWs) evolve considerably when passing through a critical point separating the deep water where ISWs are waves of depression and shallower water where they are waves of elevation. The location of the critical point is determined by the background current and stratification. In this study, we investigate the influence of tidal currents on the cross-shelf movement of the critical point and elucidate the underlying processes via fully nonlinear numerical simulations. Our simulations reveal phase-locked tidal variations of the critical point, which are mainly attributed to stratification fluctuations that are modulated by the combined effects of cross-shelf barotropic tidal currents and locally generated baroclinic tides. The barotropic tidal currents drive isopycnal displacements as they flow over the slope, and as this occurs baroclinic tides are generated, modulating the stratification and inducing sheared currents. This results in a cross-shelf movement of the critical point, which moves onshore (offshore) when the pycnocline is elevated (depressed) by the flood (ebb) tide. Our idealized numerical simulations for the study region in the South China Sea suggest that the cross-shelf movement of the critical point reaches to O(10) km within a tidal cycle. This distance depends on the strength of tidal currents, stratification, and bathymetry. Because of tidal currents, ISWs of depression may undergo a complex evolution even in a stratification with a shallow pycnocline. For the stratification with a deep pycnocline, the critical point may be at a location deep enough so that its tidal movement becomes insignificant.

Handling Solution Tidal Flood in Kaligawe Area by Polder System Drainage

Kaligawe area is one of the main routes of North Java Coastal traffic and also the gateway of Semarang city from the east. Since more than 5 years this area proned by flooding due to a combination of land subsidence, increasing influence by tidal movement from sea the inability of free flow discharge of river water. In periods of flooding long traffic jams occur for more than 10 kilometers in length. The purpose of this research is to map the flood problem in Kaligawe area, identify the causes of flooding, analyze the technical handling solution and formulate the measures to prevent the flooding in this region. The research method is based on detailed field survey, measurement and observations of water levels, secondary data collection that consist of land subsidence’s, rainfall intensities, tidal elevation. The data are analyzed qualitatively and quantitatively. Among the results of this study is to formulate measures to prevent the number and degree of flooding. These measures can be divided in short, medium term and long term stages. The short term measures consist of construct a temporary weir to regulate water discharge and pump installation including pump strategy. The medium term stage consists of making a polder system, the long term stage consists of spatial sustainability and institutional management of Operation and Maintenance of Polder system.

Posisi komponen GPP terhadap variasi konstituen harmonik pasang surut bulan Muharram di Stasiun Sabang

The movement of celestial bodies produces a variation of a gravitational gradient as a tidal generation force (GPP). Position Sabang Station, declination maximum and position lunar month of Muharram aka n generate harmonic constituent character identifier of GPP, where the water level is the sum of the amplitude of harmonic constituent that generated at a certain time.This research is to determine the variation of harmonic constituents and identify the character of harmonic constituents of GPP component position characterization in Muharram month. The results show Katrakteristik tidal movement beginning of the month of Muharram in Sabang Station occurred 1-2 hours after ijtimak.. Value riding dominant water derived from the value of Mean Sea Level ( 52%), and the dominant contribution hamonik constituents derived from component M 2 (28 - 33%). Harmonic constituents M 2 does not show the position of the moon in Muharram, while the position of the sun is reflected in the constituent phase harmonic S 2..

Indikator Penciri Penanggalan Hijriah pada Pergerakan Pasang Surut

Rhythmic movement of the tides follow the movement of the moon,as the dominant component of which has a rhythmic, should the movement of tidal inform month trip in the form of style variations of tide generating force (GPP) which indicates the time in the Hijra calendar. This article aims to determine the indicator of the tidal movement indicating the time of the Hijri calendar. The timing of slack water (t sw) the movement receded into pairs (tsw s) in peak II relatively consistent for the three months of data were analyzed tidal movement. Consistency is shown on the results of the statistical analysis by comparing the Probability (Pr) to the Wilks’ Lambda ( ) is very small(<0.0001) which means that the time of slack water (t sw) can be a primary identifier in determining the Hijra calendar. Further research is needed to determine the time point t SWS belt of a general nature in order to facilitate the determination of the Hijra calendar through the movement of the tides.DOI: 10.15408/ajis.v17i2.5686

ETHNOOCEANOGRAPHY DAN TITIK TEMU ASPEK SYAR’I DALAM PENENTUAN AWAL BULAN RAMADHAN DAN SYAWAL OLEH JOGURU KESULTANAN TIDORE

<p class="IABSSS">Ethnooceanography and the intersection of <em>shar'i</em> aspects to determination of the early of Ramadan and Shawwal by Joguru Sultanate of Tidore.<em> </em>The determination of the early of the new month of Ramadan and Shawwal was very important for Muslims because it is related to the time of worship. Judge syara 'The Sultanate of Tidore (Joguru) has long applied the method of determining the early month of Hijri (Ramadan and Shawwal) through tidal movement observed on "akebai" included in ethooceanography and called Joguru Method (MJ). Hilal that has never been seen in Tidore and its surrounding areas in the long-term cycle of moon (34 years) caused its early moon to be inapplicable due to non-fulfillment of the requirement of hisab (hadith). MJ makes observation (rukyat) change of tidal movement on "akebai" is "<em>ijtihād</em>". The appropriateness of the scientific aspects of ethnoocaenography and the intersection of the <em>shar'i</em> aspects make it a comparative method of determining the beginning of the new month of Hijri in astronomy (<em>hilāl</em>). Required the expansion of the meaning of the “<em>hilāl</em>” as an indicator of the beginning of the month of the Hijri calendar.</p><p class="IABSSS" align="center">[]</p><em>Ethnooceanography</em> dan titik temu aspek Syar’i dalam penentuan awal bulan Ramadhan dan Syawal oleh Joguru Kesultanan<em> </em>Tidore. Penentuan awal bulan baru Ramadhan dan Syawal sangat penting bagi umat Islam karena berkaitan dengan waktu ibadah. Hakim syara’ Kesultanan Tidore (Joguru) telah lama mengaplikasikan metode penentuan awal bulan baru Hijriah (Ramadhan dan Syawal) melalui pergerakan pasang surut yang terpantau pada “akebai” termasuk dalam e<em>thooceanography </em>dan disebut dengan Metode Joguru (MJ)<em>. </em>Hilal yang tidak pernah terlihat di wilayah Tidore dan sekitarnya selama siklus jangka panjang (34 tahun) menyebabkan hisab awal bulan tidak dapat diaplikasikan akibat tidak terpenuhinya persyaratan hisab (hadis). MJ melakukan peng­amatan (rukyat) perubahan tinggi air pada “akebai” adalah “ijtihad”. Terdapat ke­sesuaian aspek sains dari <em>ethnoocaenography</em> serta titik temu aspek syar’i yang menjadikan MJ berpotensi sebagai metode utama sekaligus sebagai metode pem­banding dari metode umum dalam penentuan awal bulan baru Hijriah. Diperlukan perluasan makna kata “hilal” sebagai indikator awal bulan baru penanggalan Hijriah.

THE NATURAL DEVELOPMENT OF THE WADDEN SEA AFTER THE ENCLOSURE OF THE ZUIDER SEA

The Wadden Sea and Zuider Sea used to form an internal sea which was separated from the North Sea by a chain of islands. In 1932 the Zuider Sea was enclosed by a dam 32 km in length. Owing to this, the Wadden Sea experienced changes in the normal tidal movement, the storm-surge levels and the configuration of the bed. This article discusses the movement of water and sand the Wadden Sea and its natural development since the enclosure of the Zuider.

INVESTIGATIONS OF THE TIDES AND STORM SURGES FOR THE DELTAWORKS IN THE SOUTHWESTERN PART OF THE NETHERLANDS

In order to protect the southwestern part of the Netherlands against inundation by storm surges, the "Delta project" has been undertaken. This entails the closure of three large sea arms situated between Western Scheldt and Rotterdam Waterway and will bring about radical changes in the tidal movement and stormflood levels of the estuaries and tidal rivers. The contours of the project are shown in fig. 1. It includes three big dams to be built in the mouths of Eastern Scheldt, Brouwershavense Gat and Haringvliet, as well as two smaller ones to be constructed further inland. An idea of the extent of these works may be gained by knowing the tidal volumes of the estuaries: Veerse Gat 2.5.109 cu. ft; Grevelingen 4.109 cu. ft? Haringvliet 9.109 cu. ft; Brouwershavense Gat 12,5.109 cu. ft and Eastern Scheldt 39>.109 ou.ft. The waters of the Delta area will then be divided into two separate basins by means of a dam in the Volkerak. The southern basin will be entirely cut off from the sea, becoming a fresh water lake. The northern, comprising the mouths of the Rhine and the Meuse will remain in communication with the sea, because the Rotterdam Waterway must stay open to shipping. Consequently, the tides and storm surges will still be able to penetrate inland via this mouth, but they can cause high water levels in the Waterway only; in the rest of the basin their effect will be considerably weakened. In the situation at present, however, the upland flow of the rivers Rhine and Meuse is mainly into the Haringvliet estuary and not the Rotterdam Waterway. As the Haringvliet estuary will be closed, large sluices are to be built in the enclosure dam as a substitute for the existing free discharge of the river water. Until this project is completed the inhabitants of the area which it will affect are insufficiently safe against storm surges. It is, of course, always possible that floods too high for existing dike systems will occur, but in the present situation the risk is too great. This was demonstrated in February 1953 when the southwestern part of the Netherlands was suddenly hit by an exceptionally high storm surge which caused many dike breaches and vast inundation. The occurrence of a similar surge or a higher one may be estimated as once in two hundred and fifty years, as an average, which is much too high. After the realization of the Deltaplan and the heightening of the dikes of Western Scheldt, Rotterdam Waterway and the northern parts of the country, the dikes are safe tip to very high storm surges of which the occurrence is smaller than once in ten thousand years, or in other words there is only one procent chance in hundred years that a major inundation will occur.

Tidal Movement Characteristics Outside the Pearl River Estuary and Its Influence on the Mouths

The hydrology of the Pearl River Estuary is controlled both by river discharge and tide, where water and sediment move through eight outlets (mouths) into the sea. Using numerical modeling, this paper examines the characteristics of tidal movement in Pearl River Estuary. Results showed an amphidromic point near Modaomen mouth, and river runoff flows down. From marine dynamics point of view, Modaomen mouth is the main channel for water and sediment transportation of Pearl River. Using the tidal energy, we discuss the change of the sediment near the several entrances during the flood and dry seasons.

Commercial oyster stocks as a potential source of larvae in the regeneration of Ostrea edulis in Strangford Lough, Northern Ireland

Ostrea edulis was extremely rare in the wild in Strangford Lough from the early 1900s until renewed spatfall was observed at a number of sites in the 1990s. A monitoring programme was undertaken to investigate the presence and distribution of planktonic oyster larvae at nine sites around the lough between June and September in 1997 and 1998 as a precursor to studies of spatfall patterns. Larval densities at sites in the northern basin of the lough were significantly higher than those in the southern basin where larvae were lacking or in low numbers. Densities and sizes of oyster larvae showed significant temporal variation suggesting pulsed larval release. Larval densities also showed significant spatial variation with higher densities at sites closer to commercial stocks pointing to these as the main source of oyster larvae. This hypothesis was supported during a larval flux study over a complete tidal cycle which indicated a 90% net tidal movement of O. edulis larvae from the entrance of the bay where commercial stocks were held to the main body of the lough. Thus the maintenance of dense commercial stocks of flat oysters may provide the key to the redevelopment of native oyster beds in Strangford Lough and elsewhere by providing an initial broodstock nucleus from which larvae can be exported.