79 research outputs found
Spatial distribution of water level impacting back-barrier bays
No full text© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aretxabaleta, A. L., Ganju, N. K., Defne, Z., & Signell, R. P. Spatial distribution of water level impacting back-barrier bays. Natural Hazards and Earth System Sciences, 19(8), (2019): 1823-1838, doi: 10.5194/nhess-19-1823-2019.Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a complementary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Bay area and inlet geometry and bathymetry primarily regulate the magnitude of the transfer between open ocean and bay. Tides and short-period offshore oscillations are more damped in the bays than longer-lasting offshore fluctuations, such as a storm surge and sea level rise. We compare observed and modeled water levels at stations in a mid-Atlantic bay (Barnegat Bay) with offshore water level proxies. Observed water levels in Barnegat Bay are compared and combined with model results from the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system to evaluate the spatial structure of the water level transfer. Analytical models based on the dimensional characteristics of the bay are used to combine the observed data and the numerical model results in a physically consistent approach. Model water level transfers match observed values at locations inside the bay in the storm frequency band (transfers ranging from 50 %–100 %) and tidal frequencies (10 %–55 %). The contribution of frequency-dependent local setup caused by wind acting along the bay is also considered. The wind setup effect can be comparable in magnitude to the offshore transfer forcing during intense storms. The approach provides transfer estimates for locations inside the bay where observations were not available, resulting in a complete spatial characterization. An extension of the methodology that takes advantage of the ADCIRC tidal database for the east coast of the United States allows for the expansion of the approach to other bay systems. Detailed spatial estimates of water level transfer can inform decisions on inlet management and contribute to the assessment of current and future flooding hazard in back-barrier bays and along mainland shorelines.This work was supported by the US Geological Survey, Coastal and Marine Hazards/Resources Program
Polarization in neutron-proton elastic scattering at 21.6 MEV
No full textBibliography: leaves 102-106.The polarization in n-p scattering has been measured at 21.6 MeV using polarized neutrons from the T(d,ṅ)4He reaction. The measuring instrument was an anthracene scintillation polarimeter. A critical assessment of this polarimeter was made, and extensive refinements to the polarimeter were introduced so as to minimise perceived sources of systematic error. These included improvements both in instrumental design and data reduction techniques
Tide- and wind-forced currents in Buzzards Bay, Massachusetts
No full textThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987.Microfiche copy available in Archives and Science.Bibliography: leaves 83-86.by Richard Peter Signell.M.S
Intelligent Equalisation Principles and Techniques for Minimising Masking when Mixing the Extreme Modern Metal Genre.
No full textThe intensity, complexity and energy of performance, combined with the power and density of the tones involved are characteristics of the extreme metal genre. These characteristics present numerous problems when striving to achieve the clarity, definition and hyper-realism of performance required for this genres production. Avoiding masking in a mix is a fundamental
aspect of clarity, definition, intelligibility and perceived loudness and due to the fact that masking especially occurs in a dense mix, and is more pronounced in low frequencies, is particularly applicable to mixing the downtuned extreme metal genre. Masking in simple terms is the ability of frequencies of one sound to obscure or inhibit (i.e. mask) the frequencies of
another sound. This paper will draw upon the first author’s eight years of experience producing within the metal genre, including releases through Sony and Universal and working with the likes of Colin Richardson and Andy Sneap
Hydrographic study of Buzzards Bay, 1982-1983
No full textA series of four hydrographic cruises at three-month intervals was
undertaken in Buzzards Bay in 1982-83. Buzzards Bay is located on the
southern coast of Massachusetts, west of Cape Cod. Listings and vertical
profiles of one-meter-averaged values of temperatures, salinity, sigma-t
and light transmission are presented. Selected vertical cross-sections
of temperature, salinity and sigma-t are also included, as are horizontal
maps of the same variables at depths of 1 m and 8 m.Prepared for NOAA, National Sea Grant College Program, under grant
numbers NA80-AA-D-0007 (R/P-16; R/P-15) and NA83-AA-D-00049
(R/P-13) and the Coastal Research Center under a grant from the Andrew
W. Mellon Foundation
Determining potential for pollutant impacts in dynamic coastal waters: comparing morphological settings
No full textThe coastal focus and beach culture of Australia’s population in general, and the people of New South Wales in particular, mean that coastal systems are both highly prized and subjected to great pressures. The vast majority of the wastewater generated by the 7.3 million people of New South Wales is discharged directly to the ocean. The dispersion and fate of waterborne pollutants and their potential to impact coastal ecosystems are fundamentally determined by the dynamics of the coastal boundary layer (CBL). This turbulent interface between the coastline and the deep oceans is defined and classified for the first time in this thesis. Coastal morphologies and changes in the orientation of the coastline promote turbulence and strong gradients with extreme variability and heterogeneity over a broad range of scales. Conceptual models are presented to characterise New South Wales coastal boundary layer processes.
The broad aims of this thesis are to investigate the coastal boundary layer processes that affect dispersal and advection of pollutants, and to develop conceptual models and tools to facilitate coastal management.
Remote sensed ocean colour and sea surface temperature observations define meso-scale CBL phenomena, and this study demonstrates their application to support management decisions in relation to marine algal (phytoplankton) blooms. However, considerable scope exists to improve regional algorithms to deliver better ocean colour products for the optically complex (Case 2) waters of the inner coastal boundary layer.
Past failures to consider the CBL (morphological) settings of pollutant discharges to coastal waters have led to inefficient pollutant discharge systems and potential environmental impacts. Two case studies, investigate the principal forcing mechanisms and demonstrate the importance of morphology in controlling the dispersion and retention times of pollutants.
The first case study is focused on Sydney coastal waters where pollutant loadings are greater in magnitude and different in character than elsewhere in New South Wales. Here population pressures generate large wastewater loadings but the distances to offshore discharge locations are large compared to the scale of coastal roughness (headlands and bays) and the water is deep, thus reducing the risk of local retention of pollutants and increasing the potential for rapid dilution. By considering simulations of near field effluent plume behaviour in relation to long term ambient nutrient patterns specific periods of the year and depth intervals have been identified when outfalls would have an increased opportunity to influence bloom development, especially the upper half of the water column during late summer. However, algal blooms appear to be principally driven by seasonal oceanic nutrient enrichment. The research presented in this thesis, together with companion research previously published by the author and routine ongoing monitoring, indicate the viability of disposal of the Sydney’s excess sewage effluent (after source control and re-use options have been exhausted) via existing deepwater outfalls.
In contrast, inner CBL settings with coastal irregularities (e.g. headlands and bays) have a greater propensity to trap pollutants. A new hydrodynamically relevant morphological classification of New South Wales bays, headlands and islands provides both broad context for case studies and guides preliminary assessments for other locations. This classification reveals a borderline propensity for flow separation and re-circulation in the lee of Corambirra Point which is the focus of the second case study off Coffs Harbour in northern NSW. Direct observations and 3D finite difference hydrodynamic (Eulerian) and particle tracking (Lagrangian) model simulations quantify transient re-circulation associated with local current accelerations and a persistent shear zone located in the wake to the south of Corambirra Point. The flux of ambient water across the prescribed outfall alignment increases eighteen fold, over a shear zone spanning a cross-shore distance of just 1.4km (from 1.6km to 3km offshore). In contrast, the potential for re-entrainment and trapping of effluent in transient re-circulation cells was demonstrated to be insignificant. The proposed location of the outfalls was 1.5km offshore whereas the greatest gain per unit extension of the proposed discharge point coincides with the centre of the shear zone located ~2km offshore.
These case studies illustrate specific coastal boundary layer effects and indicate how an understanding of the spatial and temporal scales of these effects can be used to target more specific assessments of potential pollutant impacts. Simple morphological risk assessment tools are also presented to identify factors and processes which limit the exposure of sensitive environments to high pollutant concentrations and loads. Eddy retention effects are generally not incorporated in existing near field models but potential re-entrainment effects in wake zones can be assessed through the eddy retention value, which is introduced in this thesis. Although the approach presented here is focused on New South Wales coastal waters, the framework serves as a basis for general application elsewhere, and as a foundation for further refinement for application to NSW coastal waters.
Existing scientific literature indicates that coastal boundary layer processes also shape the distributions of the biological species and communities. This further motivates the development of a process based understanding of coastal boundary layer dynamics as a fundamental platform to support environmental protection and biodiversity conservation initiatives
Rotating gravity currents: small-scale and large-scale laboratory experiments and a geostrophic model
No full textLaboratory experiments simulating gravity-driven coastal surface currents produced by estuarine fresh-water discharges into the ocean are discussed. The currents are generated inside a rotating tank filled with salt water by the continuous release of buoyant fresh water from a small source at the fluid surface. The height, the width and the length of the currents are studied as a function of the background rotation rate, the volumetric discharge rate and the density difference at the source. Two complementary experimental data sets are discussed and compared with each other. One set of experiments was carried out in a tank of diameter 1 m on a small-scale rotating turntable. The second set of experiments was conducted at the large-scale Coriolis Facility (LEGI, Grenoble) which has a tank of diameter 13 m. A simple geostrophic model predicting the current height, width and propagation velocity is developed. The experiments and the model are compared with each other in terms of a set of non-dimensional parameters identified in the theoretical analysis of the problem. These parameters enable the corresponding data of the large-scale and the small-scale experiments to be collapsed onto a single line. Good agreement between the model and the experiments is found
LiLaS
No full textThis paper describes a generic link layer simulation environment for multiple antenna systems in MATLAB and OCTAVE, for both Windows and Unix/Linux operating systems: LiLaS. The simulator is functionally divided into modules, sub-modules and models with a common interface for the convenience of modification and reconfiguration. Currently, it accommodates a variety of transmission schemes, including single-carrier and multiple-carrier MIMO, Orthogonal Frequency-Division Multiplexing (OFDM), OFDM/Offset QAM, Wideband Code Division Multiple Access (W-CDMA), filtered multitone (FMT) and RFID which have extensive applications in modern communication technologies, e.g.. WLAN 802.11 a/b/g/n, WiMAX, UWB, 3G, LTE, LTE advanced, IMT advanced, xDSL, DVB, etc.</p
Technical note: Harmonising metocean model data via standard web services within small research groups
No full textWork over the last decade has resulted in standardised web services
and tools that can significantly improve the efficiency and
effectiveness of working with meteorological and ocean model
data. While many operational modelling centres have enabled query and
access to data via common web services, most small research groups
have not. The penetration of this approach into the research
community, where IT resources are limited, can be dramatically
improved by (1) making it simple for providers to enable web service
access to existing output files; (2) using free technologies that are
easy to deploy and configure; and (3) providing standardised, service-based tools that work in existing
research environments. We present
a simple, local brokering approach that lets modellers continue to use
their existing files and tools, while
serving virtual data sets that can be used with standardised tools.
The goal of this paper is to convince modellers that a standardised framework is not
only useful but can be implemented with modest effort using free software components. We use
NetCDF Markup language for data aggregation and standardisation, the
THREDDS Data Server for data delivery, pycsw for data search, NCTOOLBOX
(MATLAB®) and Iris (Python)
for data access, and Open Geospatial Consortium Web Map Service for
data preview. We illustrate the effectiveness of this approach with
two use cases involving small research modelling groups at NATO and
USGS
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