Surface Current

The morphological and climatic conditions of the Atlantic coast of northern Portugal result in a prevailing upwelling circulation over the continental shelf. A submarine outfall releases wastewater into the ocean c. 3 km directly offshore (at ~16 m water depth) from S. Jacinto, 5 km to the north of the inlet to the estuarine coastal lagoon system of the Ria de Aveiro. The buoyant plume has a distinctive reddish brown colour and is clearly visible at the water surface. The transport and dispersion of the plume was monitored by airborne photography and by in situ water sampling. Results revealed the surface currents present and water mass fronts in the nearshore zone of the Aveiro coast. During the spring and summer, the plume was not transported offshore in the manner expected by the upwelling shelf circulation. Instead, it was commonly observed to be transported alongshore with the prevailing southerly circulation or with an onshore component. The transport to the south caused the outfall plume to interact with the circulation associated with the tidal currents generated in the inlet channel to the Ria de Aveiro. The observations suggest that the trophic status of the Ria de Aveiro is unlikely to change because of the operation of the submarine outfall. Furthermore, this study demonstrates how simple observations of wastewater discharge from a submarine outfall can be used to improve understanding of nearshore circulation.

The radiation as well as antenna efficiency of very thin profile zeroth-order resonator (ZOR) antenna, implemented in negative phase velocity (NPV) microstrip transmission line (TL) structure, has been solved by the method of moment simulator IE3D. The radiation is investigated using individual portions of the ZOR antenna that shows significant values of the surface current density. Dominantly radiating parts have been identified, geometrically emphasized by means of the increase in the antenna height over the ground plane from 1/105 to 1/8 λ 0 . The measured parameters of the improved antenna prototype have been enhanced so they reached the following values (compared to original ones): gain 5.0 dBi (-3.0 dBi), antenna efficiency 97.7 % (9.5 %).

Algeciras Bay constitutes a physical environment of special characteristics, due to its bathymetric configuration and geographical location, at the eastern boundary of the Strait of Gibraltar. Hence, the Bay is subject to the complex hydrodynamics of the Strait of Gibraltar, characterized by a mesotidal, semidiurnal regime and the high density-stratification of the water column due to the presence of the

Allozyme variation of 30 populations of the amphipod Talitrus saltator collected from different localities of Atlantic and Mediterranean coasts was studied. A remarkable genetic differentiation was revealed among diverse geographic groups. Three main groups were highlighted showing values of genetic distance (average D = 0.4) frequently reported for interspecific comparisons. The estimates of gene flow calculated from the Fst values are reported. The pattern of genetic divergence between the different geographic groups is discussed taking into account the dispersal capacity of T. saltator, the pattern of the surface currents in the Mediterranean basin and the Pleistocene climatic fluctuations in the Mediterranean.

A time series of velocity profile in the upper 150 m of the equatorial Atlantic was gathered at 23W in 2002 within the PIRATA program. It constitutes the first time series of near surface current measurements simultaneous with altimetric data in the equatorial Atlantic. The surface slope anomaly along the equator is computed from satellite altimetry, and, as a proxy for the pressure gradient along the equator, compared with the wind and near surface current data. In a first step, a time series of the surface slope anomaly along the equator in the Atlantic is computed from the 10 year long TOPEX/Poséïdon sea level anomalies. A sensitivity study establishes the robustness of the calculation. Apart from a 15 cm bias, the equatorial sea surface slope anomalies estimated either from TOPEX/Poséïdon or from Jason over the 6 month overlap (Feb -Aug 2002) do not reveal drastic differences. We produce two sea surface slope anomaly composite time series for 2002 (one with T/P data, the other with Jason data during the commissioning phase) and compare them to the wind and velocity data at 23W. As expected, the near surface velocity and depth of the upper limit of the equatorial undercurrent (EUC) are extremely well correlated with the surface pressure gradient anomaly. 10 year long time series of altimetry derived zonal sea surface slope anomaly and ECMWF ERA40 wind stress are also well correlated. They exhibit similar spectral content and similar anomalous years. This is a first step towards a full analysis of the EUC dynamics using altimetry, PIRATA data (near surface current and subsurface thermohaline structure) and model. These initial comparisons reinforce the utility of Jason measurements for continuing the 10year and highly accurate TOPEX/Poseïdon time series for study of equatorial signals.

Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr 3 , CH 2 Br 2 , CHCl 2 Br, CHClBr 2 , and CH 2 BrCl, were measured in the Strait of Malacca and the South China and Sulu-Sulawesi seas during a two-month research cruise in June-July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of northern Borneo. CHBr 3 was the most abundant bromocarbon, ranging from 5.2 pmol mol -1 in the Strait of Malacca to 0.94 pmol mol -1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8-1.3 pmol mol -1 for CH 2 Br 2 , 0.1-0.5 pmol mol -1 for CHCl 2 Br, and 0.1-0.4 pmol mol -1 for CHClBr 2 . There was no significant correlation between bromocarbons and in situ chlorophyll a, but positive correlations with both MODIS and SeaWiFS satellite chlorophyll a. Together, the shortlived bromocarbons contribute an average of 8.9 pmol mol -1 (range 5.2-21.4 pmol mol -1 ) to tropospheric bromine loading, which is similar to that found in previous studies from global sampling networks . Statistical tests showed strong Spearman correlations between brominated compounds, suggesting a common source. Log-log plots of CHBr 3 /CH 2 Br 2 versus CHBr 2 Cl/CH 2 Br 2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to Published by Copernicus Publications on behalf of the European Geosciences Union. 8138 M. S. Mohd Nadzir et al.: Bromocarbons in the tropical ocean atmosphere during PESC 09 make a crude estimate of the regional emissions of CHBr 3 and to derive a value of 32 Gg yr -1 for the Southeast (SE) Asian region (10 • N-20 • S, 90-150 • E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

A detailed Pliocene oxygen isotope record from the Ontong Java Plateau, based on measurements of the surface-dwelling planktonic foraminifer Globigerinoides sacculifer, was produced for the period from 5 to 2 Ma. The record documents major long-and short-term climate changes. The results show periods of enhanced ice volume at 4.6 to 4.3 Ma and after 2.85 Ma, a long-term warming trend from 4.1 to 3.7 Ma, and a distinct cooling trend that was initiated at 3.5 Ma and progressed through the initiation of large-scale Northern Hemisphere glaciation after 2.85 Ma (according to the time scale of Shackleton and others proposed in 1990). Periods of high average ice volumes also show the highest δ 18 θ amplitudes. The pattern of climate cyclicity changed markedly at about 2.85 Ma. Earlier times were marked by high-frequency variability at the precessional frequencies or even higher frequencies, pointing to low-latitude processes as a main controlling factor driving planktonic δ 18 θ variability in this period. The high-frequency variability is not coherent with insolation and points to strong nonlinearity in the way the climate system responded to orbital forcing before the onset of large scale Northern Hemisphere glaciation. After 3 Ma, stronger 41-k.y. cyclicity appears in the record. The shift in pattern is clearest around 2.85 Ma (according to the time scale proposed by Shackleton and others in 1990), 100-200 k.y. before the most dramatic spread of Northern Hemisphere ice sheets. This indicates that high-latitude processes from this point on began to take over and influence most strongly the δ 18 θ record, which now reflects ice-volume fluctuations related to the climatic effects of obliquity forcing on the seasonality of high-latitude areas, most probably in the Northern Hemisphere. The general Pliocene trend is that high-latitude climate sensitivity and instability was increasing, and the causal factors producing the intensified glacial cyclicity during the Pliocene must be factors that enhance cooling and climate sensitivity in the subarctic areas.

A detailed Pliocene oxygen isotope record from the Ontong Java Plateau, based on measurements of the surface-dwelling planktonic foraminifer Globigerinoides sacculifer, was produced for the period from 5 to 2 Ma. The record documents major long-and short-term climate changes. The results show periods of enhanced ice volume at 4.6 to 4.3 Ma and after 2.85 Ma, a long-term warming trend from 4.1 to 3.7 Ma, and a distinct cooling trend that was initiated at 3.5 Ma and progressed through the initiation of large-scale Northern Hemisphere glaciation after 2.85 Ma (according to the time scale of Shackleton and others proposed in 1990). Periods of high average ice volumes also show the highest δ 18 θ amplitudes. The pattern of climate cyclicity changed markedly at about 2.85 Ma. Earlier times were marked by high-frequency variability at the precessional frequencies or even higher frequencies, pointing to low-latitude processes as a main controlling factor driving planktonic δ 18 θ variability in this period. The high-frequency variability is not coherent with insolation and points to strong nonlinearity in the way the climate system responded to orbital forcing before the onset of large scale Northern Hemisphere glaciation. After 3 Ma, stronger 41-k.y. cyclicity appears in the record. The shift in pattern is clearest around 2.85 Ma (according to the time scale proposed by Shackleton and others in 1990), 100-200 k.y. before the most dramatic spread of Northern Hemisphere ice sheets. This indicates that high-latitude processes from this point on began to take over and influence most strongly the δ 18 θ record, which now reflects ice-volume fluctuations related to the climatic effects of obliquity forcing on the seasonality of high-latitude areas, most probably in the Northern Hemisphere. The general Pliocene trend is that high-latitude climate sensitivity and instability was increasing, and the causal factors producing the intensified glacial cyclicity during the Pliocene must be factors that enhance cooling and climate sensitivity in the subarctic areas.

The main purpose of this investigation is three dimensional modeling of currents in the Gorgan Bay using MIKE 3 Flow Model in duration summer 2010. The model is based on the numerical solution of the three-dimensional Reynolds-averaged Navier-Stokes equations, invoking the hypothesis of hydrostatic pressure in the vertical direction. Water level fluctuations in the Ashoorade station as open boundary conditions are imposed to the model as well as wind stress as a constant in space but varying in time, mean daily discharge of Qarahsoo river, evaporation, Coriolis force, bed resistance and effects of inflow and outflow of the Khozeini waterway. Horizontal diffusion is calculated using the Smagorinsky formulation and a   k turbulence model is used in the vertical. The grid cell used in computations was equal to 150×150 meters, 6 layers with vertical grid spacing 1 meter and time step interval 60 second. In this study, according to measurement data, the buoyancy effect in the Gorgan Bay has no great influence and stability factor is positive (E>0). The simulations show that the wind-induced flow creates strong currents near the coastal area and along with coastal area from west to east. Totally all the layers, the flow patterns in the Gorgan Bay are influenced by prevailing winds. Depending on the winds regime, speed and direction of the current vary in the Gorgan Bay. The bottom topography and domain geometry have an important role in forming anticlockwise circulation in the Gorgan Bay. The current velocity values in the bay are mostly affected by prevailing winds. Strong currents are also created at the Ashoradeh-Bandartorkaman mouth affected by storm surge or inter annual water level fluctuations in the Caspian Sea.

The main purpose of this investigation is three dimensional modeling of currents in the Gorgan Bay using MIKE 3 Flow Model in duration summer 2010. The model is based on the numerical solution of the three-dimensional Reynolds-averaged Navier-Stokes equations, invoking the hypothesis of hydrostatic pressure in the vertical direction. Water level fluctuations in the Ashoorade station as open boundary conditions are imposed to the model as well as wind stress as a constant in space but varying in time, mean daily discharge of Qarahsoo river, evaporation, Coriolis force, bed resistance and effects of inflow and outflow of the Khozeini waterway. Horizontal diffusion is calculated using the Smagorinsky formulation and a   k turbulence model is used in the vertical. The grid cell used in computations was equal to 150×150 meters, 6 layers with vertical grid spacing 1 meter and time step interval 60 second. In this study, according to measurement data, the buoyancy effect in the Gorgan Ba...

We investigated the behavior of the persistent current in the DNA ring in a Fishbone structure threaded by a magnetic flux , varying the electron number Ne, and the sequence size N. To this end, we use a tight-binding Hamiltonian and the Schrodinger equation. Our results show that the amplitude of the persistent current triangular oscillations increase with increasing Ne and decrease with increasing N. These factors were crucial in defining the profile of the persistent current in the DNA ring. Aspects of the saw-tooth oscillations were analyzed as a function of , revealing a range of possibilities in applications in nanotechnology.

The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect coral reef systems. For this investigation, four instrument packages were deployed across the fringing coral reef during the summer of 2001 to understand the processes governing fine-grained terrestrial sediment suspension on the shallow reef flat (h ¼ 1 m) and its advection across the reef crest and onto the deeper fore reef. The time-series measurements suggest the following conceptual model of water and fine-grained sediment transport across the reef: Relatively cool, clear water flows up onto the reef flat during flooding tides. At high tide, more deep-water wave energy is able to propagate onto the reef flat and larger Trade wind-driven waves can develop on the reef flat, thereby increasing sediment suspension. Trade wind-driven surface currents and wave breaking at the reef crest cause setup of water on the reef flat, further increasing the water depth and enhancing the development of depth-limited waves and sediment suspension. As the tide ebbs, the water and associated suspended sediment on the reef flat drains off the reef flat and is advected offshore and to the west by Trade wind-and tidally-driven currents. Observations on the fore reef show relatively high turbidity throughout the water column during the ebb tide. It therefore appears that high suspended sediment concentrations on the deeper fore reef, where active coral growth is at a maximum, are dynamically linked to processes on the muddy, shallow reef flat.

The influence of easterly and northeasterly dry and warm Santa Ana winds (SAw) on the surface circulation of Todos Santos Bay, Mexico, is studied from surface currents and wind data measured during the most extreme periods of activity (autumn-winter season). Sea surface currents were measured using a system of coastally-based HF radar stations between 2009 and 2015. Winter-mean surface circulation showed a cyclonic tendency. Atmospheric variables allowed the grouping of ~122 SAw events, 23% of which caused a noticeable change in the background circulation. Event-mean current patterns showed dissimilar responses to the acting winds, with some SAw events driving weak offshore currents, another that developed an eddy-pair circulation inside the bay, and one rather intense (winds of 8-10 ms -1 ) that developed a clockwise circulation overturning the cyclonic long-term winter-mean. In general, changes in the circulation were related to an offshore transport of surface waters into the open ocean.

High spatial resolution thermal infrared satellite images acquired 38 minutes apart from Landsat ETM+ and ASTER were used to measure the surface currents and circulation in Lake Tahoe, California‐Nevada, USA. Mean currents of 5–10 cm/s were measured, with maximum currents approaching 35 cm/s. The eastward transport of an upwelling surface jet was clearly apparent, with 15–30 cm/s currents. Three gyres were evident in the vector fields. The satellite image‐derived surface currents and circulation patterns are consistent with surface drifter measurements acquired during a different period. These results modify the findings of an earlier study using 1.1 km AVHRR imagery, which concluded there were two counter‐rotating gyres in the opposite sense to the two dominant large gyres measured in this study. The high spatial resolution and small time separation allow the surface currents and general circulation in lakes and coastal environments to be accurately quantified using the maximum cro...

The first recorded bloom of Karenia spp., resulting in brevetoxin in oysters, in the low salinity waters of the Northern Gulf of Mexico (NGOMEX) occurred in November 1996. It raised questions about the salinity tolerance of Karenia spp., previously considered unlikely to occur at salinities <24 psu, and the likelihood that the bloom would reoccur in the NGOMEX. Salinity was investigated as a factor controlling Karenia spp. abundance in the field, using data from the NGOMEX 1996 bloom and Florida coastal waters from 1954 to 2004, and growth and toxin production in cultures of Karenia brevis (Davis) G. Hansen and Moestrup. During the NGOMEX bloom, Karenia spp. occurred much more frequently at low salinities than in Florida coastal waters over the last 50 years. The data suggest that the NGOMEX bloom started on the NW Florida Shelf, an area with a higher frequency of Karenia spp. at low salinities than the rest of Florida, and was transported by an unusual westward surface current caused by Tropical Storm Josephine. The minimum salinity at which growth occurred in culture ranged between 17.5 and 20 psu, but the optimal salinity ranged between low values of 20 or 25 and high values of 37.5-45 psu, depending on the clone. The effect of salinity on toxin production in one clone of K. brevis was complex, but at all salinities brevetoxin levels were highest during the stationary growth phase, suggesting that aging, high density blooms may pose the greatest public health threat.

We study Andreev reflection in a one-dimensional square-well pair-potential. We discuss the history of the model. The current-phase relation is presented as a sum over Matsubara frequencies. How the current arises from bound and continuum levels is found by analytic continuation. We discuss two limiting cases of the square-well potential, the zero-length well and the infinite well. The model is quantitatively valid in some cases but forms the basis for understanding a wide range of problems in inhomogeneous superconductivity and superfluidity.

The well‐sampled ocean off the coast of New Jersey provides a data‐rich environment in which to study ocean current variability over the inner shelf. Using a year‐long HF radar data set, complemented with in situ and meteorological observations, the annual‐ and seasonal‐scale variabilities are examined. The hydrographic variability of the inner shelf off New Jersey is largely bimodal between summer stratification and winter mixing. An annual oceanographic and atmospheric data set was separated into these two regimes. The influence of stratification is evident through a relatively steady current response strongly correlated with the wind during the stratified season and a more variable response less correlated with the wind during the mixed season. When the water column is mixed, the influence of the local topography on the surface current variability is dependent on the slope, with a tendency for the variability to be more aligned with steeper topography.

We report an observation of surface acceleration of fast electrons in intense laser-plasma interactions. When a preformed plasma is presented in front of a solid target with a higher laser intensity, the emission direction of fast electrons is changed to the target surface direction from the laser and specular directions. This feature could be caused by the formation of a strong static magnetic field along the target surface which traps and holds fast electrons on the surface. In our experiment, the increase in the laser intensity due to relativistic self-focusing in plasma plays an important role for the formation. The strength of the magnetic field is calculated from the bent angle of the electrons, resulting in tens of percent of laser magnetic field, which agrees well with a two-dimensional particle-in-cell calculation. The strong surface current explains the high conversion efficiency on the cone-guided fast ignitor experiments.

Ocean eddies and fronts affect surface stress via two mechanisms: (1) ocean surface currents altering the relative motion between air and sea and, hence, the stress fields and (2) ocean sea surface temperature (SST) gradients forcing changes in stability and nearsurface winds. In this paper, we quantify the first effect and how it impacts Tropical Instability Waves (TIW) in the eastern Pacific. High-resolution satellite data and a regional coupled model are used to distinguish between stress changes due to the surface currents and those due to the changes in stability and near-surface winds. It is found that both mechanisms affect the surface stress curl, but they do so at different latitudes, allowing for their effect on Ekman pumping to be distinguished. The Ekman pumping due to the surface current effect alone, leads to significant damping of the TIWs. In terms of the eddy kinetic energy, the inclusion of surface current in the stress leads to decay with an e-folding time comparable with the period of the TIWs. It is, thus, an important damping mechanism to be included in ocean and coupled ocean-atmosphere models.

The ADRICOSM project was launched in October 2001, and ended in March 2005, with the main objective of demonstrating the feasibility of a near real time operational marine monitoring and forecasting system at the shelf and coastal scales, with connections to river basin runoff and coastal town sewer systems. The basic system consisted of an efficient network for the collection of marine data such as in situ temperature and salinity profiles and satellite sea surface temperature, a regional (AREG) and shelf scale modeling system, a data assimilation system and finally a coastal scale modeling system. Every week AREG releases 7 day marine forecasts at 5 km horizontal scales, which are used to nest other hydrodynamic models toward the coastal scale. Two shelf models (ASHELF-1 and ASHELF-2) at a 1.5 km horizontal scale were nested in AREG in order to simulate (and in the future to forecast) shelf scale oceanographic features. Another important aspect of ADRICOSM was the integration of t...

The ADRICOSM project was launched in October 2001, and ended in March 2005, with the main objective of demonstrating the feasibility of a near real time operational marine monitoring and forecasting system at the shelf and coastal scales, with connections to river basin runoff and coastal town sewer systems. The basic system consisted of an efficient network for the collection of marine data such as in situ temperature and salinity profiles and satellite sea surface temperature, a regional (AREG) and shelf scale modeling system, a data assimilation system and finally a coastal scale modeling system. Every week AREG releases 7 day marine forecasts at 5 km horizontal scales, which are used to nest other hydrodynamic models toward the coastal scale. Two shelf models (ASHELF-1 and ASHELF-2) at a 1.5 km horizontal scale were nested in AREG in order to simulate (and in the future to forecast) shelf scale oceanographic features. Another important aspect of ADRICOSM was the integration of the Cetina river (Croatia) and urban sewage monitoring/ modeling (Split, Croatia) systems with the shelf marine model. This integrated model system was used to simulate the dispersion of sewer discharges from the urban area in the coastal waters for water management performance studies. ADRICOSM is one of the first integrated land and marine waters operational oceanographic systems able to meet the urgent needs for reliable integrated coastal forecasts for the effective management of marine areas.

Monthly distributions of surface latent heat flux and solar irradiance in the tropical Pacific were computed from observations of the Scanning Multichannel Microwave Radiometer on Nimbus-7 and the Visible Infrared Spin Scan Radiometer on GOES-W. They are the dominant variable components of the surface heat flux, the sum of which gives the approximate thermal forcing on the ocean.

A dual-station high-frequency Wellen Radar (WERA), transmitting at 16.045 MHz, was deployed along the west Florida shelf in phased array mode during the summer of 2003. A 33-day, continuous time series of radial and vector surface current fields was acquired starting on 23 August ending 25 September 2003. Over a 30-min sample interval, WERA mapped coastal ocean currents over an ≈40 km × 80 km footprint with a 1.2-km horizontal resolution. A total of 1628 snapshots of the vector surface currents was acquired, with only 70 samples (4.3%) missing from the vector time series. Comparisons to subsurface measurements from two moored acoustic Doppler current profilers revealed RMS differences of 1 to 5 cm s−1 for both radial and Cartesian current components. Regression analyses indicated slopes close to unity with small biases between surface and subsurface measurements at 4-m depth in the east–west (u) and north–south (υ) components, respectively. Vector correlation coefficients were 0.9 w...

This paper deals with the problem of HF surface wave radar. The goal is to integrate in a unique tool the antenna radiation and the propagation calculations in order to make the analysis consistent. Only the antenna problem is presented here. However the way the propagation problem will be further considered is presented. Cross check of the tool validity and robustness were insured by developing concurrently several techniques, mixing measurements and theoretical techniques. I.

show that the new derived excitation method is indeed accurate, and can be used for the prediction of the backside radiation and side lobe levels of real life finite ground plane printed antennas. Keywords.-Integral equation, excitation models, finite ground plane, backside radiation, printed antennas.

This study investigates the potential of benzalkonium chloride (BC), a cationic surfactant, on the prevention of biofilm formation on stainless steel ASI 316 and silicone rubber, two distinct surfaces currently used on food processing facilities. The surfaces were preconditioned with several concentration of BC for 30 min. Treated surfaces were characterized by the sessile drop method, demonstrating that surfactant pre-treatment increased the hydrophobicity of the surfaces, this increase being a function of BC concentration increase applied for preconditioning. In order to ascertain the preventive effect in biofilm formation, the treated surfaces where inserted in a chemostat continuously inoculated with P. fluorescens in the exponential phase of growth, being the biofilm allowed to grow for 6 days. The results showed that BC preconditioning did not prevent or impair biofilm formation. In fact, biofilms developed on the treated surfaces presented higher biomass and respiratory activity than the ones formed on the untreated surfaces, this phenomenon being more evident for silicone than for stainless steel and for surfaces treated with higher BC concentrations. Scanning electron microscopy and biochemical analysis reveal that the difference of surface type and surface preconditioning, by itself, gave rise to the formation of structural and biochemical distinct biofilms. The overall results suggest that preconditioning of stainless steel and silicone rubber surfaces with BC allowed the formation of biofilms with more recalcitrant properties than the ones found on untreated surfaces.

An improved Iterative Physical Optics (IPO) image approximation method has been presented to dramatically increase the accuracy of the approximation and extend its applicability to PEC surfaces with smaller radii or larger curvatures. Starting from the first-order conventional PO image approximation, the IPO image approximation method iteratively correct the surface current to compensate the deviation of the electric field boundary condition on the PEC surfaces, making use of the local plane wave approximation. Numerical validations with two popular PEC surfaces, i.e., the parabolic dish antennas and the PEC spheres, are carried out and the results show that the IPO approximation method increases the surface current accuracy by more than two orders of magnitude, compared to the conventional PO image approximation method.

Our focus is on modeling the physical aspects of the Bay in order to build a forecast and prediction system. Perturbed ensemble simulations with altered initial condition parameters (temperature, salinity) are combined with concepts from Information Theory to quantify the predictability of the OSOM forecast system. Predictability provides a theoretical estimate of the potential forecasting capabilities of the model in the form of prediction time scales and enhances readily estimable timescales such as the freshwater flushing timescale. The predictability of the OSOM model is around 10-40 days, varying by perturbation parameters and season.

The distribution of silicon in the North Pacific is controlled by the utilization of silicic acid by diatoms, a process that fractionates silicon (Si) isotopic compositions. Silicon isotope variations are presented for six water column profiles from the surface mixed layer down to the deep waters of the North Pacific Ocean. Although the observed Si isotopic variations display an apparently simple inverse relationship with dissolved nutrient concentrations, in fact they reflect mixing of surface waters undergoing active Si isotope fractionation and deep-waters with more uniform concentrations and isotope compositions. Samples from the surface of the subtropical gyre have the lowest dissolved Si concentrations and heaviest Si isotope compositions of marine waters measured thus far. Fractionation in the surface waters follows a typical Rayleigh-type distillation curve for a 'closed' surface water reservoir resulting from stratification of the surface layer in the subarctic region. In contrast, an 'open' system prevails within the subtropical gyre where there is significant recycling of silicic acid in the upper water column and lateral transport of silicon within surface currents. For deep waters, the Si isotope composition distinguishes between the northern North Pacific Deep Water (NPDW) and the southerly-derived bottom water. The relatively light Si isotope compositions measured from waters within the subarctic gyre provides evidence for isolation of the nutrient pool in the North Pacific.

HF radars have been installed in many coastal sites around the world to monitor ocean parameters between the coast and maximum of about 250 km offshore. The main product of phased array radars is gridded maps of surface currents, wave heights and wind directions. Maps of surface currents (see Figure 1) can be produced every 10 – 20 minutes which, in real-time, improve navigation safety in restricted areas commonly found near ports and harbours. The time-sequence of surface current maps enables Langrangian tracking of small parcels of surface water. This analysis of the data is being used for hazard mitigation in managing suspended sediments in dredging, in emergency situations where flotsam and other drifting items need to be found, and in pollution control. Additionally the surface current measurement capability is used to assist tsunami warnings. The newly launched Tsunami Warning Center in Oman includes a network of phased-array HF radars to provide real-time tsunami monitoring. ...

Coral bleaching is an ecological response to stressful physical conditions observed to occur when strong insolation coupled with stratification of the water column leads to anomalous warming of the surface water. Stratfication requires calm winds, the absence of waves, and an absence of currents: conditions which result in limited mixing of the water column and thus confine heat due to insolation at the ocean surface. There is a strong need to identify which of the physical parameters are more significant at any given time and, more importantly, to monitor the physical parameters in near realtime to serve as a tool for long-term planning and management for marine parks and coastal waters. This paper reviews the contribution that currents make to mixing in the water column through the dissipation of turbulent kinetic energy and takes a further step to evaluate the use of surface current data to provide an index of vertical mixing. In this work, when the surface current speed is greater than a critical value, the water column is found to be vertically mixed even in the absence of wind or waves. A phased array HF Ocean Radar deployed in the southern part of the Great Barrier Reef provides a map of surface currents with high spatial resolution (4km) every 10 minutes over the grid. These surface currents are used to predict vertical stratification and mixing which can then be used as an indication for conditions under which bleaching might occur.

Based on geomorphological mapping, petrography, paleontology and luminescence data (OSL), suggest rapid climate and sea-level changes during the peak of MIS 5. Tropical fauna is present during the first part of this interstadial when oceanographic and climate conditions favoured oolite generation.

This paper revisits the calculation of the transmission line impedance for a wire above a ground plane, critically examining the traditional mirror method. In a previous study titled "A New Horizon: Rethinking Transmission Line Impedance in Electromagnetic Theory" [1], it was demonstrated that the mirror method systematically overestimates the characteristic impedance by approximately 42 Ω compared to the flux method when assuming an infinite ground plane. The flux method, based on fundamental electromagnetic principles, accounts for the coupled magnetic flux between the wire and the plane, providing a more accurate calculation. However, despite the theoretical prediction of a significant impedance difference, experimental validation has consistently failed to observe this discrepancy. This paper addresses the apparent contradiction by investigating the effect of finite ground plane width on the characteristic impedance. The analysis shows that when the ground plane width decreases, the characteristic impedance calculated by the flux method increases. For specific finite plane widths, the impedance calculated by both methods even becomes equal. These findings explain why practical measurements do not reveal the predicted discrepancy, as real-world ground planes are always finite in width. By establishing a clear relationship between ground plane width and calculated impedance, this paper advocates for the flux method as a physically consistent and reliable approach, especially in practical situations.

We discuss the scattering of acoustic or electromagnetic waves from one dimensional rough surfaces. We restrict the discussion in this report to perfectly reflecting Dirichlet surfaces (TE-polarization). The theoretical development is for both infinite surfaces and periodic surfaces, the latter equations derived from the former. We include both derivations for completeness of notation. Several theoretical developments are presented. They are characterized by integral equation solutions for the surface current or normal derivative of the total field. All the equations are discretized to a matrix system and further characterized by the sampling of the rows and columns of the matrix which is accomplished in either coordinate space (C) or spectral space (S). The standard equations are referred to here as CC equations of either first kind (CC1) or second kind (CC2). Mixed representation equations or SC type are solved as well as SS equations fully in spectral space. Computational results are presented for scattering from various periodic surfaces. The results include examples with grazing incidence, a very rough surface and a highly oscillatory surface. The examples vary over a parameter set which includes the geometrical optics regime, physical optics or resonance regime, and a renormalization regime. The objective of this study was to determine the best computational method for these problems. Briefly, the SC method was the fastest but did not converge for large slopes or very rough surfaces for reasons we explain. The SS method was slower and had the same convergence difficulties as SC. The CC methods were extremely slow but always converged. The simplest approach is to try the SC method first. Convergence, when the method works, is very fast. If convergence doesn't occur then try SS and finally CC.

The Finite Volume Time-Domain (FVTD) method finds limited application in the simulation of electromagnetic scattering from electrically large scatterers because of the fine discretization required in terms of points-per-wavelength. An efficient implementation of a higher-order FVTD method is proposed for electrically large, perfectly conducting scatterers. Higher-order and fine-grid accuracy are preserved, despite using only a first-order spatial accuracy and a coarse grid in substantial parts of the FVTD computational domain, by partially incorporating a time-domain Physical Optics (PO) approximation for the surface current. This can result in considerable savings in computational time while analyzing geometries containing electrically large, smooth sections using the FVTD method. The higher-order FVTD method in the present work is based on an Essentially Non-Oscillatory (ENO) reconstruction and results are presented for two-dimensional perfectly conducting scatterers subject to Transverse Magnetic (TM) or Transverse Electric (TE) illumination.

Nonhydrostatic mesoscale model MM5 was used in order to model a spatial distribution of bura wind in Maslenica bridge region (Croatia). A 3 km domain and a 1 km domain nested in a 3 km horizontal domain were used. Both runs were initialized from the same NWP ALADIN/Hr runs. Spatial differences between the model setups are addresed. The main characteristics of wind field was well indicated on both domains. It is found that 1 km domain much better reproduces local characteristics of wind field than 3 km domain.

Surface velocity observations from satellite tracked drifters made between 1987 and 2008 were used to resolve the surface circulation of the western Coral Sea, west of 158°E, and the Great Barrier Reef (GBR). The mean surface current map depicts well the major circulation patterns of the region, such as the position of the north Vanuatu and north Caledonia jets (NVJ and NCJ) and the western boundary currents. The North Queensland Current (NQC) and the East Australian Current (EAC) are well defined, flowing at speeds greater than 50 cm s -1 to the north, south of 15°S and 19°S, respectively. The NQC/EAC is mainly formed by the NVJ/NCJ flows, respectively. The presence of the Queensland Plateau greatly affects the westward flow, causing a zone of weak and highly variable currents that extends from 15°S to 18°S between the Queensland Plateau and the GBR shelf. Of the 235 drifters that crossed the western Coral Sea, 75 entered the GBR. Analysis of the drifter trajectories inside the GBR reveals the presence of a northwestward circulation at speeds of 22 cm s -1 north of 18°S and 0.5 cm s -1 south of 18°S. Drifter travel times used to evaluate the water residence times within the GBR indicate residence times of a few weeks for most of the lagoon.

Frequency radar is an operational oceanographic tool. Researchers have identified the basic sources of error associated with this technology. Further research evaluating errors relating to the HF radar system and corresponding algorithms can facilitate coastal environment data assimilation. Uncertainty due to two sources of error is studied to obtain a more complete accuracy of the HF radar-measured total surface current velocity vectors. The error sources include geometry of the two station HF radar system and limits of the deep-water wave assumption of the algorithm that calculates current velocity from the HF radar signal. The latter is of particular interest to our work in a shallow environment such as Corpus Christi Bay. Water depths in portions of this and other Texas bays will push the limits of the deep-water assumption for the wavelengths of interest. A map of Corpus Christi Bay illustrating quantified GDOP for each point on the radar grid and an applicable matrix transformation that accounts for error due to the deep water wave assumption. The deep water assumption error is quantified and shown to be minimal for depths as shallow as one meter.