An AUV survey in the littoral zone: small-scale subsurface variability accompanying synoptic observations of surface currents

2001 ◽  
Vol 26 (4) ◽  
pp. 752-768 ◽  
Author(s):  
M.R. Dhanak ◽  
P.E. An ◽  
K. Holappa
Keyword(s):  
Littoral Zone ◽  
Small Scale ◽  
Surface Currents ◽  
Synoptic Observations

Time Evolution Of Beach Tar, Oil Slicks, And Seeps In The Coal Oil Point Seep Field, Santa Barbara Channel, California

2005 ◽  
Vol 2005 (1) ◽  
pp. 855-860 ◽  
Author(s):  
Ira Leifer ◽  
Tonya Del Sontro ◽  
Bruce Luyendyk ◽  
Kris Broderick
Keyword(s):  
Arrival Time ◽  
Small Scale ◽  
Surface Currents ◽  
Santa Barbara Channel ◽  
Santa Barbara ◽  
Variability Modeling ◽  
Oil Slick ◽  
Kelp Bed ◽  
Tar Oil ◽  
Trajectory Simulations

ABSTRACT Linking beach tar with sources in a complex natural marine seepage area presents numerous challenges. Efforts at Coal Oil Point (COP), CA included beach tar distribution surveys, oil slick tracking, sampling, and chemical analysis, underwater scuba surveys, aerial surveys, and numerical modeling. Despite a wind from the east and current to the west, a slick was tracked initially north from its source, presumably due to spreading, then it drifted east, ending in a kelp bed off COP. Sample chromatograms showed mixing with another oil slick by the appearance of a heavier series of n-alkane peaks where the trajectory changed direction. Trajectory simulations suggested that interface currents were poorly described by parameterizations of wind and surface currents, and/or the existence of small-scale circulations not resolved by CODAR or the drift buoy. Detailed tar accumulation surveys covered 175-m (4400 m2) of COP beach where tar accumulation generally is greatest. Maximum total beach tar observed was 1.5 kg, with significant variability. Modeling suggested a similar source location for the three analyzed surveys. Analysis also suggested kelp canopies can play a significant roll in the arrival time and location of beach tar by blocking onshore transport. However, wind, current, and kelp conditions were such that much of the variability in tar accumulation for these surveys probably was from source emission variability.

scholarly journals The Occurrence, Drivers, and Implications of Submesoscale Eddies on the Martha’s Vineyard Inner Shelf

2016 ◽  
Vol 46 (9) ◽  
pp. 2645-2662 ◽  
Author(s):  
Anthony Kirincich
Keyword(s):  
Relative Vorticity ◽  
Hf Radar ◽  
Small Scale ◽  
Surface Currents ◽  
Inner Shelf ◽  
Martha's Vineyard ◽  
Martha’S Vineyard ◽  
Eddy Generation ◽  
Wind Driven Currents ◽  
Eastern Edge

AbstractThe occurrence, drivers, and implications of small-scale O(2–5) km diameter coherent vortices, referred to as submesoscale eddies, over the inner shelf south of Martha’s Vineyard, Massachusetts, are examined using high-frequency (HF), radar-based, high-resolution (400 m) observations of surface currents. Within the 300 km2 study area, eddies occurred at rates of 1 and 4 day−1 in winter and summer, respectively. Most were less than 5 h in duration, smaller than 4 km in diameter, and rotated less than once over their lifespan; 60% of the eddies formed along the eastern edge of study area, adjacent to Wasque Shoal, and moved westward into the interior, often with relative vorticity greater than f. Eddy generation was linked to vortex stretching on the ebb and flood tide as well as the interaction of the spatially variable tide and the wind-driven currents; however, these features had complex patterns of surface divergence and stretching. Eddies located away from Wasque Shoal were related to the movement of wind-driven surface currents, as wind direction controlled where eddies formed as well as density effects. Using an analysis of particles advected within the radar-based surface currents, the observed eddies were found to be generally leaky, losing 60%–80% of particles over their lifespan, but still more retentive than the background flow. As a result, the combined translation and rotational effects of the observed eddies were an important source of lateral exchange for surface waters over the inner shelf.

scholarly journals A Coupled OpenFOAM-WRF Study on Atmosphere-Wake-Ocean Interaction

Fluids ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 12
Author(s):  
John Gilbert ◽  
Jonathan Pitt
Keyword(s):  
Field Data ◽  
Wrf Model ◽  
Coupled Model ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Sea Surface ◽  
Small Scale ◽  
Surface Currents ◽  
Atmospheric Component ◽  
Surface Disturbances

This work aims to better understand how small scale disturbances that are generated at the air-sea interface propagate into the surrounding atmosphere under realistic environmental conditions. To that end, a one-way coupled atmosphere-ocean model is presented, in which predictions of sea surface currents and sea surface temperatures from a microscale ocean model are used as constant boundary conditions in a larger atmospheric model. The coupled model consists of an ocean component implemented while using the open source CFD software OpenFOAM, an atmospheric component solved using the Weather Research and Forecast (WRF) model, and a Python-based utility foamToWRF, which is responsible for mapping field data between the ocean and atmospheric domains. The results are presented for two demonstration cases, which indicate that the proposed coupled model is able to capture the propagation of small scale sea surface disturbances in the atmosphere, although a more thorough study is required in order to properly validate the model.

scholarly journals Interoperability of SeaSondes and Wellen Radars in Mapping Radial Surface Currents

2013 ◽  
Vol 30 (11) ◽  
pp. 2662-2675 ◽  
Author(s):  
J. Martinez-Pedraja ◽  
L. K. Shay ◽  
B. K. Haus ◽  
C. Whelan
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Hf Radar ◽  
Small Scale ◽  
Surface Currents ◽  
Florida Current ◽  
Current Profiler ◽  
Florida Straits ◽  
Subsurface Current ◽  
Geometric Dilution Of Precision ◽  
Good Agreement

Abstract A dual-station high-frequency (HF) Wellen Radar (WERA) transmitting at 16 MHz has observed near-real-time surface currents over an approximate range of 100 km across the Florida Straits since July 2004. During a 10-day period in April 2005 (15–25 April), a pair of 12.6-MHz SeaSondes (SS) were deployed south of the WERAs sites by NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). The resulting SS grid overlapped the southern portion of the WERA domain. During the same period of time, a bottom-mounted acoustic Doppler current profiler (ADCP) acquired subsurface current measurements within these HF radar grids starting at 14 m below the surface in water of 86-m depth. The interoperability of beam-forming (WERA) and direction-finding (SS) HF radar technologies was examined. Comparisons of radial and vector currents for an 8-day concurrent time series suggested good agreement in current direction over both domains, where the surface currents' magnitudes were a maximum of 1.2 m s−1. In the core of the radar domains consisting of 108 cells, hourly vector currents were obtained by combining WERA and SS radials. Generally, this can be done in a relatively straightforward manner, considering the geometric dilution of precision (GDOP). A second key issue is downscaling the SS measurements from a 3-km grid to a 1.1-km grid to match the WERA output. This enhanced grid spacing is important along the western flank of the Florida Current, where energetic, small-scale surface features have been observed.

scholarly journals Eddy Detection in HF Radar-Derived Surface Currents in the Gulf of Naples

2019 ◽  
Vol 12 (1) ◽  
pp. 97 ◽  
Author(s):  
Leonardo Bagaglini ◽  
Pierpaolo Falco ◽  
Enrico Zambianchi
Keyword(s):  
Velocity Fields ◽  
Automated Detection ◽  
Hf Radar ◽  
Surface Currents ◽  
Tracer Transport ◽  
Gulf Of Naples ◽  
Radar Systems ◽  
Inorganic Matter ◽  
Radar Velocity ◽  
Synoptic Observations

Submesoscale eddies play an important role in the energy transfer from the mesoscale down to the dissipative range, as well as in tracer transport. They carry inorganic matter, nutrients and biomass; in addition, they may act as pollutant conveyors. However, synoptic observations of these features need high resolution sampling, in both time and space, making their identification challenging. Therefore, HF coastal radar were and are successfully used to accurately identify, track and describe them. In this paper we tested two already existing algorithms for the automated detection of submesoscale eddies. We applied these algorithms to HF radar velocity fields measured by a network of three radar systems operating in the Gulf of Naples. Both methods showed shortcomings, due to the high non-geostrophy of the observed currents. For this reason we developed a third, novel algorithm that proved to be able to detect highly asymmetrical eddies, often not properly identified by the previous ones. We used the results of the application of this algorithm to estimate the eddy boundary profiles and the eddy spatial distribution.

scholarly journals Environmental Geophysical Study of the Groundwater Mineralization in a Plot of the Cotonou Littoral Zone (South Benin)

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Yalo Nicaise ◽  
Descloitres Marc ◽  
Alassane Abdoukarim ◽  
Mama Daouda ◽  
Boukari Moussa
Keyword(s):  
Fresh Water ◽  
Water Table ◽  
Littoral Zone ◽  
Geophysical Methods ◽  
Environmental Study ◽  
Small Scale ◽  
Water Interface ◽  
Water Conductivity ◽  
Electrical Resistivities ◽  
Geophysical Study

Geophysical investigations comprising electrical resistivity and electromagnetic conductivities methods were deployed in a 350 m2sector, strewn with 11 wells. Within the framework of an environmental study on a small scale in the south of Benin, the water conductivity of these wells was measured to determine in a direct way mineralization of the coastal water table in the littoral zone. This environmental study aimed to prospect by the geophysical methods the space extension of the water table mineralization obtained by direct measurements of water conductivity in the well and the depth of the fresh water/salted water interface in the coastal aquifer. Electromagnetic measurements of conductivities made it possible to chart a gradient of mineralization in the northwest direction. The logs of vertical electric soundings showed a deepening of the fresh water/salted water interface in the southern part and its rupture in the northern part. The electrical resistivities of the interface are sensitive to the degree of its mineralization. It has been observed that the geophysical methods in electrical and electromagnetic prospection are a great contribution to the environmental study of the water table mineralization in the littoral zone for a sustainable management of the water resource.

Reasons to strike first

2019 ◽  
Vol 42 ◽  
Author(s):  
William Buckner ◽  
Luke Glowacki
Keyword(s):  
Intergroup Conflict ◽  
Small Scale

Abstract De Dreu and Gross predict that attackers will have more difficulty winning conflicts than defenders. As their analysis is presumed to capture the dynamics of decentralized conflict, we consider how their framework compares with ethnographic evidence from small-scale societies, as well as chimpanzee patterns of intergroup conflict. In these contexts, attackers have significantly more success in conflict than predicted by De Dreu and Gross's model. We discuss the possible reasons for this disparity.

Exploring Coronal Structures with SOHO

2000 ◽  
Vol 179 ◽  
pp. 403-406
Author(s):  
M. Karovska ◽  
B. Wood ◽  
J. Chen ◽  
J. Cook ◽  
R. Howard
Keyword(s):  
Solar Corona ◽  
Image Enhancement ◽  
Coronal Mass Ejections ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Low Contrast ◽  
Contrast Structures ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

Scanning tunneling microscopy and atomic force microscopy: New tools for biology

1989 ◽  
Vol 47 ◽  
pp. 778-779
Author(s):  
CE Bracker ◽  
P. K. Hansma
Keyword(s):  
Physical Property ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Small Scale ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
New Family ◽  
Small Probe ◽  
Atomic Force ◽  
Transmission Electron

A new family of scanning probe microscopes has emerged that is opening new horizons for investigating the fine structure of matter. The earliest and best known of these instruments is the scanning tunneling microscope (STM). First published in 1982, the STM earned the 1986 Nobel Prize in Physics for two of its inventors, G. Binnig and H. Rohrer. They shared the prize with E. Ruska for his work that had led to the development of the transmission electron microscope half a century earlier. It seems appropriate that the award embodied this particular blend of the old and the new because it demonstrated to the world a long overdue respect for the enormous contributions electron microscopy has made to the understanding of matter, and at the same time it signalled the dawn of a new age in microscopy. What we are seeing is a revolution in microscopy and a redefinition of the concept of a microscope.Several kinds of scanning probe microscopes now exist, and the number is increasing. What they share in common is a small probe that is scanned over the surface of a specimen and measures a physical property on a very small scale, at or near the surface. Scanning probes can measure temperature, magnetic fields, tunneling currents, voltage, force, and ion currents, among others.

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