Lagrangian flow patterns north of Cape Hatteras using near-surface drifters

Hurricane Matthew (2016) caused significant beach and dune erosion from Cape Hatteras, North Carolina, USA, to Cape Canaveral, Florida, USA. At Myrtle Beach, South Carolina, the storm caused beach recession, and much of the southern half of the city’s beaches appeared to be overwashed in post-storm surveys. Around half of the city’s beaches appeared overwashed following the storm; however, the Storm Impact Scale (SIS; Sallenger 2000) applied to a pre-storm elevation model suggests less than 10% of the city’s beaches should have experienced overwash. Spatial analysis of elevation and land cover data reveals dunes that were “overwashed” during Matthew drain from watersheds that are >35% impervious, where those showing only dune recession are <5% impervious. The densely developed downtown of Myrtle Beach sits on a low seaward-sloping terrace. Additionally, indurated strata beneath the downtown area can prevent groundwater from draining during excessive rain events. As a result, the most continuous impervious surface cover and near-surface strata lie within a half-kilometer of the beach and drain directly to the backshore. Along the U.S. Southeast coast, this is somewhat rare; many coastal systems feature a lagoon or low-lying bottomland along their landward border, which facilitates drainage of upland impervious surfaces following storm passage. At Myrtle Beach, all of the stormwater runoff is drained directly to the beach through a series of outfall pipes. Many of the outfall pipes are located along the backshore, near the elevation of storm surge during Matthew. Runoff from Matthew’s heavy rains was observed causing ponding on the landward side of the foredune and scouring around beach access walkways. Based on these observations, the severe dune erosion experienced near downtown Myrtle Beach during Hurricane Matthew may have been caused by runoff and/or groundwater flux rather than overwash. These results highlight an unexpected relationship between upland conditions and dune erosion on a developed shoreline. That is, dune erosion can be caused by mechanisms beside overwash during storm events.

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Lagrangian study of surface transport in the Kuroshio Extension area based on simulation of propagation of Fukushima-derived radionuclides

Nonlinear Processes in Geophysics ◽

10.5194/npg-21-279-2014 ◽

2014 ◽

Vol 21 (1) ◽

pp. 279-289 ◽

Cited By ~ 19

Author(s):

S. V. Prants ◽

M. V. Budyansky ◽

M. Yu. Uleysky

Keyword(s):

Nuclear Power ◽

Large Scale ◽

Kuroshio Extension ◽

Northwest Pacific ◽

Large Area ◽

Near Surface ◽

Lagrangian Tracers ◽

Surface Drifters ◽

Lagrangian Study ◽

The Kuroshio

Abstract. Lagrangian approach is applied to study near-surface large-scale transport in the Kuroshio Extension area using a simulation with synthetic particles advected by AVISO altimetric velocity field. A material line technique is proposed and applied to find out the origin of water masses in cold-core cyclonic rings pinched off from the jet in summer 2011. Tracking and Lagrangian maps provide the evidence of cross-jet transport. Fukushima-derived caesium isotopes are used as Lagrangian tracers to study transport and mixing in the area a few months after the 11 March 2011 tsunami that caused heavy damage of the Fukushima Nuclear Power Plant (FNPP). Tracking maps are computed to trace the origin of water parcels with measured levels of 134Cs and 137Cs concentrations collected during two research vessel (R/V) cruises in June and July 2011 in the large area of the northwest Pacific (Kaeriyama et al., 2013; Buesseler et al., 2012). It is shown that Lagrangian simulations are useful for finding the surface areas that are potentially dangerous due to the risk of radioactive contamination. The results of simulation are supported by tracks of the surface drifters that were deployed in the area.

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LAGRANGIAN MEASUREMENTS OF TURBULENT DISSIPATION OVER A SHALLOW TIDAL FLAT FROM PULSE COHERENT ACOUSTIC DOPPLER PROFILERS

Coastal Engineering Proceedings ◽

10.9753/icce.v33.currents.49 ◽

2012 ◽

Vol 1 (33) ◽

pp. 49 ◽

Cited By ~ 1

Author(s):

Julia C Mullarney ◽

Stephen M Henderson

Keyword(s):

High Resolution ◽

Tidal Flat ◽

Order Structure ◽

Measured Velocity ◽

Near Surface ◽

Turbulent Dissipation ◽

Dissipation Rates ◽

Surface Drifters ◽

Freshwater Plume ◽

Lagrangian Measurements

We present high resolution (25 mm spatial, 8 Hz temporal) profiles of velocity measured over a shallow tidal flat using pulse-coherent Acoustic Doppler Profilers mounted on surface drifters. The use of Lagrangian measurements mitigated the problem of resolving velocity ambiguities, a problem which often limits the application of high-resolution pulse-coherent profilers. Turbulent dissipation rates were estimated from second-order structure functions of measured velocity. Drifters were advected towards, and subsequently trapped on, a convergent surface front which marked the edge of a freshwater plume. Measured dissipation rates increased as a drifter deployed within the plume approached the front. A drifter then propagated with and along the front as the fresh plume spread across the tidal flats. Near-surface turbulent dissipation measured at the front roughly matched a theoretical mean-shear-cubed relationship, whereas dissipation measured in the stratified plume behind the front was suppressed. After removal of estimates affected by surface waves, near-bed dissipation matched the velocity cubed relationship, although scatter was substantial. Dissipation rates appeared to be enhanced when the drifter propagated across small subtidal channels.

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NEAR SURFACE FLOW PATTERNS OF TWO RECTANGULAR CYLINDERS AT A LOW REYNOLDS NUMBER

Journal of Flow Visualization and Image Processing ◽

10.1615/jflowvisimageproc.v14.i4.10 ◽

2007 ◽

Vol 14 (4) ◽

pp. 339-354

Author(s):

Jung-Hua Chou ◽

S. B. Chiu ◽

M. D. Lin

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Flow Patterns ◽

Surface Flow ◽

Near Surface ◽

Low Reynolds ◽

Rectangular Cylinders

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Wintertime shoreward near-surface currents south of Cape Hatteras

Journal of Geophysical Research Atmospheres ◽

10.1029/2001jc001193 ◽

2002 ◽

Vol 107 (C11) ◽

Cited By ~ 11

Author(s):

Dana K. Savidge

Keyword(s):

Surface Currents ◽

Near Surface ◽

Cape Hatteras

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High-Resolution Observations in the Western Mediterranean Sea: The REP14-MED Experiment

10.5194/os-2016-82 ◽

2016 ◽

Cited By ~ 2

Author(s):

Reiner Onken ◽

Heinz-Volker Fiekas ◽

Laurent Beguery ◽

Ines Borrione ◽

Andreas Funk ◽

...

Keyword(s):

Time Series ◽

High Resolution ◽

Mediterranean Sea ◽

Western Mediterranean ◽

Data Set ◽

Western Mediterranean Sea ◽

Huge Data ◽

Operational Forecasting ◽

Surface Drifters ◽

Lagrangian Flow

Abstract. The observational part of the REP14-MED experiment was conducted in June 2014 in the Sardo-Balearic Sea west of Sardinia Island (Western Mediterranean Sea). Two research vessels collected high-resolution oceanographic data by means of hydrographic casts, towed systems, and underway measurements. In addition, a vast amount of data was provided by a fleet of 11 gliders, time series were available from moored instruments, and information on Lagrangian flow patterns were obtained from surface drifters and one profiling float. The spatial resolution of the observations encompasses a spectrum over four orders of magnitude from O(101 m) to O(105 m), and the time series from the moored instruments cover a spectral range of five orders from O(101 s) to O(106 s). The objective of this article is to provide an overview of the huge data set which is utilized by various ongoing studies, focusing on (i) sub-mesoscale and mesoscale pattern analyses, (ii) operational forecasting in terms of the development and assessment of sampling strategies, assimilation methods, and model validation, (iii) modeling the variability of the ocean, and (iv) testing of new payloads for gliders.

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High-resolution observations in the western Mediterranean Sea: the REP14-MED experiment

Ocean Science ◽

10.5194/os-14-321-2018 ◽

2018 ◽

Vol 14 (2) ◽

pp. 321-335 ◽

Cited By ~ 9

Author(s):

Reiner Onken ◽

Heinz-Volker Fiekas ◽

Laurent Beguery ◽

Ines Borrione ◽

Andreas Funk ◽

...

Keyword(s):

Time Series ◽

High Resolution ◽

Mediterranean Sea ◽

Western Mediterranean ◽

Data Set ◽

Western Mediterranean Sea ◽

Huge Data ◽

Operational Forecasting ◽

Surface Drifters ◽

Lagrangian Flow

Abstract. The observational part of the REP14-MED experiment was conducted in June 2014 in the Sardo-Balearic Basin west of Sardinia (western Mediterranean Sea). Two research vessels collected high-resolution oceanographic data by means of hydrographic casts, towed systems, and underway measurements. In addition, a vast amount of data was provided by a fleet of 11 ocean gliders, time series were available from moored instruments, and information on Lagrangian flow patterns was obtained from surface drifters and one profiling float. The spatial resolution of the observations encompasses a spectrum over 4 orders of magnitude from 𝒪(101 m) to 𝒪(105 m), and the time series from the moored instruments cover a spectral range of 5 orders from 𝒪(101 s) to 𝒪(106 s). The objective of this article is to provide an overview of the huge data set which has been utilised by various studies, focusing on (i) water masses and circulation, (ii) operational forecasting, (iii) data assimilation, (iv) variability of the ocean, and (v) new payloads for gliders.

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Properties and evolution of a submesoscale cyclonic spiral

10.5194/os-2021-86 ◽

2021 ◽

Author(s):

Reiner Onken ◽

Burkard Baschek

Keyword(s):

Extreme Values ◽

Euphotic Zone ◽

Horizontal Resolution ◽

Surface Flow ◽

Ocean Modeling ◽

Vortex Center ◽

Regional Ocean Modeling System ◽

Near Surface ◽

Surface Drifters ◽

Radial Outflow

Abstract. The evolution of a submesoscale cyclonic spiral of 1 km in diameter is simulated with ROMS (Regional Ocean Modeling System) using 33.3 m horizontal resolution in a triple-nested configuration. The generation of the spiral starts from a dense filament that is rolled into a vortex and detaches from the filament. During spin-up, extreme values are attained by various quantities, that are organized in single-arm and multi-arm spirals. The spin-down starts when the cyclone separates from the filament. At the same time, the horizontal speed develops a dipole-like pattern and isotachs form closed contours around the vortex center. The amplitudes of most quantities decrease significantly, but the instantaneous vertical velocity w exhibits high-frequency oscillations and more pronounced extremes than during spin-up. The oscillations are due to vortex Rossby waves (VRWs), that circle the eddy counterclockwise and generate multi-arm spirals with alternating signs by means of azimuthal vorticity advection. Experiments with virtual surface drifters and isopycnal floats indicate downwelling everywhere near the surface. The downwelling is most intense in the center of the spiral at all depth levels, leading to a radial outflow in the thermocline and weak upwelling at the periphery. This overturning circulation is driven by convergent near-surface flow and associated subduction of isopycnals. While the downwelling in the center may support the export of particulate organic carbon from the mixed layer into the main thermocline, the upwelling at the periphery effectuates an upward isopycnal transport of nutrients, enhancing the growth of phytoplankton in the euphotic zone.

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Eulerian and Lagrangian Correspondence of High-Frequency Radar and Surface Drifter Data: Effects of Radar Resolution and Flow Components

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-13-00146.1 ◽

2014 ◽

Vol 31 (4) ◽

pp. 945-966 ◽

Cited By ~ 24

Author(s):

I. I. Rypina ◽

A. R. Kirincich ◽

R. Limeburner ◽

I. A. Udovydchenkov

Keyword(s):

High Frequency ◽

Surface Current ◽

Near Surface ◽

Residual Currents ◽

Smoothing Effects ◽

Temporal Averaging ◽

Temporal And Spatial ◽

Radar Resolution ◽

Surface Drifters ◽

Flow Components

Abstract This study investigated the correspondence between the near-surface drifters from a mass drifter deployment near Martha’s Vineyard, Massachusetts, and the surface current observations from a network of three high-resolution, high-frequency radars to understand the effects of the radar temporal and spatial resolution on the resulting Eulerian current velocities and Lagrangian trajectories and their predictability. The radar-based surface currents were found to be unbiased in direction but biased in magnitude with respect to drifter velocities. The radar systematically underestimated velocities by approximately 2 cm s−1 due to the smoothing effects of spatial and temporal averaging. The radar accuracy, quantified by the domain-averaged rms difference between instantaneous radar and drifter velocities, was found to be about 3.8 cm s−1. A Lagrangian comparison between the real and simulated drifters resulted in the separation distances of roughly 1 km over the course of 10 h, or an equivalent separation speed of approximately 2.8 cm s−1. The effects of the temporal and spatial radar resolution were examined by degrading the radar fields to coarser resolutions, revealing the existence of critical scales (1.5–2 km and 3 h) beyond which the ability of the radar to reproduce drifter trajectories decreased more rapidly. Finally, the importance of the different flow components present during the experiment—mean, tidal, locally wind-driven currents, and the residual velocities—was analyzed, finding that, during the study period, a combination of tidal, locally wind-driven, and mean currents were insufficient to reliably reproduce, with minimal degradation, the trajectories of real drifters. Instead, a minimum combination of the tidal and residual currents was required.

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