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

2014 ◽  
Vol 31 (4) ◽  
pp. 945-966 ◽  
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.

ИССЛЕДОВАНИЯ АКУСТИЧЕСКИХ ХАРАКТЕРИСТИК ВЕРХНЕГО СЛОЯ МОРЯ МЕТОДОМ МНОГОЧАСТОТНОГО АКУСТИЧЕСКОГО ЗОНДИРОВАНИЯ

2020 ◽  
Author(s):  
V.A. Bulanov ◽  
I.V. Korskov ◽  
A.V. Storozhenko ◽  
S.N. Sosedko
Keyword(s):  
High Frequency ◽  
Wave Motion ◽  
High Spatial Resolution ◽  
Wind Waves ◽  
Acoustic Parameter ◽  
Sea Surface ◽  
Near Surface ◽  
Acoustical Properties ◽  
Acoustic Spectroscopy ◽  
Sea Bottom

Описано применение акустического зондирования для исследования акустических характеристик верхнего слоя моря с использованием широкополосных остронаправленных инвертированных излучателей,устанавливаемых на дно. В основу метода положен принцип регистрации обратного рассеяния и отраженияот поверхности моря акустических импульсов с различной частотой, позволяющий одновременно измерятьрассеяние и поглощение звука и нелинейный акустический параметр морской воды. Многочастотное зондирование позволяет реализовать акустическую спектроскопию пузырьков в приповерхностных слоях моря,проводить оценку газосодержания и получать данные о спектре поверхностного волнения при различных состояниях моря вплоть до штормовых. Применение остронаправленных высокочастотных пучков ультразвукапозволяет разделить информацию о планктоне и пузырьках и определить с высоким пространственным разрешением структуру пузырьковых облаков, образующихся при обрушении ветровых волн, и структуру планктонных сообществ. Участие планктона в волновом движении в толще морской воды позволяет определитьпараметры внутренних волн спектр и распределение по амплитудам в различное время.This paper represents the application of acoustic probingfor the investigation of acoustical properties of the upperlayer of the sea using broadband narrow-beam invertedtransducers that are mounted on the sea bottom. Thismethod is based on the principle of the recording of thebackscattering and reflections of acoustic pulses of differentfrequencies from the sea surface. That simultaneouslyallows measuring scattering and absorption of the soundand non-linear acoustic parameter of seawater. Multifrequencyprobing allows performing acoustic spectroscopy ofbubbles in the near-surface layer of the sea, estimating gascontent, and obtaining data on the spectrum of the surfacewaves in various states of the sea up to a storm. Utilizationof the high-frequency narrow ultrasound beams allows us toseparate the information about plankton and bubbles and todetermine the structure of bubble clouds, created during thebreaking of wind waves, along with the structure of planktoncommunities with high spatial resolution. The participationof plankton in the wave motion in the seawater columnallows determining parameters of internal waves, such asspectrum and distribution of amplitudes at different times.

The Integrated Ocean Observing System High-Frequency Radar Network: Status and Local, Regional, and National Applications

2010 ◽  
Vol 44 (6) ◽  
pp. 122-132 ◽  
Author(s):  
Jack Harlan ◽  
Eric Terrill ◽  
Lisa Hazard ◽  
Carolyn Keen ◽  
Donald Barrick ◽  
...  
Keyword(s):  
High Frequency ◽  
Surface Current ◽  
Water Quality Monitoring ◽  
Velocity Fields ◽  
Common Source ◽  
Integrated Network ◽  
High Frequency Radar ◽  
Radar Network ◽  
Network Status ◽  
Ocean Observing

AbstractA national high-frequency radar network has been created over the past 20 years or so that provides hourly 2-D ocean surface current velocity fields in near real time from a few kilometers offshore out to approximately 200 km. This preoperational network is made up of more than 100 radars from 30 different institutions. The Integrated Ocean Observing System efforts have supported the standards-based ingest and delivery of these velocity fields to a number of applications such as coastal search and rescue, oil spill response, water quality monitoring, and safe and efficient marine navigation. Thus, regardless of the operating institution or location of the radar systems, emergency response managers, and other users, can rely on a common source and means of obtaining and using the data. Details of the history, the physics, and the application of high-frequency radar are discussed with successes of the integrated network highlighted.

scholarly journals Interannual response of global ocean hindcasts to a satellite-based correction of precipitation fluxes

2012 ◽  
Vol 9 (2) ◽  
pp. 611-648 ◽  
Author(s):  
A. Storto ◽  
I. Russo ◽  
S. Masina
Keyword(s):  
Ocean Circulation ◽  
Surface Current ◽  
Global Ocean ◽  
Surface Salinity ◽  
Near Surface ◽  
Convergence Zones ◽  
Circumpolar Current ◽  
The Tropics ◽  
Spatially Varying ◽  
The Antarctic

Abstract. We present a methodology to correct precipitation fluxes from the ECMWF atmospheric reanalysis (ERA-Interim) for oceanographic applications. The correction is performed by means of a spatially varying monthly climatological coefficient, computed within the period 1989–2008 by comparison between ERA-Interim and a satellite-based passive microwave precipitation product. ERA-Interim exhibits a systematic over-estimation of precipitation within the inter-tropical convergence zones (up to 3 mm d−1) and under-estimation at mid- and high- latitudes (up to −4 mm d−1). The correction has been validated within eddy-permitting resolution global ocean hindcasts (1989–2009), demonstrating the ability of our strategy in attenuating the 20-yr mean global EMP negative imbalance by 16%, reducing the near-surface salinity fresh bias in the Tropics up to 1 psu and improving the representation of the sea level interannual variability, with an SSH error decrease of 8%. The ocean circulation is also proved to benefit from the correction, especially in correspondence of the Antarctic Circumpolar Current, where the error in the near-surface current speed decreases by a 9%. Finally, we show that the correction leads to volume and freshwater transports that better agree with independent estimates.

scholarly journals Evaluating the surface circulation in the Ebro delta (northeastern Spain) with quality-controlled high-frequency radar measurements

Ocean Science ◽  
2015 ◽  
Vol 11 (6) ◽  
pp. 921-935 ◽  
Author(s):  
P. Lorente ◽  
S. Piedracoba ◽  
J. Soto-Navarro ◽  
E. Alvarez-Fanjul
Keyword(s):  
High Frequency ◽  
Marine Protected Area ◽  
Accuracy Assessment ◽  
Surface Current ◽  
Radar Data ◽  
Western Mediterranean ◽  
Hf Radar ◽  
Ebro Delta ◽  
Ebro River ◽  
Surface Circulation

Abstract. The Ebro River delta is a relevant marine protected area in the western Mediterranean. In order to promote the conservation of its ecosystem and support operational decision making in this sensitive area, a three-site standard-range (13.5 MHz) CODAR SeaSonde high-frequency (HF) radar was deployed in December 2013. The main goal of this work is to explore basic features of the sea surface circulation in the Ebro deltaic region as derived from reliable HF radar surface current measurements. For this aim, a combined quality control methodology was applied: firstly, 1-year long (2014) real-time web monitoring of nonvelocity-based diagnostic parameters was conducted to infer both radar site status and HF radar system performance. The signal-to-noise ratio at the monopole exhibited a consistent monthly evolution, although some abrupt decreases (below 10 dB), occasionally detected in June for one of the radar sites, impacted negatively on the spatiotemporal coverage of total current vectors. It seemed to be sporadic episodes since radar site overall performance was found to be robust during 2014. Secondly, a validation of HF radar data with independent in situ observations from a moored current meter was attempted for May–October 2014. The accuracy assessment of radial and total vectors revealed a consistently high agreement. The directional accuracy of the HF radar was rated at better than 8°. The correlation coefficient and root mean square error (RMSE) values emerged in the ranges [0.58–0.83] and [4.02–18.31] cm s−1, respectively. The analysis of the monthly averaged current maps for 2014 showed that the HF radar properly represented basic oceanographic features previously reported, namely, the predominant southwestward flow, the coastal clockwise eddy confined south of the Ebro delta mouth, or the Ebro River impulsive-type freshwater discharge. The EOF analysis related the flow response to local wind forcing and confirmed that the surface current field evolved in space and time according to three significantly dominant modes of variability.

scholarly journals On the skill of high frequency precipitation analyses

2014 ◽  
Vol 11 (10) ◽  
pp. 11605-11636
Author(s):  
A. Kann ◽  
I. Meirold-Mautner ◽  
F. Schmid ◽  
G. Kirchengast ◽  
J. Fuchsberger
Keyword(s):  
High Frequency ◽  
Cross Validation ◽  
Rain Gauge ◽  
Convective Precipitation ◽  
Convective Condition ◽  
Station Network ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial ◽  
Merging Algorithms ◽  
Very High

Abstract. The ability of radar-rain gauge merging algorithms to precisely analyse convective precipitation patterns is of high interest for many applications, e.g. hydrological modelling. However, due to drawbacks of methods like cross-validation and due to the limited availability of reference datasets on high temporal and spatial scale, an adequate validation is usually hardly possible, especially on an operational basis. The present study evaluates the skill of very high resolution and frequently updated precipitation analyses (rapid-INCA) by means of a very dense station network (WegenerNet), operated in a limited domain of the south-eastern parts of Austria (Styria). Based on case studies and a longer term validation over the convective season 2011, a general underestimation of the rapid-INCA precipitation amounts is shown, although the temporal and spatial variability of the errors is – by convective nature – high. The contribution of the rain gauge measurements to the analysis skill is crucial. However, the capability of the analyses to precisely assess the convective precipitation distribution predominantly depends on the representativeness of the stations under the prevalent convective condition.

scholarly journals A Method for Processing Acoustic Doppler Current Profiler Velocity Data from Towed, Undulating Vehicles

2008 ◽  
Vol 25 (9) ◽  
pp. 1710-1716 ◽  
Author(s):  
Jiayi Pan ◽  
David A. Jay
Keyword(s):  
Surface Waters ◽  
High Frequency ◽  
Acoustic Doppler Current Profiler ◽  
Small Time ◽  
Ocean Current ◽  
Near Surface ◽  
Vertical Range ◽  
External Reference ◽  
Current Profiler ◽  
Adcp Measurements

Abstract The utility of the acoustic Doppler current profiler (ADCP) for sampling small time and space scales of coastal environments can be enhanced by mounting a high-frequency (1200 kHz) ADCP on an oscillating towed body. This approach requires both an external reference to convert the measured shears to velocities in the earth coordinates and a method to determine the towed body velocities. During the River Influence on the Shelf Ecosystems (RISE) project cruise, a high-frequency (1200 kHz) and narrowbeam ADCP with mode 12 sampling was mounted on a TRIAXUS oscillating towfish, which steers a 3D path behind the ship. This deployment approach extended the vertical range of the ADCP and allowed it to sample near-surface waters outside the ship’s wake. The measurements from a ship-mounted 1200-kHz narrowbeam ADCP are used as references for TRIAXUS ADCP data, and a method of overlapping bins is employed to recover the entire vertical range of the TRIAXUS ADCP. The TRIAXUS vehicle horizontal velocities are obtained by removing the derived ocean current velocity from the TRIAXUS ADCP measurements. The results show that the method is practical.

scholarly journals Investigations into Synoptic Spatiotemporal Characteristics of Coastal Upper Ocean Circulation Using High Frequency Radar Data and Model Output

2020 ◽  
Vol 12 (17) ◽  
pp. 2841
Author(s):  
Lei Ren ◽  
Nanyang Chu ◽  
Zhan Hu ◽  
Michael Hartnett
Keyword(s):  
Ocean Circulation ◽  
High Frequency ◽  
Numerical Models ◽  
Surface Current ◽  
Flow Fields ◽  
Surface Flow ◽  
Self Organizing Map ◽  
Eof Analysis ◽  
Surface Flows ◽  
High Frequency Radar

Numerical models and remote sensing observation systems such as radars are useful for providing information on surface flows for coastal areas. Evaluation of their performance and extracting synoptic characteristics are challenging and important tasks. This research aims to investigate synoptic characteristics of surface flow fields through undertaking a detailed analysis of model results and high frequency radar (HFR) data using self-organizing map (SOM) and empirical orthogonal function (EOF) analysis. A dataset of surface flow fields over thirteen days from these two sources was used. A SOM topology map of size 4 × 3 was developed to explore spatial patterns of surface flows. Additionally, comparisons of surface flow patterns between SOM and EOF analysis were carried out. Results illustrate that both SOM and EOF analysis methods are valuable tools for extracting characteristic surface current patterns. Comparisons indicated that the SOM technique displays synoptic characteristics of surface flow fields in a more detailed way than EOF analysis. Extracted synoptic surface current patterns are useful in a variety of applications, such as oil spill treatment and search and rescue. This research provides an approach to using powerful tools to diagnose ocean processes from different aspects. Moreover, it is of great significance to assess SOM as a potential forecasting tool for coastal surface currents.

scholarly journals Analysis of temporal and spatial variability of atmospheric CO<sub>2</sub> concentration within Paris from the GreenLITE™ laser imaging experiment

2019 ◽  
Vol 19 (22) ◽  
pp. 13809-13825 ◽  
Author(s):  
Jinghui Lian ◽  
François-Marie Bréon ◽  
Grégoire Broquet ◽  
T. Scott Zaccheo ◽  
Jeremy Dobler ◽  
...  
Keyword(s):  
Urban Canopy ◽  
Temporal Variations ◽  
Horizontal Resolution ◽  
Atmospheric Co2 ◽  
Laser Imaging ◽  
Near Surface ◽  
Co2 Concentrations ◽  
Temporal And Spatial ◽  
The City

Abstract. In 2015, the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE™) measurement system was deployed for a long-duration experiment in the center of Paris, France. The system measures near-surface atmospheric CO2 concentrations integrated along 30 horizontal chords ranging in length from 2.3 to 5.2 km and covering an area of 25 km2 over the complex urban environment. In this study, we use this observing system together with six conventional in situ point measurements and the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and two urban canopy schemes (Urban Canopy Model – UCM; Building Effect Parameterization – BEP) at a horizontal resolution of 1 km to analyze the temporal and spatial variations in CO2 concentrations within the city of Paris and its vicinity for the 1-year period spanning December 2015 to November 2016. Such an analysis aims at supporting the development of CO2 atmospheric inversion systems at the city scale. Results show that both urban canopy schemes in the WRF-Chem model are capable of reproducing the seasonal cycle and most of the synoptic variations in the atmospheric CO2 point measurements over the suburban areas as well as the general corresponding spatial differences in CO2 concentration that span the urban area. However, within the city, there are larger discrepancies between the observations and the model results with very distinct features during winter and summer. During winter, the GreenLITE™ measurements clearly demonstrate that one urban canopy scheme (BEP) provides a much better description of temporal variations and horizontal differences in CO2 concentrations than the other (UCM) does. During summer, much larger CO2 horizontal differences are indicated by the GreenLITE™ system than both the in situ measurements and the model results, with systematic east–west variations.

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