scholarly journals Estimating Coastal Winds by Assimilating High-Frequency Radar Spectrum Data in SWAN

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7811
Author(s):  
Philip Muscarella ◽  
Kelsey Brunner ◽  
David Walker
Keyword(s):  
High Frequency ◽  
Wave Spectrum ◽  
Coastal Ocean ◽  
Ocean Model ◽  
Hf Radar ◽  
Doppler Spectrum ◽  
Observation Data ◽  
Swan Model ◽  
Wave Models ◽  
Using Data

Many activities require accurate wind and wave forecasts in the coastal ocean. The assimilation of fixed buoy observations into spectral wave models such as SWAN (Simulating Waves Nearshore) can provide improved estimates of wave forecasts fields. High-frequency (HF) radar observations provide a spatially expansive dataset in the coastal ocean for assimilation into wave models. A forward model for the HF Doppler spectrum based on first- and second-order Bragg scattering was developed to assimilate the HF radar wave observations into SWAN. This model uses the spatially varying wave spectra computed using the SWAN model, forecast currents from the Navy Coastal Ocean Model (NCOM), and system parameters from the HF radar sites to predict time-varying range-Doppler maps. Using an adjoint of the HF radar model, the error between these predictions and the corresponding HF Doppler spectrum observations can be translated into effective wave-spectrum errors for assimilation in the SWAN model for use in correcting the wind forcing in SWAN. The initial testing and validation of this system have been conducted using data from ten HF radar sites along the Southern California Bight during the CASPER-West experiment in October 2017. The improved winds compare positively to independent observation data, demonstrating that this algorithm can be utilized to fill an observational gap in the coastal ocean for winds and waves.

scholarly journals Real time assimilation of HF radar currents into a coastal ocean model

2001 ◽  
Vol 28 (3-4) ◽  
pp. 161-182 ◽  
Author(s):  
Øyvind Breivik ◽  
Øyvind Sætra
Keyword(s):  
Real Time ◽  
Coastal Ocean ◽  
Ocean Model ◽  
Hf Radar ◽  
Coastal Ocean Model

scholarly journals Validation of Surface Current Measurements in the Northern Adriatic Sea from High-Frequency Radars

2010 ◽  
Vol 27 (5) ◽  
pp. 908-919 ◽  
Author(s):  
Simone Cosoli ◽  
Andrea Mazzoldi ◽  
Miroslav Gačić
Keyword(s):  
High Frequency ◽  
Adriatic Sea ◽  
Surface Current ◽  
Broadband Noise ◽  
Radial Velocities ◽  
Hf Radar ◽  
Doppler Spectrum ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
Vector Correlation

Abstract The performances of a shore-based high-frequency (HF) radar network deployed along the coast of the Venice lagoon (northern Adriatic Sea) are discussed based on a comparison with a single bottom-mounted ADCP deployed in the shallow-water area offshore of the lagoon for a 40-day period in August–September 2005. The analyses, carried out using currents representative of the first meter for the HF radars and 2.5 m for the ADCP, gave rms differences of radial currents in the range of 8.7–14.7 cm s−1 (correlation 0.37– 0.82) for the ideal pattern and 8.4–20.5 cm s−1 (correlation 0.14–0.84) for the measured pattern. Good correlation was found between surface current vectors and moored data (scalar correlation up to R = 0.83, vector correlation ρ = 0.78, veering angle 6°). Comparison metrics were improved for the low-passed currents. Angular offsets ranged between +6° and +11°. Differences depended primarily on the geophysical variability within the water column. Bearing offsets also contributed because they lead to comparisons with radial velocities at erroneous angular sectors. Radar performances were severely affected by strong northeasterly wind pulses in their early stages. An increased broadband noise, spread over the entire Doppler spectrum across all ranges to the antennas, masked the Bragg peaks and determined the loss in radar coverage, introducing gross underestimations of both radial velocities and total currents.

Variational assimilation of HF radar surface currents in a coastal ocean model off Oregon

2012 ◽  
Vol 49-50 ◽  
pp. 86-104 ◽  
Author(s):  
Peng Yu ◽  
Alexander L. Kurapov ◽  
Gary D. Egbert ◽  
John S. Allen ◽  
P. Michael Kosro
Keyword(s):  
Coastal Ocean ◽  
Ocean Model ◽  
Hf Radar ◽  
Surface Currents ◽  
Variational Assimilation ◽  
Coastal Ocean Model

scholarly journals Improving Surface Current Resolution Using Direction Finding Algorithms for Multiantenna High-Frequency Radars

2019 ◽  
Vol 36 (10) ◽  
pp. 1997-2014 ◽  
Author(s):  
Anthony Kirincich ◽  
Brian Emery ◽  
Libe Washburn ◽  
Pierre Flament
Keyword(s):  
Antenna Arrays ◽  
High Frequency ◽  
Surface Current ◽  
Likelihood Estimation ◽  
Direction Finding ◽  
Coastal Ocean ◽  
Hf Radar ◽  
Detection Methods ◽  
Multiple Signal Classification ◽  
Temporal And Spatial Variability

AbstractWhile land-based high-frequency (HF) radars are the only instruments capable of resolving both the temporal and spatial variability of surface currents in the coastal ocean, recent high-resolution views suggest that the coastal ocean is more complex than presently deployed radar systems are able to reveal. This work uses a hybrid system, having elements of both phased arrays and direction finding radars, to improve the azimuthal resolution of HF radars. Data from two radars deployed along the U.S. East Coast and configured as 8-antenna grid arrays were used to evaluate potential direction finding and signal, or emitter, detection methods. Direction finding methods such as maximum likelihood estimation generally performed better than the well-known multiple signal classification (MUSIC) method given identical emitter detection methods. However, accurately estimating the number of emitters present in HF radar observations is a challenge. As MUSIC’s direction-of-arrival (DOA) function permits simple empirical tests that dramatically aid the detection process, MUSIC was found to be the superior method in this study. The 8-antenna arrays were able to provide more accurate estimates of MUSIC’s noise subspace than typical 3-antenna systems, eliminating the need for a series of empirical parameters to control MUSIC’s performance. Code developed for this research has been made available in an online repository.

Toward Real-Time, Remote Observations of the Coastal Wind Resource Using High-Frequency Radar

2013 ◽  
Vol 47 (4) ◽  
pp. 206-217 ◽  
Author(s):  
Anthony Kirincich
Keyword(s):  
Wind Speed ◽  
High Frequency ◽  
Transfer Functions ◽  
Surface Wind ◽  
The United States ◽  
Coastal Ocean ◽  
Error Rates ◽  
Hf Radar ◽  
Variable Surface

AbstractThere is now a large installed base of high-frequency (HF) coastal ocean radars in the United States able to measure surface currents on an operational basis. However, these instruments also have the potential to provide estimates of the spatially variable surface wind field over distances ranging from 10 to 200 km offshore. This study investigates the ability of direction-finding HF radars to recover spatial maps of wind speed and direction from the dominant first-order region radar returns using empirical models. Observations of radar backscatter from the Martha’s Vineyard Coastal Observatory HF radar system were compared to wind observations from an offshore tower, finding significant correlations between wind speed and the backscatter power for a range of angles between the wind and radar loop directions. Models for the directional spreading of wind waves were analyzed in comparison to data-based results, finding potentially significant differences between the model and data-based spreading relationships. Using empirical fits, radar-based estimates of wind speed and direction at the location of the in situ wind sensor had error rates of 2 m/s and 60°, which decreased with hourly averaging. Attempts to extrapolate the results to the larger domain illustrated that spatially dependent transfer functions for wind speed and direction appear possible for large coastal ocean domains based on a small number of temporary, or potentially mobile, in situ wind sensors.

Do High-Frequency Radars Measure the Wave-Induced Stokes Drift?

2018 ◽  
Vol 35 (5) ◽  
pp. 1023-1031 ◽  
Author(s):  
Cédric Chavanne
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Wave Spectrum ◽  
Experimental Results ◽  
Hf Radar ◽  
Stokes Drift ◽  
Experimental Investigations ◽  
Specific Expression ◽  
Near Surface ◽  
Definitive Answer

ABSTRACTHigh-frequency (HF) radars remotely measure ocean near-surface currents based on the Doppler shift of electromagnetic waves backscattered by surface gravity waves with half the electromagnetic wavelength, called Bragg waves. Since their phase velocity is affected not only by wave–current interactions with vertically sheared mean Eulerian currents but also by wave–wave interactions with all the other waves present at the sea surface, HF radars should measure a quantity related to the Stokes drift in addition to mean Eulerian currents. However, the literature is inconsistent—both theoretically and experimentally—on the specific expression and even on the existence of the Stokes drift contribution to the HF radar measurements. Three different expressions that have been proposed in the literature are reviewed and discussed in light of the relevant published experimental results: 1) the weighted depth-averaged Stokes drift, 2) the filtered surface Stokes drift, and 3) half of the surface Stokes drift. Effective measurement depths for these three expressions are derived for the Phillips wave spectrum. Recent experimental results tend to discard the second expression but are not inconsistent with the first and third expressions. The latter is physically appealing, since it is a quasi-Eulerian quantity that would be measured by a current meter at a fixed horizontal position but allowed to follow the free surface moving vertically up and down with the passage of the waves. A definitive answer will require further experimental investigations.

scholarly journals Transformasi Gelombang Swell dan Gelombang Angin di Perairan Selatan Bali (Hal. 28-39)

2018 ◽  
Vol 4 (3) ◽  
pp. 28
Author(s):  
Fitri Suciaty
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Transformation Model ◽  
Wave Transformation ◽  
Major Influence ◽  
Observation Data ◽  
Swan Model ◽  
Nested Grids ◽  
The Indian Ocean ◽  
Wave Models

ABSTRAKGelombang swell dengan energi yang besar dan dapat menjalar hingga ratusan kilometer dari daerah pembangkitannya diketahui berpotensi merusak struktur pantai dan juga dapat mengganggu segala aktivitas yang dilakukan di pantai. Gelombang swell juga dinyatakan memberikan pengaruh yang besar pada inundasi yang terjadi di sepanjang pantai selatan Jawa dan Bali pada tanggal 4-9 Juni 2006 (Nugraheni, dkk., 2017). Studi transformasi gelombang swell dan gelombang angin di perairan selatan Bali dilakukan dengan pemodelan numerik  gelombang menggunakan model gelombang generasi ketiga SWAN model. Simulasi dilakukan dengan tiga nested grid dengan resolusi grid #1, #2 dan #3; masing-masing sebesar 0.05o, 0.005o, dan 0.001o. Simulasi dilakukan untuk dua buah skema pemodelan, yaitu model gelombang swell dan model gelombang angin. Hasil model menunjukan kesesuaian dengan data pengamatan. Hasil simulasi memperlihatkan gelombang swell yang berasal dari Samudera Hindia mendominasi kondisi gelombang di perairan selatan Bali selama periode simulasi (18 Desember 2011-6 Februari 2012). Dibandingkan dengan gelombang angin, gelombang swell menghasilkan tinggi gelombang yang lebih besar baik di lepas pantai maupun di area dekat pantai. Gelombang swell mengalami refraksi yang kuat di sekitar Bukit Peninsula.Kata kunci: gelombang Swell, gelombang angin, pemodelan transformasi gelombang. ABSTRACTSwells with its large energy can propagate up to hundreds of kilometers from the generation location. Therefore, swells have the potential to damage the structure of the coast and also can disrupt all activities carried out on the coast. Swells were also stated to have a major influence on the inundation that occurred along the southern coast of Java and Bali on June 4 to 9, 2006 (Nugraheni, et al., 2017). The study of swells and wind waves transformations in the waters of southern Bali is carried out by numerical wave modeling using a third generationwave model SWAN model. Nested grids are used with spatial resolution of grid #1, #2 and #3; is 0.05o, 0.005o, and 0.001o, respectively. Simulations are carried out for two modeling schemes that areswell models and wind wave models. The simulation shows compliance with observation data. The result shows swells originating from the Indian Ocean mostly dominated wave conditions in the waters of southern Bali during simulation period (18 Desember 2011-6 Februari 2012).  Compared to wind waves, swells produce higher wave both in offshore and coastal area. Swells experienced a strong refraction around the Bukit Peninsula.Keywords: swell, wind wave, wave transformation model.

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