scholarly journals A Wave Measurements HF Radar Data Set in the Malta-Sicily Channel: Data Quality, Validation and Gap Filling

10.29007/wg8s ◽  
2018 ◽  
Author(s):  
Marco Picone ◽  
Arianna Orasi ◽  
Aldo Drago ◽  
Fulvio Capodici ◽  
Giuseppe Ciraolo ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Missing Values ◽  
Hf Radar ◽  
Data Set ◽  
Significant Wave ◽  
Wave Data ◽  
Wave Measurements ◽  
Sicily Channel ◽  
Radar Wave

The CALYPSO HF radar network is a permanent and fully operational observing system currently composed of four CODAR HF stations. The system is providing real- time hourly maps of sea surface currents and wave data in the Malta-Sicily Channel since 2012. Significant wave height derived from the HF radar wave measurements are confirmed to be a reliable source of wave information even in case of extreme events. However, it is noticed that the HF radar wave data are subject to differing interfering noise in the signal from unknown sources that may be competing with transmissions in the same frequency band. These interferences lead to frequent gaps and/or outliers that affect the continuity and reliability of the data set. The aim of this work is to estimate missing values and to detect possible outliers building and fitting a Markov chain mixture model on the significant wave height data collected at the four stations. It is verified that the proposed procedure is sufficiently robust since the model estimates succeed to classify radar observations with a high percentage of missing data and to equally highlight spikes and outliers.

scholarly journals VALIDATION OF JASON-2 AND ENVISAT WIND SPEED AND SIGNIFICANT WAVE HEIGHT DATA IN THE INTERTROPICAL ZONE

2013 ◽  
Vol 31 (3) ◽  
pp. 483 ◽  
Author(s):  
Guilherme Colaço Melo Dos Passos ◽  
Nelson Violante Carvalho ◽  
Uggo Ferreira Pinho ◽  
Alexandre Pereira Cabral ◽  
Frederico F. Ostritz
Keyword(s):  
Wind Speed ◽  
Correlation Coefficient ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wind Waves ◽  
Altimeter Data ◽  
Data Set ◽  
Significant Wave ◽  
Wave Measurements ◽  
Satellite Radar

ABSTRACT. The estimates of significant wave height (SWH) and wind speed at 10 meter height (u10) from the Jason-2 and ENVISAT satellites, over the intertropical region, are analysed. Some authors have tested the dependency of satellite radar wind/wave measurements on local environmental conditions, particularly on wave age, with no conclusive results. Our data show that Jason-2 overestimates high values of SWH and underestimates low values, while ENVISAT exhibits the opposite behaviour. The correlation coefficient between buoy measurements and altimeter data is around 0.95, with bias and root mean square error (RMSE) of, 3 and 15 cm respectively. On the other hand, Jason-2 underestimates u10 throughout the whole measured range, while ENVISAT overestimates throughout the whole range for speeds over 3 m/s. The correlation coefficient is around 0.90, with bias and RMSE around 0.20 cm and 1.5 m/s, respectively. The altimeter estimates in the intertropical region are similar to those obtained with global coverage, hence the sensitivity to sea state to extract wind speed and wave height is not so obvious in our data set. Therefore, the results indicate that the algorithms employed have a fair enough performance in the intertropical region.Keywords: wind waves, wind speed, altimeter, Jason-2, ENVISAT. RESUMO. As estimativas de altura significativa de onda (SWH) e de intensidade do vento a 10 metros de altura (u10) dos altímetros dos satélites Jason-2 e ENVISAT, obtidas na região intertropical, são analisadas. Alguns trabalhos apontam para uma possível dependência da esbeltez das ondas, e portanto do estado de mar, para extração de u10 e SWH, o que tornaria os algoritmos empregados dependentes da localidade. Os resultados aqui obtidos mostram que o Jason-2 em geral superestima altos valores de SWH e subestima baixos valores, enquanto que para o ENVISAT a tendência encontrada é a inversa. Foram obtidos coeficientes de correlação entre a SWH de boias e dos altímetros em torno de 0,95, e bias e erro médio quadrático (RMSE) de aproximadamente 3 e 15 cm, respectivamente. Em relação à u10, o Jason-2 subestima ligeiramente os valores, independente da faixa de intensidade do vento, enquanto que o ENVISAT os superestimam em quase todas as faixas de intensidade, exceto para ventos menores que 3 c/s. Os coeficientes de correlação se encontram em torno de 0,90, com bias e erro médio quadrático de, respectivamente, aproximadamente 0,20 cm e 1,5 c/s. Os resultados indicam que o desempenho na região intertropical é similar aos resultados obtidos empregando medições globais, que são altamente concentradas em altas latitudes no Hemisfério Norte. O efeito da condição do estado de mar para extração de SWH e u10, caso seja importante, não aparenta ser considerável no conjunto de dados aqui empregado. Portanto, os resultados apontam para um desempenho bastante aceitável de tais algoritmos quando empregados na região intertropical.Palavras-chave: altura significativa de ondas, intensidade do vento, altimetria, Jason-2, ENVISAT.

scholarly journals Assessment of Significant Wave Height in the Taiwan Strait Measured by a Single HF Radar System

2019 ◽  
Vol 36 (7) ◽  
pp. 1419-1432 ◽  
Author(s):  
Linghui Cai ◽  
Shaoping Shang ◽  
Guomei Wei ◽  
Zhigang He ◽  
Yanshuang Xie ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Absolute Error ◽  
Taiwan Strait ◽  
Radar System ◽  
Hf Radar ◽  
Study Region ◽  
Significant Wave ◽  
Wave Measurements

AbstractDual high-frequency (HF) radar systems are often used to provide measurements of waves, winds, and currents. In this study, the accuracy of wave measurements using a single HF radar system (OS081H-A) was explored using datasets obtained during 5–27 January 2014 in the southwestern Taiwan Strait. We selected the study region as an area with >90% coverage (i.e., the range was <100 km). Qualitative and quantitative intercomparison of wave measurements (by the radar and five buoys) and wave model products [from the Simulating Wave Nearshore (SWAN) model] were conducted. Intercomparison of the modeled and in situ significant wave height Hs showed that the model-predicted Hs could be considered to be acceptable for use as “sea truth” to evaluate the radar-derived Hs, with mean bias from −0.45 to −0.16 m, mean absolute error (MAE) of 0.24–0.45 m, and root-mean-square error of 0.31–0.54 m. It was found that the MAE of radar-derived Hs was ≤ 1 m for 86% of the sector (except at the edge of sector) when the model-predicted Hs was ≥ 1.5 m. In particular, the MAE was less than 0.6 m for 63% of the sector, which was mainly distributed in the area with a bearing from −50° to +70° and a range of 20–70 km. The results are promising, but more work is needed. We employed a spatial distribution function for the MAE of the radar-derived Hs over the sample duration based on range, bearing, and mean radar-derived Hs.

Comparison of Bivariate Models of the Distribution of Significant Wave Height and Peak Wave Period

2007 ◽  
Author(s):  
Catarina S. Soares ◽  
C. Guedes Soares
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Bivariate Normal Distribution ◽  
Wave Period ◽  
Peak Period ◽  
Data Set ◽  
Significant Wave ◽  
The North ◽  
Bivariate Models ◽  
The North Sea

This paper presents the results of a comparison of the fit of three bivariate models to a set of 14 years of significant wave height and peak wave period data from the North Sea. One of the methods defines the joint distribution from a marginal distribution of significant wave height and a set of distributions of peak period conditional on significant wave height. Other method applies the Plackett model to the data and the third one applies the Box-Cox transformation to the data in order to make it approximately normal and then fits a bivariate normal distribution to the transformed data set. It is shown that all methods provide a good fit but each one have its own strengths and weaknesses, being the choice dependent on the data available and applications in mind.

scholarly journals Wave Observations from Central California: SeaSonde Systems andIn SituWave Buoys

2011 ◽  
Vol 2011 ◽  
pp. 1-18 ◽  
Author(s):  
Regan M. Long ◽  
Don Barrick ◽  
John L. Largier ◽  
Newell Garfield
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Strong Correlations ◽  
California Coast ◽  
Central California ◽  
Significant Wave ◽  
Wave Data ◽  
Reliable Source ◽  
Buoy Data

Wave data from five 12-13 MHz SeaSondes radars along the central California coast were analyzed to evaluate the utility of operational wave parameters, including significant wave height, period, and direction. Data from fourin situwave buoys served to verify SeaSonde data and independently corroborate wave variability. Hourly averaged measurements spanned distance is 150 km alongshore × 45 km offshore. Individual SeaSondes showed statistically insignificant variation over 27 km in range. Wave height inter-comparisons between regional buoys exhibit strong correlations, approximately 0.93, and RMS differences less than 50 cm over the region. SeaSonde-derived wave data were compared to nearby buoys over timescales from 15 to 26 months, and revealed wave height correlations and mean RMS difference of 53 cm. Results showed that height RMS differences are a percentage of significant wave height, rather than being constant independent of sea state. Period and directions compared favorably among radars, buoys, and the CDIP model. Results presented here suggest that SeaSondes are a reliable source of wave information. Supported by buoy data, they also reveal minimal spatial variation in significant wave height, period, and direction in coastal waters from ~45 km × ~150 km in this region of the central California coast. Small differences are explained by sheltering from coastal promontories, and cutoff boundaries in the case of the radars.

scholarly journals An Empirical Algorithm to Retrieve Significant Wave Height from Sentinel-1 Synthetic Aperture Radar Imagery Collected under Cyclonic Conditions

2018 ◽  
Vol 10 (9) ◽  
pp. 1367 ◽  
Author(s):  
Weizeng Shao ◽  
Yuyi Hu ◽  
Jingsong Yang ◽  
Ferdinando Nunziata ◽  
Jian Sun ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Wave Height ◽  
Significant Wave Height ◽  
Synthetic Aperture ◽  
Training Dataset ◽  
Sar Images ◽  
Data Set ◽  
Significant Wave ◽  
Sar Imagery ◽  
Aperture Radar

In this study, an empirical algorithm is proposed to retrieve significant wave height (SWH) from dual-polarization Sentinel-1 (S-1) synthetic aperture radar (SAR) imagery collected under cyclonic conditions. The retrieval scheme is based on the well-known CWAVE empirical function that is here updated to deal with multi-polarization S-1 SAR measurements collected using the interferometric wide (IW) and the Extra Wide-Swath (EW) imaging modes, under cyclonic conditions. First, a training dataset that consists of six S-1 SAR images collected under cyclonic conditions is exploited to both tune the retrieval function and to check the soundness of the retrievals against the co-located WAVEWATCH-III (WW3) numerical simulations. The comparison of simulation from the WW3 model and measurements from altimeter Jason-2 shows a 0.29m root mean square error (RMSE) of significant wave height (SWH). Then, a testing data-set that consists of two S-1 SAR images is exploited to provide a preliminary validation. The results, verified against both WW3 and European Centre for Medium-Range Weather Forecasts (ECMWF) data, show the soundness of the herein approach.

Comparative wave measurements at a wave energy site with a recently developed low-cost wave buoy (Spotter), ADCP and pressure loggers

2021 ◽  
Author(s):  
Orrin Lancaster ◽  
Remo Cossu ◽  
Sebastien Boulay ◽  
Scott Hunter ◽  
Tom E. Baldock
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Low Cost ◽  
Wave Period ◽  
Wave Direction ◽  
Mean Values ◽  
Significant Wave ◽  
Wave Measurements ◽  
The Mean

AbstractWave measurements from a new, low-cost, real-time wave buoy (Spotter) are investigated in a comparative study as part of a site characterization study at a wave energy candidate site at King Island, Tasmania, Australia. Measurements from the Sofar Ocean Spotter buoy are compared with concurrent measurements from a Teledyne RD Instrument (RDI) 1200 kHz Work Horse ADCP and two RBRsolo3 D wave16 pressure loggers. The comparison period between 8th August – 12th October 2019 provides both the shallowest and longest continuous published comparison undertaken with the Spotter buoy.Strong agreement was evident between the Spotter buoy and RDI ADCP of key wave parameters including the significant wave height, peak wave period, and mean wave direction, with the mean values of those parameters across the full deployment period agreeing within 3%. Surface wave spectra and directional spectra are also analyzed with good agreement observed over the majority of the frequency domain, although the Spotter buoy records approximately 17% less energy within a narrow frequency band near the peak frequency when compared to the RDI ADCP. Measurements derived from the pressure loggers routinely underestimated the significant wave height and overestimated the mean wave period over the deployment period. The comparison highlights the suitability of the Spotter buoy for low-cost wave resource studies, with accurate measurements of key parameters and spectra observed.

Comparison of VOS and ERA-Interim Wave Data

2019 ◽  
Author(s):  
Roberto Vettor ◽  
C. Guedes Soares
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Numerical Data ◽  
Previous Literature ◽  
Significant Wave ◽  
Wave Data ◽  
Systematic Biases ◽  
One To One

Abstract Accuracy of Voluntary Observing Ship’s reports is evaluated by a one-to-one comparison with ERA-interim database, specifically considering significant wave height. A first screening allows to detect the most common and undeniable mistakes, as for instance clear errors in reporting the position of the vessel, and delete these observations. Moreover, previous literature is considered to remove systematic biases. Then each report is matched with the appropriate numerical data in terms of location and time, in order to evaluate the scattering of the data, to identify the outliers, and to further prune the database. The procedure allows not only to maintain a database clean from clearly wrong information, which can compromise the statistics, but also to recognize areas and conditions in which the mismatch between numerical data and observations is critical, eventually speculating on the motivations.

scholarly journals STATISTICAL MODELLING OF LONG-TERM WAVE CLIMATES

1986 ◽  
Vol 1 (20) ◽  
pp. 4 ◽  
Author(s):  
Richard Burrows ◽  
Barham A. Salih
Keyword(s):  
Data Base ◽  
Wave Height ◽  
Significant Wave Height ◽  
Joint Probability ◽  
Statistical Modelling ◽  
Wave Climate ◽  
Statistical Properties ◽  
Significant Wave ◽  
Wave Data

The paper discusses the long-term statistical properties of ocean and coastal wave climates derived from the analysis of instrumental wave data. The aim of the work reported has been to determine the theoretical distributions, from those commonly used in analysis of wave data, which best describe the joint probability of significant wave height, Hs, and mean zero-upcrossing period, Tz. A method of modelling the wave climate in this manner has been developed utilizing parametric means of specification. The data base used in the study covers records from 18 sites around the British Isles.

scholarly journals A New Method of Wave Mapping with HF Radar

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Lijie Jin ◽  
Biyang Wen ◽  
Hao Zhou
Keyword(s):  
Wave Height ◽  
Second Harmonic ◽  
Mapping Method ◽  
Hf Radar ◽  
Great Success ◽  
Broad Beam ◽  
Wave Measurements ◽  
Wave Inversion ◽  
Local Wave ◽  
Radar Wave

Study of wave height inversion with High-Frequency Surface Wave Radars (HFSWRs) has been going on for more than 40 years. Various wave inversion methods have been proposed, and HFSWRs have achieved great success in local wave measurements. However, the method of wave mapping is still under development, especially for the broad-beam HF radars. Existing methods of wave mapping are based on narrow-beam radar with beamforming. This paper introduces a way of wave height inversion, using the ratio of the second-harmonic peak (SHP) to the Bragg peak (RSB). A new wave mapping method is proposed, which can be used in both narrow and broad-beam radars, according to the way of wave inversion based on the RSB. In addition, radar wave measurements at the buoy position are compared with thein situbuoy, which show a good agreement. At last, the results of wave mapping on the two-hour timescale are given.

Sign in / Sign up

Export Citation Format

Share Document