scholarly journals Characteristics of high monsoon wind-waves observed at multiple stations in the eastern Arabian Sea

2017 ◽  
Author(s):  
M. M. Amrutha ◽  
V. Sanil Kumar
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Arabian Sea ◽  
Wind Waves ◽  
Surface Wind ◽  
Wave Model ◽  
Spatial Distance ◽  
Significant Wave ◽  
Eastern Arabian Sea ◽  
Crest Height

Abstract. The growth and decay of surface wind-waves during one-month period in a typical Indian summer monsoon is investigated based on the data collected at 9 to 15 m water depth at 4 locations in the nearshore waters of the eastern Arabian Sea covering a spatial distance of ~ 350 km. The significant wave height varied from 0.7 to 5.5 m during the data collection considered in the analysis. The heights of waves during the measurement period often exceed 3 m. The most extreme wave height is 1.50 to 1.62 times the significant wave height and the most extreme crest height of the wave is 1.23 to 1.35 times the significant wave height of the same 30-minutes record. The average ratio of crest height of the wave to the height of the same wave is 0.58 to 0.67. The height of waves having maximum crest height is smaller than the maximum wave height during 30 minutes period. Measured waves are predominantly swell, but since the majority of wave generation during the monsoon is adjacent to the study area and the wind–wave coupling is strong, wave periods are rarely above 15 s. The numerical wave model could estimate the wave height reasonably well during the wave growth compared to the wave decay period. Hovmöller diagrams show a considerable spatial variability in the wave and wind pattern in the Indian Ocean during the high wave event at the eastern Arabian Sea.

Effect of Uni- and Bi-Directional Coupling of Ocean-Met Interaction on Significant Wave Height and Local Wind

2017 ◽  
Author(s):  
Adil Rasheed ◽  
Jakob Kristoffer Süld ◽  
Mandar Tabib
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Surface Wind ◽  
Wave Model ◽  
Ocean Surface ◽  
Observation Data ◽  
Local Wind ◽  
Near Surface ◽  
Significant Wave ◽  
Bidirectional Coupling

Accurate prediction of near surface wind and wave height are important for many offshore activities like fishing, boating, surfing, installation and maintenance of marine structures. The current work investigates the use of different methodologies to make accurate predictions of significant wave height and local wind. The methodology consists of coupling an atmospheric code HARMONIE and a wave model WAM. Two different kinds of coupling methodologies: unidirectional and bidirectional coupling are tested. While in Unidirectional coupling only the effects of atmosphere on ocean surface are taken into account, in bidirectional coupling the effects of ocean surface on the atmosphere are also accounted for. The predicted values of wave height and local wind at 10m above the ocean surface using both the methodologies are compared against observation data. The results show that during windy conditions, a bidirectional coupling methodology has better prediction capability.

scholarly journals Wind Wave Growth at Short Fetch

2008 ◽  
Vol 38 (7) ◽  
pp. 1597-1606 ◽  
Author(s):  
T. Lamont-Smith ◽  
T. Waseda
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Significant Wave Height ◽  
Field Data ◽  
Wind Wave ◽  
Wind Waves ◽  
Retention Rates ◽  
Horizontal Distance ◽  
Wave Tank ◽  
Significant Wave

Abstract Wave wire data from the large wind wave tank of the Ocean Engineering Laboratory at the University of California, Santa Barbara, are analyzed, and comparisons are made with published data collected in four other wave tanks. The behavior of wind waves at various fetches (7–80 m) is very similar to the behavior observed in the other tanks. When the nondimensional frequency F* or nondimensional significant wave height H* is plotted against nondimensional fetch x*, a large scatter in the data points is found. Multivariate regression to the dimensional parameters shows that significant wave height Hsig is a function of U2x and frequency F is a function of U1.25x, where U is the wind speed and x is the horizontal distance, with the result that in general for wind waves at a particular fetch in a wave tank, approximately speaking, the wave frequency is inversely proportional to the square root of the wind speed and the wavelength is proportional to the wind speed. Similarly, the wave height is proportional to U1.5 and the orbital velocity is proportional to U. Comparison with field data indicates a transition from this fetch law to the conventional one [the Joint North Sea Wave Project (JONSWAP)] for longer fetch. Despite differences in the fetch relationship for the wave tank and the field data, the wave height and wave period satisfy Toba’s 3/2 power law. This law imposes a strong constraint on the evolution of wind wave energy and frequency; consequently, the energy and momentum retention rate are not independent. Both retention rates grow with wind speed and fetch at the short fetches present in the wave tank. The observed retention rates are completely different from those typically observed in the field, but the same constraint (Toba’s 3/2 law) holds true.

Uncertainty of Ocean Wave Hindcasts Due to Wind Modeling

1995 ◽  
Vol 117 (4) ◽  
pp. 294-297 ◽  
Author(s):  
J. C. Teixeira ◽  
M. P. Abreu ◽  
C. Guedes Soares
Keyword(s):  
Wind Speed ◽  
Relative Error ◽  
Wave Height ◽  
Significant Wave Height ◽  
Second Generation ◽  
Wave Model ◽  
Ocean Wave ◽  
Wind Fields ◽  
Significant Wave ◽  
Wind Input

Two wind models were developed and their results were compared with data gathered during the Wangara experiment, so as to characterize their uncertainty. One of the models was adopted to generate the wind fields used as input to a second generation wave model. The relative error in the wind speed was considered in order to assess the uncertainties of the predictions or the significant wave height. Different time steps for the wind input were also used to determine their effect on the predicted significant wave height.

scholarly journals Evaluation of Assimilation in the MASNUM Wave Model Based on Jason-3 and CFOSAT

2021 ◽  
Vol 13 (19) ◽  
pp. 3833
Author(s):  
Meng Sun ◽  
Jianting Du ◽  
Yongzeng Yang ◽  
Xunqiang Yin
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Ocean Waves ◽  
Validation Data ◽  
Engineering Construction ◽  
Significant Wave ◽  
Offshore Engineering ◽  
The Indian Ocean ◽  
Dynamic Sampling

Accurate numerical simulation of ocean waves is one of the most important measures to ensure shipping safety, offshore engineering construction, etc. The use of wave observations from satellite is an efficient way to correct model results. The goal of this paper is to assess the performance of assimilation in the MASNUM wave model for the Indian Ocean. The assimilation technique is based on Ensemble Adjusted Kalman Filter, with a variable ensemble constructed by the dynamic sampling method rather than ensemble members of wave model. Observations of significant wave height from satellites Jason-3 and CFOSAT are regarded as assimilation data and independent validation data, respectively. The results indicate good performance in terms of absolute mean error for significant wave height. Model error decreases by roughly 20–40% in high-sea conditions.

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.

Climatology, Variability and Extrema of Ocean Waves: The Web-Based KNMI/ERA-40 Wave Atlas

2006 ◽  
Author(s):  
Andreas Sterl ◽  
Sofia Caires
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Ocean Waves ◽  
Wave Period ◽  
Web Based ◽  
Significant Wave ◽  
Wave Parameters ◽  
Wave Heights ◽  
The Web

The European Centre for Medium Range Weather Forecasts (ECMWF) has recently finished ERA-40, a reanalysis covering the period September 1957 to August 2002. One of the products of ERA-40 consists of 6-hourly global fields of wave parameters like significant wave height and wave period. These data have been generated with the Centre’s WAM wave model. From these results the authors have derived climatologies of important wave parameters, including significant wave height, mean wave period, and extreme significant wave heights. Particular emphasis is on the variability of these parameters, both in space and time. Besides for scientists studying climate change, these results are also important for engineers who have to design maritime constructions. This paper describes the ERA-40 data and gives an overview of the results derived. The results are available on a global 1.5° × 1.5° grid. They are accessible from the web-based KNMI/ERA-40 Wave Atlas at http://www.knmi.nl/waveatlas.

Error estimation of buoy, altimeter, and model significant wave height from triple collocation technique

2021 ◽  
Author(s):  
Guillaume Dodet ◽  
Jean-Raymond Bidlot ◽  
Mickaël Accensi ◽  
Mathias Alday ◽  
Saleh Abdalla ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Sea State ◽  
Significant Wave ◽  
In Situ Data ◽  
Collocation Technique ◽  
Coastal Risk ◽  
Marine Engineering

<p>Ocean wave information is of major importance for a number of applications including climate studies, safety at sea, marine engineering (offshore and coastal), and coastal risk management. Depending on the scales and regions of interest, several data sources may be considered (e.g. in situ data, VOS observations, altimeter records, numerical wave model), each one with its pros and cons. In order to optimize the use of multiple source wave information (e.g. through assimilation scheme in NWP), the error characteristics of each measurement system need to be investigated and inter-compared. In this study, we use triple collocation technique to estimate the random error variances of significant wave height from in situ, altimeter and model data. The buoy dataset is a selection of ~100 in-situ measuring stations provided by the CMEMS In-Situ Thematic Assembly Center. The altimeter dataset is composed of the ESA Sea State CCI V1.1 L2P product. The model dataset is the result of WW3 Ifremer hindcast run forced with ERA5 winds using the recently updated T475 parameterization. In comparisons to previous studies using similar techniques, the large triple collocation dataset (~450 000 matchups in total) generated for this study provides some new insights on the error variability within in situ stations, satellite missions and upon sea state conditions.Moreover, the results of the triple collocation technique help developing improved calibration of the altimeter missions included in the ESA Sea State CCI V1.1 dataset.</p>

scholarly journals CLTS-Net: A More Accurate and Universal Method for the Long-Term Prediction of Significant Wave Height

2021 ◽  
Vol 9 (12) ◽  
pp. 1464
Author(s):  
Shuang Li ◽  
Peng Hao ◽  
Chengcheng Yu ◽  
Gengkun Wu
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Multivariate Time Series ◽  
Surface Wind ◽  
Correlation Coefficients ◽  
Climatic Data ◽  
Universal Method ◽  
Significant Wave ◽  
Multiple Variables

Significant wave height (SWH) prediction plays an important role in marine engineering areas such as fishery, exploration, power generation, and ocean transportation. For long-term forecasting of a specific location, classical numerical model wave height forecasting methods often require detailed climatic data and incur considerable calculation costs, which are often impractical in emergencies. In addition, how to capture and use the dynamic correlation between multiple variables is also a major research challenge for multivariate SWH prediction. To explore a new method for predicting SWH, this paper proposes a deep neural network model for multivariate time series SWH prediction—namely, CLTS-Net. In this study, the sea surface wind and wave height in the ERA5 dataset of the relevant points P1, P2, and P3 from 2011 to 2018 were used as input information to train the model and evaluate the model’s SWH prediction performance. The results show that the correlation coefficients (R) of CLTS-Net are 0.99 and 0.99, respectively, in the 24 h and 48 h SWH forecasts at point P1 along the coast. Compared with the current mainstream artificial intelligence-based SWH solutions, it is much higher than ANN (0.79, 0.70), RNN (0.82, 0.83), LSTM (0.93, 0.91), and Bi-LSTM (0.95, 0.94). Point P3 is located in the deep sea. In the 24 h and 48 h SWH forecasts, the R of CLTS-Net is 0.97 and 0.98, respectively, which are much higher than ANN (0.71, 0.72), RNN (0.85, 0.78), LSTM (0.85, 0.78), and Bi-LSTM (0.93, 0.93). Especially in the 72 h SWH forecast, when other methods have too large errors and have lost their practical application value, the R of CLTS-Net at P1, P2, and P3 can still reach 0.81, 0.71, and 0.98. The results also show that CLTS-Net can capture the short-term and long-term dependencies of data, so as to accurately predict long-term SWH, and has wide applicability in different sea areas.

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