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 Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone

2020 ◽  
Vol 8 (12) ◽  
pp. 1039
Author(s):  
Ben Timmermans ◽  
Andrew G. P. Shaw ◽  
Christine Gommenginger
Keyword(s):  
Coastal Zone ◽  
Wave Height ◽  
Satellite Data ◽  
Significant Wave Height ◽  
Wave Climate ◽  
In Situ Measurements ◽  
Altimeter Data ◽  
Sea State ◽  
Significant Wave

Measurements of significant wave height from satellite altimeter missions are finding increasing application in investigations of wave climate, sea state variability and trends, in particular as the means to mitigate the general sparsity of in situ measurements. However, many questions remain over the suitability of altimeter data for the representation of extreme sea states and applications in the coastal zone. In this paper, the limitations of altimeter data to estimate coastal Hs extremes (<10 km from shore) are investigated using the European Space Agency Sea State Climate Change Initiative L2P altimeter data v1.1 product recently released. This Sea State CCI product provides near complete global coverage and a continuous record of 28 years. It is used here together with in situ data from moored wave buoys at six sites around the coast of the United States. The limitations of estimating extreme values based on satellite data are quantified and linked to several factors including the impact of data corruption nearshore, the influence of coastline morphology and local wave climate dynamics, and the spatio-temporal sampling achieved by altimeters. The factors combine to lead to considerable underestimation of estimated Hs 10-yr return levels. Sensitivity to these factors is evaluated at specific sites, leading to recommendations about the use of satellite data to estimate extremes and their temporal evolution in coastal environments.

scholarly journals Evaluation of Sentinel-3A Wave Height Observations Near the Coast of Southwest England

2019 ◽  
Vol 11 (24) ◽  
pp. 2998 ◽  
Author(s):  
Francesco Nencioli ◽  
Graham D. Quartly
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Wave Height ◽  
Significant Wave Height ◽  
Mean Square ◽  
Significant Wave ◽  
In Situ Observations ◽  
Regression Slopes

Due to the smaller ground footprint and higher spatial resolution of the Synthetic Aperture Radar (SAR) mode, altimeter observations from the Sentinel-3 satellites are expected to be overall more accurate in coastal areas than conventional nadir altimetry. The performance of Sentinel-3A in the coastal region of southwest England was assessed by comparing SAR mode observations of significant wave height against those of Pseudo Low Resolution Mode (PLRM). Sentinel-3A observations were evaluated against in-situ observations from a network of 17 coastal wave buoys, which provided continuous time-series of hourly values of significant wave height, period and direction. As the buoys are evenly distributed along the coast of southwest England, they are representative of a broad range of morphological configurations and swell conditions against which to assess Sentinel-3 SAR observations. The analysis indicates that SAR observations outperform PLRM within 15 km from the coast. Within that region, regression slopes between SAR and buoy observations are close to the 1:1 relation, and the average root mean square error between the two is 0.46 ± 0.14 m. On the other hand, regression slopes for PLRM observations rapidly deviate from the 1:1 relation, while the average root mean square error increases to 0.84 ± 0.45 m. The analysis did not identify any dependence of the bias between SAR and in-situ observation on the swell period or direction. The validation is based on a synergistic approach which combines satellite and in-situ observations with innovative use of numerical wave model output to help inform the choice of comparison regions. Such an approach could be successfully applied in future studies to assess the performance of SAR observations over other combinations of coastal regions and altimeters.

scholarly journals Round Robin Assessment of Radar Altimeter Low Resolution Mode and Delay-Doppler Retracking Algorithms for Significant Wave Height

2020 ◽  
Vol 12 (8) ◽  
pp. 1254 ◽  
Author(s):  
Florian Schlembach ◽  
Marcello Passaro ◽  
Graham D. Quartly ◽  
Andrey Kurekin ◽  
Francesco Nencioli ◽  
...  
Keyword(s):  
Climate Change ◽  
Wave Height ◽  
Significant Wave Height ◽  
Low Resolution ◽  
Spectral Variability ◽  
Sea State ◽  
Significant Wave ◽  
In Situ Data ◽  
Wave Models

Radar altimeters have been measuring ocean significant wave height for more than three decades, with their data used to record the severity of storms, the mixing of surface waters and the potential threats to offshore structures and low-lying land, and to improve operational wave forecasting. Understanding climate change and long-term planning for enhanced storm and flooding hazards are imposing more stringent requirements on the robustness, precision, and accuracy of the estimates than have hitherto been needed. Taking advantage of novel retracking algorithms, particularly developed for the coastal zone, the present work aims at establishing an objective baseline processing chain for wave height retrieval that can be adapted to all satellite missions. In order to determine the best performing retracking algorithm for both Low Resolution Mode and Delay-Doppler altimetry, an objective assessment is conducted in the framework of the European Space Agency Sea State Climate Change Initiative project. All algorithms process the same Level-1 input dataset covering a time-period of up to two years. As a reference for validation, an ERA5-based hindcast wave model as well as an in-situ buoy dataset from the Copernicus Marine Environment Monitoring Service In Situ Thematic Centre database are used. Five different metrics are evaluated: percentage and types of outliers, level of measurement noise, wave spectral variability, comparison against wave models, and comparison against in-situ data. The metrics are evaluated as a function of the distance to the nearest coast and the sea state. The results of the assessment show that all novel retracking algorithms perform better in the majority of the metrics than the baseline algorithms currently used for operational generation of the products. Nevertheless, the performance of the retrackers strongly differ depending on the coastal proximity and the sea state. Some retrackers show high correlations with the wave models and in-situ data but significantly under- or overestimate large-scale spectral variability. We propose a weighting scheme to select the most suitable retrackers for the Sea State Climate Change Initiative programme.

scholarly journals Wave Climate Change in the North Sea and Baltic Sea

2019 ◽  
Vol 7 (6) ◽  
pp. 166 ◽  
Author(s):  
Antonio Bonaduce ◽  
Joanna Staneva ◽  
Arno Behrens ◽  
Jean-Raymond Bidlot ◽  
Renate Anna Irma Wilcke
Keyword(s):  
Climate Change ◽  
Baltic Sea ◽  
Wave Height ◽  
North Sea ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Significant Wave ◽  
The North ◽  
The North Sea

Wave climate change by the end of the 21st century (2075–2100) was investigated using a regional wave climate projection under the RCP 8.5 scenario. The performance of the historical run (1980–2005) in representing the present wave climate was assessed when compared with in situ (e.g., GTS) and remote sensing (i.e., Jason-1) observations and wave hindcasts (e.g., ERA5-hindcast). Compared with significant wave height observations in different subdomains, errors on the order of 20–30% were observed. A Principal Component (PC) analysis showed that the temporal leading modes obtained from in situ data were well correlated (0.9) with those from the historical run. Despite systematic differences (10%), the general features of the present wave climate were captured by the historical run. In the future climate projection, with respect to the historical run, similar wave climate change patterns were observed when considering both the mean and severe wave conditions, which were generally larger during summer. The range of variation in the projected extremes (±10%) was consistent with those observed in previous studies both at the global and regional spatial scales. The most interesting feature was the projected increase in extreme wind speed, surface Stokes drift speed and significant wave height in the Northeast Atlantic. On the other hand, a decrease was observed in the North Sea and the southern part of the Baltic Sea basin, while increased extreme values occurred in the Gulf of Bothnia during winter.

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

&lt;p&gt;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.&lt;/p&gt;

scholarly journals Oceanographic habitat and the coral microbiomes of urban-impacted reefs

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7552 ◽  
Author(s):  
Stephanie M. Rosales ◽  
Christopher Sinigalliano ◽  
Maribeth Gidley ◽  
Paul R. Jones ◽  
Lewis J. Gramer
Keyword(s):  
Wave Height ◽  
Relative Abundance ◽  
Significant Wave Height ◽  
High Throughput Sequencing ◽  
Numerical Models ◽  
Sea Temperature ◽  
Significant Wave ◽  
Coral Microbiome ◽  
Coral Health

Coral reefs are in decline worldwide. In response to this habitat loss, there are efforts to grow, outplant, and restore corals in many regions. The physical oceanographic habitat of corals—such as sea temperature, waves, ocean currents, and available light—is spatially heterogeneous. We therefore hypothesize that outplant location may affect microbiomes, and ultimately, coral health and restoration success. We evaluated the influence of the physical oceanographic habitat on microbes in wild Porites astreoides and Siderastrea siderea. Tissue samples were collected at four Florida reefs in March, June, and September of 2015. We estimated oceanographic conditions from moored instruments, diver observations, remote sensing data, and numerical models. We analyzed microbiomes using amplicon 16S rRNA high-throughput sequencing data. We found microbial alpha-diversity negatively correlated with in situ sea temperature (which represented both the annual cycle and upwelling), as well as modeled alongshore currents, in situ sea-level, and modeled tide. Microbial beta-diversity correlated positively with significant wave height and alongshore currents from models, remotely-sensed relative turbidity, and in situ temperature. We found that archaea from the order Marine Group II decrease with increases in significant wave height, suggesting that this taxon may be influenced by waves. Also, during times of high wave activity, the relative abundance of bacteria from the order Flavobacteriales increases, which may be due to resuspension and cross-shelf transport of sediments. We also found that bacteria from the order SAR86 increase in relative abundance with increased temperature, which suggests that this taxon may play a role in the coral microbiome during periods of higher temperature. Overall, we find that physical oceanographic variability correlates with the structure of these coral microbiomes in ways that could be significant to coral health.

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.

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