Trends In Wave Height Research Articles

Analysis of wave characteristics near the pilot station

As one of the primary services ports provide, pilotage services aim to ensure the safe passage of vessels when entering and leaving the port. This study uses Taichung Port, located in the central part of the Taiwan Strait, as an example to analyze the impact of monsoon characteristics on wave conditions at pilot boarding points and to highlight their crucial role in safeguarding pilot boarding safety. By analyzing data from the ADCP (Acoustic Doppler Current Profiler) station north of the port’s northern breakwater and the Taichung buoy located southwest of the port, compare wave height distributions at the boarding point. The research addresses the impact of current and planned expansions, including constructing a new LNG receiving terminal with extended breakwaters, on wave dynamics and pilot operations. The study demonstrates that data from multiple sources—such as ADCP and buoy measurements—helps mitigate issues caused by missing data from specific stations. The analysis shows that numerical values differ slightly, while wave height trends at the boarding point are similar under current and expanded port conditions. The study concludes that the proposed expansion will likely affect wave diffraction patterns but will enhance the predictability and safety of boarding operations by reducing uncertainties associated with single measurement stations. Overall, the results of this study can enhance the understanding of marine meteorological information, improve the safety of pilot boarding operations, and thereby increase the efficiency and safety of port operations.

Accurate storm surge prediction in hurricane area of the Atlantic Ocean using a new multi-recursive neural network based on gate recursive unit

This paper proposes an enhanced storm surge forecasting approach utilizing novel neural networks, specifically a model based on gated recurrent units (GRUs), and incorporates a distortion loss function known as Distortion Loss Including Shape and Time (DILATE) for improved prediction accuracy and reliability. Historical data from four stations in the hurricane-prone region of the Atlantic Ocean are utilized for both training and testing purposes. Various models are employed to predict storm surges with lead times of 3, 6, and 12 hours, and their performance is evaluated by comparing the predicted values with the observed ones. Furthermore, the influence of various physical factors on storm surge formation is examined. The findings indicate that the GRU-DILATE model is more suitable for storm surge prediction, particularly for longer lead times. This model effectively reduces prediction delays and accurately captures the trends in wave height associated with storm surges. Among the physical factors studied, wind speed and atmospheric pressure emerge as the most important variables influencing storm surges. Additionally, the significance of wind direction is highlighted, as it plays a crucial role in determining whether the sea level rises or falls during the initial stages of a storm surge. It is expected that the proposed model has the potential to enhance response and preparedness measures in hurricane-prone areas, finding applications in coastal planning, infrastructure design, disaster management, and other aspects of ocean engineering.

Trends in ocean waves climate within the Mediterranean Sea: a review

The interest for the impact of climate change on ocean waves within the Mediterranean Sea has motivated a number of studies aimed at identifying trends in sea states parameters from historical multi-decadal wave records. In the last two decades progress in computing and the availability of suitable time series from observations further supported research on this topic. With the aim of identifying consensus among previous research on the Mediterranean Sea and its sub-basins, this review analysed the results presented in peer reviewed articles researching historical ocean waves trends published after the year 2000. Most studies focused on the significant wave height trends, while direction and wave period appear to be under-studied in this context. We analysed trends in mean wave climate and extreme sea states. We divided the Mediterranean basin in 12 sub-basins and analysed the results available in the literature from a wide range of data sources, such as satellite altimetry and numerical models, among others. The consensus on the significant wave height mean climate trends is limited, while statistically significant trends in extreme values are detected in the western Mediterranean Sea, in particular in the Gulf of Lion and in the Tyrrhenian Sea, with complex spatial distributions. Negative extreme sea state trends in the sub-basins, although frequently identified, are mostly not significant. We discuss the sources of uncertainty in results introduced by the data used, statistics employed to characterise mean or extreme conditions, length of the time period used for the analysis, and thresholds used to prove trends statistical significance. The reduction of such uncertainties, and the relationship between trends in sea states and weather processes are identified as priority for future research.

Time of Emergence for Altimetry‐Based Significant Wave Height Changes in the North Atlantic

AbstractSatellite observations of significant wave height (Hs) have recently reached 30 years of continuous record. Is this length sufficient to detect the effect of anthropogenically forced climate change on wave height trends? Wave height decadal variability is influenced by a combination of internal variability and forced variability caused by both anthropogenic and natural forcing. Using a statistical model to derive Hs from sea level pressure field and exploiting ERA‐5 reanalysis data as well as 80 members of the Community Earth System Model v2 large ensemble, we show that, over the North Atlantic (NA), altimetry‐based Hs trends are mostly caused by internal variability. This suggests that Hs changes computed over the satellite era are not yet controlled by anthropogenic climate change. Starting from 1993, the date of emergence, defined as the date when the forced signal becomes dominant over the internal variability, is later than 2050 for Hs in the NA.

Моделирование ветрового волнения в море Лаптевых, Восточно-Сибирском и Чукотском морях

The paper presents an analysis of wind wave parameters in the Laptev, East Siberian and Chukchi seas based on the results of numerical experiments with the WAVEWATCH III wave model for a period from 1979 to 2021. Wave modeling was carried out using an unstructured computational grid with a high resolution (up to 800 m) in the coastal zone. The NCEP/CFSR/CFSv2 reanalysis was used as wind forcing. The maps of the long-term mean values of the wave height, wave length and period were obtained. For the several points in the central part of each sea, the mean annual values of wave heights are calculated and the analysis of interannual variability is carried out. The maximum significant wave height was 5–6 m in the Laptev Sea, 6–7 m in the East Siberian Sea, and 7–7.5 m in the Chukchi Sea. The analysis of interannual variability showed that there is a positive trend in wave height for all seas under consideration. The largest increase in the annual mean wave height is observed in the East Siberian Sea (from 0.4 to 1.4 m in the ice-free period). Keywords: Laptev Sea, Chukchi Sea, East Siberian Sea, wave modeling, Arctic wind waves, WAVEWATCH III

Can Multi-Mission Altimeter Datasets Accurately Measure Long-Term Trends in Wave Height?

A long-duration, multi-mission altimeter dataset is analyzed to determine its accuracy in determining long-term trends in significant wave height. Two calibration methods are investigated: “altimeter–buoy” calibration and “altimeter–altimeter” calibration. The “altimeter–altimeter” approach shows larger positive trends globally, but both approaches are subject to temporal non-homogeneity between altimeter missions. This limits the accuracy of such datasets to approximately ±0.2 cm/year in determining trends in significant wave height. The sampling pattern of the altimeters is also investigated to determine if under-sampling impacts the ability of altimeters to measure trends for higher percentiles. It is concluded that, at the 99th percentile level, sampling issues result in a positive bias in values of trend. At lower percentiles (90th and mean), the sampling issues do not bias the trend estimates significantly.

Wave Height Trends off Central West Coast of India

Kerkar, J.P.; Seelam, J.K., and Jena, B.K., 2020. Wave height trends off central west coast of India. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 97-104. Coconut Creek (Florida), ISSN 0749-0208.Wave height trends off three sites along 100 m and 20 m depth contours off the central west coast of India have been estimated using 46 years hindcast-wind-wave data simulated for the Indian Ocean region. The wind waves were simulated with NCEP/NCAR winds as input to a third generation spectral wind wave model. This study showed an increasing trend for the annual mean significant wave heights from south to north ranging between 0.25 and 0.36 cm/year. The wave heights during the southwest monsoon and fair weather periods were observed to have similar trends. The study also showed increasing trends in water depths of 20 m compared to that of 100 m water depth, wherein a maximum increase of 0.22 cm/year is observed.

Global Wave Height Trends and Variability from New Multimission Satellite Altimeter Products, Reanalyses, and Wave Buoys

AbstractLong‐term changes in ocean surface waves are relevant to society and climate research. Significant wave height climatologies and trends over 1992–2017 are intercompared in four recent high‐quality global datasets using a consistent methodology. For two products based on satellite altimetry, including one from the European Space Agency Climate Change Initiative for Sea State, regional differences in mean climatology are linked to low and high sea states. Trends from the altimetry products, and two reanalysis and hindcast datasets, show general similarity in spatial variation and magnitude but with major differences in equatorial regions and the Indian Ocean. Discrepancies between altimetry products likely arise from differences in calibration and quality control. However, multidecadal observations at two buoy stations also highlight issues with wave buoy data, raising questions about their unqualified use, and more fundamentally about uncertainty in all products.

Optimal estimations of directional wave conditions for nearshore field studies

Accurate directional wave conditions at shallow water are crucial for nearshore field studies and necessary as boundary conditions for morphodynamic models. However, obtaining reliable results for all wave parameters can be challenging, particularly regarding wave direction. Here, the accuracy of two global hindcast models and propagation of measured wave conditions using linear wave theory or the SWAN wave model (forced by integrated wave parameters or 2D spectra) is assessed to obtain directional wave conditions at shallow water for Castelldefels beach, northwestern Mediterranean Sea. Results are analyzed using different statistical error parameters and for different wave climates (shore-normal, shore-oblique and bimodal). The analysis shows that global hindcast models correctly predict the trends in wave height and mean wave period but predictions for mean wave direction are only accurate for shore-normal waves. Linear wave theory provides good results for wave height but underestimates refraction, resulting in significant errors in mean wave direction for shore-oblique waves. Finally, SWAN forced with 2D spectra results in the most accurate predictions for all wave parameters. When using integrated wave parameters as boundary conditions, the results for wave height and mean period stay the same whilst the errors in peak period and mean direction worsen for shore-oblique and bimodal wave climates. The reason is that for these wave conditions the directional spectrum constructed out of integrated wave parameters does not resemble the actual directional spectrum.

Comparison of Wind Speed and Wave Height Trends from Twentieth-Century Models and Satellite Altimeters

AbstractThe trends in marine 10-m wind speed U10 and significant wave height Hs found in two century-long reanalyses are compared against a model-only integration. Reanalyses show spurious trends due to the assimilation of an increasing number of observations over time. The comparisons between model and reanalyses show that the areas where the discrepancies in U10 and Hs trends are greatest are also the areas where there is a marked increase in assimilated observations. Large differences in the yearly averages call into question the quality of the observations assimilated by the reanalyses, resulting in unreliable U10 and Hs trends before the 1950s. Four main regions of the world’s oceans are identified where the trends between model and reanalyses deviate strongly. These are the North Atlantic, the North Pacific, the Tasman Sea, and the western South Atlantic. The trends at +24-h lead time are markedly weaker and less correlated with the observation count. A 1985–2010 comparison with an extensive dataset of calibrated satellite altimeters shows contrasting results in Hs trends but similar U10 spatial trend distributions, with general agreement between model, reanalyses, and satellite altimeters on a broad increase in wind speed over the Southern Hemisphere.

Contributions to Coastal Flooding Events in Southeast of Vietnam and their link with Global Mean Sea Level Rise

This work analyzes the components of the total water level (TWL) that cause flooding in a tropical coastal area (Nha Trang beach, Southeast of Vietnam), and examines their link with global mean sea level rise (GMSLR). Interactions between the wave induced run-up (R) and astronomical tide (AT) were responsible for 43% of the 35 flooding events identified between 1993 and 2015. Most of these events (97%) took place during the winter monsoon season, when long-lasting extreme R and positive non-tidal residual (NTR) are likely to occur. Removal of the GMSLR trend from the NTR was found to affect the flood occurrence of 17% of these events, while the trend in wave height did not have any detectable impact. Our research highlights the direct connection between global climate changes and coastal flooding events.

Dynamic Response of Base-Isolated Concrete Rectangular Liquid-Storage Structure Under Large Amplitude Sloshing

AbstractConsidering concrete nonlinearity, the wave height limit between small and large amplitude sloshing is defined based on the Bernoulli equation. Based on Navier-Stokes equations, the mathematical model of large amplitude sloshing is established for a Concrete Rectangle Liquid-Storage Structure (CRLSS). The results show that the seismic response of a CRLSS increases with the increase of seismic intensity. Under different seismic fortification intensities, the change in trend of wave height, wallboard displacement, and stress are the same, but the amplitudes arc not. The areas of stress concentration appear mainly at the connections between the wallboards, and the connections between the wallboard and the bottom.

Detection and Attribution of Climate Change Signal in Ocean Wind Waves

Abstract Surface waves in the ocean respond to variability and changes of climate. Observations and modeling studies indicate trends in wave height over the past decades. Nevertheless, it is currently impossible to discern whether these trends are the result of climate variability or change. The output of an Earth system model (EC-EARTH) produced within phase 5 of the Coupled Model Intercomparison Project (CMIP5) is used here to force a global Wave Model (WAM) in order to study the response of waves to different climate regimes. A control simulation was run to determine the natural (unforced) model variability. A simplified fingerprint approach was used to calculate positive and negative limits of natural variability for wind speed and significant wave height, which were then compared to different (forced) climate regimes over the historical period (1850–2010) and in the future climate change scenario RCP8.5 (2010–2100). Detectable climate change signals were found in the current decade (2010–20) in the North Atlantic, equatorial Pacific, and Southern Ocean. Until the year 2060, climate change signals are detectable in 60% of the global ocean area. The authors show that climate change acts to generate detectable trends in wind speed and significant wave height that exceed the positive and the negative ranges of natural variability in different regions of the ocean. Moreover, in more than 3% of the ocean area, the climate change signal is reversible such that trends exceeded both positive and negative limits of natural variability at different points in time. These changes are attributed to local (due to local wind) and remote (due to swell) factors.

Marine Wind and Wave Height Trends at Different ERA-Interim Forecast Ranges

Abstract Trends in marine wind speed and significant wave height are investigated using the global reanalysis ERA-Interim over the period 1979–2012, based on monthly-mean and monthly-maximum data. Besides the traditional reanalysis, the authors include trends obtained at different forecast range, available up to 10 days ahead. Any model biases that are corrected differently over time are likely to introduce spurious trends of variable magnitude. However, at increased forecast range the model tends to relax, being less affected by assimilation. Still, there is a trade-off between removing the impact of data assimilation at longer forecast range and getting a lower level of uncertainty in the predictions at shorter forecast range. Because of the sheer amount of assimilations made in ERA-Interim, directly and indirectly affecting the data, it is difficult, if not impossible, to distinguish effects imposed by all updates. Here, special emphasis is put on the introduction of wave altimeter data in August 1991, the only type of data directly affecting the wave field. From this, it is shown that areas of higher model bias introduce quite different trends depending on forecast range, most apparent in the North Atlantic and eastern tropical Pacific. Results are compared with 23 in situ measurements, Envisat altimeter winds, and two stand-alone ECMWF operational wave model (EC-WAM) runs with and without wave altimeter assimilation. Here, the 48-h forecast is suggested to be a better candidate for trend estimates of wave height, mainly due to the step change imposed by altimeter observations. Even though wind speed seems less affected by undesirable step changes, the authors believe that the 24–48-h forecast more effectively filters out any unwanted effects.

Summertime wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 62:71-78 (2014) - DOI: https://doi.org/10.3354/cr01260 Summertime wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan Teruhisa Shimada* Graduate School of Science, Tohoku University, Aramaki Aza Aoba 6-3, Aoba-ku, Sendai, Miyagi 980-8578, Japan *Corresponding author: shimada@ocean.caos.tohoku.ac.jp ABSTRACT: Wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan in June–August is investigated using in situ measurements and reanalysis data. The coastal wave height is dominated by the persistent easterly winds induced by the developed Okhotsk high. These winds, which can induce cool summers in northern Japan, favor wave development toward the coast of northern Japan. The wave variability is enhanced along the coast of northern Tohoku by the strong local winds occurring in the lee of Cape Erimo. The results for variability of wave height along the Pacific and Okhotsk Sea coasts of northern Japan are supported by composite analysis of reanalysis wave data. When the Okhotsk high develops and the resulting easterly winds are dominant, the wave height increases near the coast of and to the east of northern Japan. Wave height also increases in the Japan Sea and along the southern coast of Japan, whereas wave height decreases in the Okhotsk Sea. These wave height variations reflect the distinct wind fields associated with the developed Okhotsk high. Trends in wave height are examined using the in situ measurements available for over 20 yr. Only the decreasing trends in the south of northern Japan in August are statistically significant. KEY WORDS: Wave climate · Okhotsk high · Northern Japan · Significant wave height · Cool summer · Yamase Full text in pdf format PreviousCite this article as: Shimada T (2014) Summertime wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan. Clim Res 62:71-78. https://doi.org/10.3354/cr01260 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 62, No. 1. Online publication date: December 02, 2014 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2014 Inter-Research.

Changes in the North Pacific wave climate since the mid‐1990s

AbstractSince the mid‐1990s, ocean wave reanalysis and in situ wave observations have revealed marked downward trends in wave height, exceeding −0.1 m per decade in the midlatitude North Pacific. The wave period in the tropical Pacific is also on a downward trend, exceeding −0.4 s per decade during this period. These changes in wave climate in the Pacific are attributable to recently strengthened trade winds and La Niña‐like conditions in the tropical Pacific. The downward trend in significant wave height in the midlatitude North Pacific is due to strengthening of the negative phase of the Pacific‐North American teleconnection. Numerical experimentations with a wave model also showed that the downward trend in the wave period in the eastern equatorial Pacific was induced not only by increased wind waves due to strengthened trade winds but also by weakened propagating swells from the midlatitude North Pacific.

Historical wave height trends in the South and East China Seas, 1911–2010

AbstractThis study reconstructs 6 hourly significant wave heights (Hs) in the South and East China Seas for the period 1871–2010, using the Twentieth Century Reanalysis ensemble of mean sea level pressure (SLP) fields and a multivariate regression model to represent the Hs‐SLP relationship in each study area. The regression model was calibrated and validated using the ERA‐Interim reanalysis of Hs and SLP for the period 1981–2010. These reconstructions were found to reproduce reasonably well the seasonal mean and maximum Hs climates as represented by the ERA40 and ERA‐Interim wave reanalyses. For each study area, an ensemble of 56 members of 6 hourly Hs was reconstructed for each grid point. The regional mean series of the ensemble mean of the reconstructed consecutive monthly mean Hs was tested for temporal homogeneity, which identified a few discontinuities in the pre‐1946 period and led to the exclusion of the reconstructed Hs for 1871–1910 from trend analysis (due to data uncertainty and inhomogeneity). Each 6 hourly Hs time series for the period 1911–2010 was homogenized for the identified discontinuities, before being used to derive annual and seasonal mean and maximum Hs for trend analysis. The trend analysis results show that, in both study areas, the 1911–2010 wave height trends are dominantly negative, with the exception that the seasonal maximum significant wave heights seem to have increased in summer and spring in the central South China Sea and in summer in the East China Sea.

Estimation of design wave height using empirical simulation technique

In this study, we applied the empirical simulation technique (EST) to the estimation of deepwater design wave heights in several areas in the South Coast of Korea. For the historical typhoons that impacted each area during 59 years from 1951 to 2009, numerical simulations were performed to calculate the wave fields. The simulation results were then used for the generation of the training sets of the EST. The results of the EST were compared with those of the least squares method (LSM) used along with the peaks-over-threshold method. For the 50-year return period wave heights, the EST estimated larger values than the LSM by 2%–26%. If the difference between the EST and the LSM is small for the 50-year return period wave height, the LSM and the EST estimate similar wave heights throughout the return period. If the difference is large, the LSM gives larger wave heights than the EST for relatively short return periods, while the opposite happens for longer return periods. This difference between the EST and the LSM is attributed to the bounce of the relative frequency of wave height at the largest waves (or the occurrence of large wave heights off the increasing trend of wave height with return period).

North Atlantic wave height trends as reconstructed from the 20th century reanalysis

This study reports on the 1871–2010 trends in significant wave heights (Hs) in the North Atlantic, as statistically reconstructed from the 20th century reanalysis (20CR) ensemble of mean sea level pressure (SLP) fields. The 20CR SLP data set for the North Atlantic has been reported to be homogeneous since 1871, although it has discontinuities before 1949 in other regions. A multivariate regression model with lagged dependent variable is used to represent the SLP‐Hsrelationship. It is calibrated and validated using the ERA‐Interim reanalysis ofHsand SLP for the period 1981–2010.Trends in the reconstructed annual mean and maximumHsare found to be consistent with those derived from two dynamical wave reanalysis data sets (MSC50 and ERA40), which indicates robustness of the trend estimates. The trend patterns of extremeHsgenerally feature increases in the northeast North Atlantic with decreases in the mid‐latitudes; but there are seasonal variations. The main features of the patterns of trends over the last half century or so are also seen in the last 140‐yr period (1871–2010). However, the trend magnitudes are much greater in the last half century than in the 140 years.

Present Wave Climate in the Bay of Biscay: Spatiotemporal Variability and Trends from 1958 to 2001

AbstractClimate change impacts on wave conditions can increase the risk of offshore and coastal hazards. The present paper investigates wave climate multidecadal trends and interannual variability in the Bay of Biscay during the past decades (1958–2001). Wave fields are computed with a wave modeling system based on the WAVEWATCH III code and forced by 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) wind fields. It provides both an extended spatiotemporal domain and a refined spatial resolution over the Bay of Biscay. The validation of the wave model is based on 11 buoys, allowing for the use of computed wave fields in the analysis of mean and extreme wave height trends and variability. Wave height, period, and direction are examined for a large array of wave conditions (by seasons, high percentiles of wave heights, different periods). Several trends for recent periods are identified, notably an increase of summer significant wave height, a southerly shift of autumn extreme wave direction, and a northerly shift of spring extreme wave direction. Wave fields exhibit high interannual variability, with a normalized standard deviation of seasonal wave height greater than 15% in wintertime. The relationship with Northern Hemisphere teleconnection patterns is investigated at regional scale, especially along the coast. It highlights a strong correlation between local wave conditions and the North Atlantic Oscillation and the east Atlantic pattern indices. This relationship is further investigated at the local scale with a new method based on bivariate diagrams, allowing the identification of the type of waves (swell, storm, intermediate waves) impacted. These results are discussed in terms of comparison with previous studies and coastal risk implications.