scholarly journals Tropical Cyclone Impacts on Headland Protected Bay

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 190
Author(s):  
Daniel Wishaw ◽  
Javier X. Leon ◽  
Matthew Barnes ◽  
Helen Fairweather
Keyword(s):  
Tropical Cyclone ◽  
Wave Model ◽  
Storm Events ◽  
Shoreline Development ◽  
Sea Levels ◽  
Significant Wave ◽  
Strong Force ◽  
Sediment Volume ◽  
Wave Heights ◽  
Coastal Features

The response of headland protected beaches to storm events is complex and strongly site dependent. In this study, we investigated the response of several headland protected beaches in Noosa, Australia to a tropical cyclone event. Pre and post topographical surveys of all beaches were completed using both pole-mounted RTK-GNSS and structure-from-motion (SfM)-derived elevation models from survey-grade drone imagery to assess sediment volume differentials. Coastal imaging was used to assess shoreline development and identify coastal features while a nearshore wave model (SWAN) was used to project waves into the study site from a regional wave buoy. Obliquely orientated swells drive currents along the headland with sediment being eroded from exposed sites and deposited at a protected site. Elevated sea-levels were shown to be a strong force-multiplier for relatively small significant wave heights, with 10,000 m3 of sediment eroded from a 700 m long beach in 36 h. The SWAN model was adequately calibrated for significant wave height, but refraction of swell around the headland was under-represented by an average of 16.48 degrees. This research has coastal management implications for beaches where development restricts natural shoreline retreat and elevated sea states are likely to become more common.

Wave Probabilities Consistent with Official Tropical Cyclone Forecasts

2016 ◽  
Vol 31 (6) ◽  
pp. 2035-2045 ◽  
Author(s):  
Charles R. Sampson ◽  
James A. Hansen ◽  
Paul A. Wittmann ◽  
John A. Knaff ◽  
Andrea Schumacher
Keyword(s):  
Surface Wave ◽  
Wind Speed ◽  
Tropical Cyclone ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Ocean Surface Wave

Abstract Development of a 12-ft-seas significant wave height ensemble consistent with the official tropical cyclone intensity, track, and wind structure forecasts and their errors from the operational U.S. tropical cyclone forecast centers is described. To generate the significant wave height ensemble, a Monte Carlo wind speed probability algorithm that produces forecast ensemble members is used. These forecast ensemble members, each created from the official forecast and randomly sampled errors from historical official forecast errors, are then created immediately after the official forecast is completed. Of 1000 forecast ensemble members produced by the wind speed algorithm, 128 of them are selected and processed to produce wind input for an ocean surface wave model. The wave model is then run once per realization to produce 128 possible forecasts of significant wave height. Probabilities of significant wave height at critical thresholds can then be computed from the ocean surface wave model–generated significant wave heights. Evaluations of the ensemble are provided in terms of maximum significant wave height and radius of 12-ft significant wave height—two parameters of interest to both U.S. Navy meteorologists and U.S. Navy operators. Ensemble mean errors and biases of maximum significant wave height and radius of 12-ft significant wave height are found to be similar to those of a deterministic version of the same algorithm. Ensemble spreads capture most verifying maximum and radii of 12-ft significant wave heights.

Wave climate change in the Gulf of Bothnia

2021 ◽  
Author(s):  
Jan-Victor Björkqvist ◽  
Jani Särkkä ◽  
Hedi Kanarik ◽  
Laura Tuomi
Keyword(s):  
Climate Change ◽  
Wave Model ◽  
Wave Climate ◽  
Atmospheric Forcing ◽  
Simulation Data ◽  
Significant Wave ◽  
Gulf Of Bothnia ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Projected Changes

<p>Wave climate change in the Gulf of Bothnia in 2030–2059 was investigated using regional wave climate projections. For the simulations we used wave model WAM. As the atmospheric forcing for the wave model we had three global climate scenarios (HADGEM2-ES, MPI-ESM, EC-EARTH) downscaled with RCA4-NEMO regional model. The ice concentration for the wave model was obtained from NEMO ocean model simulations using the same atmospheric forcing. We used both RCP4.5 and RCP8.5 greenhouse gas scenarios. The spatial resolution of the simulation data was 1.8 km, enabling detailed analyses of the wave properties near the coast. From the simulation data we calculated statistics and return levels of significant wave heights using extreme value analysis, and assessed the projected changes in the wave climate in the Gulf of Bothnia. The projected increase in the significant wave heights is mainly due to the decreasing ice cover, especially in the Bothnian Bay. Projected changes in the most prevalent wind direction impacts the spatial pattern of the wave heights in the Bothnian Sea.</p>

Assessing Climate Change in the North Atlantic Wave Regimes

2020 ◽  
Author(s):  
M. Bernardino ◽  
M. Gonçalves ◽  
C. Guedes Soares
Keyword(s):  
System Integration ◽  
Wave Model ◽  
Offshore Structures ◽  
Future Climate ◽  
Wave Direction ◽  
Peak Period ◽  
Significant Wave ◽  
The North ◽  
Wave Heights ◽  
Mean Wave Period

Abstract An improved understanding of the present and future marine climatology is necessary for numerous activities, such as operation of offshore structures, optimization of ship routes and the evaluation of wave energy resources. To produce global wave information, the WW3 wave model was forced with wind and ice-cover data from an RCP8.5 EC-Earth system integration for two 30-year time slices. The first covering the periods from 1980 to 2009 represents the present climate and the second, covering the periods from 2070–2099, represents the climate in the end of the 21st century. Descriptive statistics of wind and wave parameters are obtained for different 30-year time slices. Regarding wind, magnitude and direction will be used. For wave, significant wave height (of total sea and swell), mean wave period, peak period, mean wave direction and energy will be investigated. Changes from present to future climate are evaluated, regarding both mean and extreme events. Maps of the theses statistics are presented. The long-term monthly joint distribution of significant wave heights and peak periods is generated. Changes from present to future climate are assessed, comparing the statistics between time slices.

Consistent Tropical Cyclone Wind and Wave Forecasts for the U.S. Navy

2010 ◽  
Vol 25 (4) ◽  
pp. 1293-1306 ◽  
Author(s):  
Charles R. Sampson ◽  
Paul A. Wittmann ◽  
Hendrik L. Tolman
Keyword(s):  
Tropical Cyclone ◽  
Weather Prediction ◽  
Wave Model ◽  
Tokyo Bay ◽  
Forecast Performance ◽  
Model Driven ◽  
Wave Heights ◽  
Nwp Model ◽  
Forecast Time ◽  
High Seas

Abstract A new algorithm to generate wave heights consistent with tropical cyclone official forecasts from the Joint Typhoon Warning Center (JTWC) has been developed. The process involves generating synthetic observations from the forecast track and the 34-, 50-, and 64-kt wind radii. The JTWC estimate of the radius of maximum winds is used in the algorithm to generate observations for the forecast intensity (wind), and the JTWC-estimated radius of the outermost closed isobar is used to assign observations at the outermost extent of the tropical cyclone circulation. These observations are then interpolated to a high-resolution latitude–longitude grid covering the entire extent of the circulation. Finally, numerical weather prediction (NWP) model fields are obtained for each forecast time, the NWP model forecast tropical cyclone is removed from these fields, and the new JTWC vortex is inserted without blending zones between the vortex and the background. These modified fields are then used as input into a wave model to generate waves consistent with the JTWC forecasts. The algorithm is applied to Typhoon Yagi (2006), in anticipation of which U.S. Navy ships were moved from Tokyo Bay to an area off the southeastern coast of Kyushu. The decision to move (sortie) the ships was based on NWP model-driven long-range wave forecasts that indicated high seas impacting the coast in the vicinity of Tokyo Bay. The sortie decision was made approximately 84 h in advance of the high seas in order to give ships time to steam the approximately 500 n mi to safety. Results from the new algorithm indicate that the high seas would not affect the coast near Tokyo Bay within 84 h. This specific forecast verifies, but altimeter observations show that it does not outperform, the NWP model-driven wave analysis and forecasts for this particular case. Overall, the performance of the new algorithm is dependent on the JTWC tropical cyclone forecast performance, which has generally outperformed those of the NWP model over the last several years.

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.

Equivalent Storm Model for Long-Term Statistics of Sea Storms Off Norway

2018 ◽  
Author(s):  
Valentina Laface ◽  
Anne Karin Magnusson ◽  
Elzbieta M. Bitner-Gregersen ◽  
Magnar Reistad ◽  
Alessandra Romolo ◽  
...  
Keyword(s):  
Spectral Characteristics ◽  
Wave Model ◽  
Significant Wave ◽  
Storm Intensity ◽  
Statistical Equivalence ◽  
Wave Heights ◽  
Model Time Series ◽  
Two Parameters ◽  
Storm Model

The paper deals with long-term analysis of ocean storms off Norway. Sixty years of wave model time series are considered for the analysis. The input data provide spectral characteristics of both wind and swell seas. The availability of global and partitioned significant wave heights enables the possibility of investigating how swell seas influence the storm shape in terms of growing and decay stages and on how this aspect affects the long-term estimates. The analysis is conducted by means of equivalent storm approach which consists of substituting the sequence of actual storms at a given site with a sequence of equivalent storms whose shape is fixed (such as triangular, power or exponential) and then calculating return periods of storm with given characteristics via analytical solutions derived on the basis of storm shape assumed. This is possible due to statistical equivalence between actual and equivalent storms which in turn leads to the equality of wave risk between actual and equivalent storm sequences at a given site. The equivalent storm associated with an actual one is defined by means of two parameters, related to the storm intensity and duration. The equivalent storm intensity is given by the maximum significant wave height in the actual storm history, while the duration is determined via an iterative procedure. In this paper the exponential shape is considered which is referred as equivalent exponential (EES) storm model. Some aspects related with the storm shape and its influence on return values estimate via EES model are investigated. Further, a sensitivity analysis of EES model to the storm threshold is proposed.

scholarly journals Statistical trend analysis and extreme distribution of significant wave height from 1958 to 1999 – an application to the Italian Seas

Ocean Science ◽  
2010 ◽  
Vol 6 (2) ◽  
pp. 525-538 ◽  
Author(s):  
G. Martucci ◽  
S. Carniel ◽  
J. Chiggiato ◽  
M. Sclavo ◽  
P. Lionello ◽  
...  
Keyword(s):  
Extreme Values ◽  
Wave Model ◽  
Northern Adriatic Sea ◽  
Sea State ◽  
Northern Adriatic ◽  
Significant Wave ◽  
Peak Over Threshold ◽  
Wave Heights ◽  
Italian Coasts ◽  
A Site

Abstract. The study is a statistical analysis of sea states timeseries derived using the wave model WAM forced by the ERA-40 dataset in selected areas near the Italian coasts. For the period 1 January 1958 to 31 December 1999 the analysis yields: (i) the existence of a negative trend in the annual- and winter-averaged sea state heights; (ii) the existence of a turning-point in late 80's in the annual-averaged trend of sea state heights at a site in the Northern Adriatic Sea; (iii) the overall absence of a significant trend in the annual-averaged mean durations of sea states over thresholds; (iv) the assessment of the extreme values on a time-scale of thousand years. The analysis uses two methods to obtain samples of extremes from the independent sea states: the r-largest annual maxima and the peak-over-threshold. The two methods show statistical differences in retrieving the return values and more generally in describing the significant wave field. The r-largest annual maxima method provides more reliable predictions of the extreme values especially for small return periods (<100 years). Finally, the study statistically proves the existence of decadal negative trends in the significant wave heights and by this it conveys useful information on the wave climatology of the Italian seas during the second half of the 20th century.

scholarly journals Determination of Significant Wave Heights Using Damping Coefficients of Attenuated GNSS SNR Data from Static and Kinematic Observations

2019 ◽  
Vol 11 (4) ◽  
pp. 409 ◽  
Author(s):  
Ole Roggenbuck ◽  
Jörg Reinking ◽  
Tomke Lambertus
Keyword(s):  
Signal To Noise Ratio ◽  
Wave Model ◽  
Significant Wave ◽  
Sea Surface Roughness ◽  
Wave Heights ◽  
Gnss Reflectometry ◽  
Significant Wave Heights ◽  
Using Data ◽  
Ocean Remote Sensing

Currently, GNSS reflectometry based on the signal-to-noise ratio (SNR) has become an established tool in ocean remote sensing. Here, the distance between an antenna and the water surface is measured by analyzing the oscillation of the SNR observation. Due to the antenna gain pattern, this oscillation is more pronounced for satellite signals coming from low elevation angles. Additionally, the sea surface roughness is related to the attenuation of the SNR oscillation. Hence, the significant wave height (SWH) can be estimated by analyzing the SNR signal. In this work, a method is presented with which the SWH can be calculated from the attenuation’s damping coefficient of the SNR observations measured with surface-based receivers. The method’s usability is demonstrated using data from a static antenna operated in the German Bight and with data from a ship-based antenna. The estimated SWH values were validated against numerical wave model data. For both experiments, a high correlation was found.

scholarly journals Statistical trend analysis and extreme distribution of significant wave height from 1958 to 1999 – an application to the Italian Seas

2009 ◽  
Vol 6 (3) ◽  
pp. 2005-2036 ◽  
Author(s):  
G. Martucci ◽  
S. Carniel ◽  
J. Chiggiato ◽  
M. Sclavo ◽  
P. Lionello ◽  
...  
Keyword(s):  
Extreme Values ◽  
Wave Model ◽  
Northern Adriatic Sea ◽  
Sea State ◽  
Northern Adriatic ◽  
Significant Wave ◽  
Peak Over Threshold ◽  
Wave Heights ◽  
Italian Coasts ◽  
A Site

Abstract. The study is a statistical analysis of sea states timeseries derived using the wave model WAM forced by the ERA-40 dataset in selected areas near the Italian coasts. For the period 1 January 1958 to 31 December 1999 the analysis yields: (i) the existence of a negative trend in the annual- and winter-averaged sea state heights; (ii) the existence of a turning-point in late 70's in the annual-averaged trend of sea state heights at a site in the Northern Adriatic Sea; (iii) the overall absence of a significant trend in the annual-averaged mean durations of sea states over thresholds; (iv) the assessment of the extreme values on a time-scale of thousand years. The analysis uses two methods to obtain samples of extremes from the independent sea states: the r-largest annual maxima and the peak-over-threshold. The two methods show statistical differences in retrieving the return values and more generally in describing the significant wave field. The study shows the existence of decadal negative trends in the significant wave heights and by this it conveys useful information on the wave climatology of the Italian seas during the second half of the 20th century.

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