HIGH RESOLUTION WAVE CLIMATE HINDCAST AROUND JAPAN BASED ON JRA-55 AND ANALYSIS ON WAVE SPECTRUM CLIMATE

2018 ◽  
Vol 74 (2) ◽  
pp. I_127-I_132
Author(s):  
Tomoya SHIMURA ◽  
Nobuhito MORI
Keyword(s):  
High Resolution ◽  
Wave Spectrum ◽  
Wave Climate

Covariate Extreme Value Analysis Using Wave Spectral Partitioning

2020 ◽  
Vol 37 (5) ◽  
pp. 873-888 ◽  
Author(s):  
Jesús Portilla-Yandún ◽  
Edwin Jácome
Keyword(s):  
Extreme Values ◽  
Wind Waves ◽  
Spectral Energy Distribution ◽  
Wave Spectrum ◽  
Wave Climate ◽  
Extreme Value ◽  
Extreme Value Analysis ◽  
Spectral Energy ◽  
Value Analysis ◽  
Spectral Partitioning

AbstractAn important requirement in extreme value analysis (EVA) is for the working variable to be identically distributed. However, this is typically not the case in wind waves, because energy components with different origins belong to separate data populations, with different statistical properties. Although this information is available in the wave spectrum, the working variable in EVA is typically the total significant wave height Hs, a parameter that does not contain information of the spectral energy distribution, and therefore does not fulfill this requirement. To gain insight in this aspect, we develop here a covariate EVA application based on spectral partitioning. We observe that in general the total Hs is inappropriate for EVA, leading to potential over- or underestimation of the projected extremes. This is illustrated with three representative cases under significantly different wave climate conditions. It is shown that the covariate analysis provides a meaningful understanding of the individual behavior of the wave components, in regard to the consequences for projecting extreme values.

A 39-year high resolution wave hindcast for the Chinese coast: Model validation and wave climate analysis

2019 ◽  
Vol 183 ◽  
pp. 224-235 ◽  
Author(s):  
Jian Shi ◽  
Jinhai Zheng ◽  
Chi Zhang ◽  
Antoine Joly ◽  
Wei Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Model Validation ◽  
Wave Climate ◽  
Wave Hindcast ◽  
Chinese Coast ◽  
Climate Analysis

scholarly journals The Influence of the Spectral Truncation on the Simulation of Waves in the Tropical Stratosphere

2015 ◽  
Vol 72 (10) ◽  
pp. 3819-3828 ◽  
Author(s):  
T. R. Krismer ◽  
M. A. Giorgetta ◽  
J. S. von Storch ◽  
I. Fast
Keyword(s):  
High Resolution ◽  
Lower Stratosphere ◽  
Wave Spectrum ◽  
Atmospheric Model ◽  
Quasi Biennial Oscillation ◽  
Highly Active ◽  
Main Driver ◽  
Resolution Model ◽  
Diffusion Scheme ◽  
Tropical Wave

Abstract Convectively triggered waves are the main driver of the tropical stratospheric circulation. In atmospheric models, the model’s resolution limits the length of the simulated wave spectrum. In this study, the authors compare the tropical tropospheric wave sources, their projection on the wave field in the lower stratosphere, and the circumstances of their upward propagation in the atmospheric model ECHAM6 with three spectral truncations of T63, T127, and T255. The model internally generates the quasi-biennial oscillation (QBO), which dominates the variability in the tropical stratosphere. This analysis focuses on two opposite phases of the QBO to account for the influence of the background wind field on the wave filtering. It is shown that, compared to the high-resolution model versions, the T63 version has less convective variability and less wave momentum in the lower stratosphere at wavenumbers larger than 20, well below the version’s truncation limit. In the low-resolution version, the upward propagation of the waves is further hindered by the highly active (relative to the high-resolution versions) horizontal diffusion scheme. However, even in the T255 version of ECHAM6, the convective variability is too small compared to TRMM observations at periods shorter than 2 days and wavelengths shorter than 1000 km. Hence, to model a realistic tropical wave activity, the convective parameterization of the model has to improve to increase the day-to-day precipitation variability.

scholarly journals A Multimodal Wave Spectrum–Based Approach for Statistical Downscaling of Local Wave Climate

2017 ◽  
Vol 47 (2) ◽  
pp. 375-386 ◽  
Author(s):  
C. A. Hegermiller ◽  
J. A. A. Antolinez ◽  
A. Rueda ◽  
P. Camus ◽  
J. Perez ◽  
...  
Keyword(s):  
Statistical Downscaling ◽  
Wave Spectrum ◽  
Wave Climate ◽  
Ocean Basin ◽  
Coastal Hazards ◽  
Wave Spectra ◽  
Bulk Wave ◽  
Wave Parameters ◽  
Local Wave ◽  
Wave Conditions

AbstractCharacterization of wave climate by bulk wave parameters is insufficient for many coastal studies, including those focused on assessing coastal hazards and long-term wave climate influences on coastal evolution. This issue is particularly relevant for studies using statistical downscaling of atmospheric fields to local wave conditions, which are often multimodal in large ocean basins (e.g., Pacific Ocean). Swell may be generated in vastly different wave generation regions, yielding complex wave spectra that are inadequately represented by a single set of bulk wave parameters. Furthermore, the relationship between atmospheric systems and local wave conditions is complicated by variations in arrival time of wave groups from different parts of the basin. Here, this study addresses these two challenges by improving upon the spatiotemporal definition of the atmospheric predictor used in the statistical downscaling of local wave climate. The improved methodology separates the local wave spectrum into “wave families,” defined by spectral peaks and discrete generation regions, and relates atmospheric conditions in distant regions of the ocean basin to local wave conditions by incorporating travel times computed from effective energy flux across the ocean basin. When applied to locations with multimodal wave spectra, including Southern California and Trujillo, Peru, the new methodology improves the ability of the statistical model to project significant wave height, peak period, and direction for each wave family, retaining more information from the full wave spectrum. This work is the base of statistical downscaling by weather types, which has recently been applied to coastal flooding and morphodynamic applications.

scholarly journals Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

2018 ◽  
Vol 11 (1) ◽  
pp. 215-232 ◽  
Author(s):  
Catrin I. Meyer ◽  
Manfred Ern ◽  
Lars Hoffmann ◽  
Quang Thai Trinh ◽  
M. Joan Alexander
Keyword(s):  
High Resolution ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Wave Spectrum ◽  
Horizontal Resolution ◽  
Wave Activity ◽  
Large Variability ◽  
Wave Event ◽  
The Waves

Abstract. We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a statistical basis. The complete HIRDLS measurement period from January 2005 to March 2008 is covered. The seasonal and latitudinal distributions of gravity wave activity as observed by AIRS and HIRDLS agree well. A strong annual cycle at mid- and high latitudes is found in time series of gravity wave variances at 42 km, which has its maxima during wintertime and its minima during summertime. The variability is largest during austral wintertime at 60∘ S. Variations in the zonal winds at 2.5 hPa are associated with large variability in gravity wave variances. Altogether, gravity wave variances of AIRS and HIRDLS are complementary to each other. Large parts of the gravity wave spectrum are covered by joint observations. This opens up fascinating vistas for future gravity wave research.

Projected Changes in the Occurrence of Extreme and Rogue Waves in Future Climate in the North Atlantic

2017 ◽  
Author(s):  
Odin Gramstad ◽  
Elzbieta Bitner-Gregersen ◽  
Erik Vanem
Keyword(s):  
North Atlantic ◽  
Wave Spectrum ◽  
Wave Model ◽  
Rogue Waves ◽  
Wave Climate ◽  
Future Climate ◽  
The North ◽  
Wave Parameters ◽  
The Future ◽  
The North Atlantic

We investigate the future wave climate in the North Atlantic with respect to extreme events as well as on wave parameters that have previously not been considered in much details in the perspective of wave climate change, such as those associated with occurrence of rogue waves. A number of future wave projections is obtained by running the third generation wave model WAM with wind input derived from several global circulation models. In each case the wave model has been run for the 30-year historical period 1971–2000 and the future period 2071–2100 assuming the two different future climate scenarios RCP 4.5 and RCP 8.5. The wave model runs have been carried out by the Norwegian Meteorological Institute in Bergen, and the climate model result are taken from The Coupled Model Intercomparison Project phase 5 - CMIP5. In addition to the standard wave parameters such as significant wave height and peak period the wave model runs provided the full two-dimensional wave spectrum. This has enabled the study of a larger set of wave parameters. The focus of the present study is the projected future changes in occurrence of extreme sea states and extreme and rogue waves. The investigations are limited to parameters related to this in a few selected locations in the North Atlantic. Our results show that there are large uncertainties in many of the parameters considered in this study, and in many cases the different climate models and different model scenarios provide contradicting results with respect to the predicted change from past to future climate. There are, however, some situations for which a clearer tendency is observed.

Wave climate in the Black Sea: description and trend evaluation using new ECMWF-ERA5 reanalysis and wave-current interaction.

2021 ◽  
Author(s):  
Salvatore Causio ◽  
Piero Lionello ◽  
Stefania Angela Ciliberti ◽  
Giovanni Coppini
Keyword(s):  
Black Sea ◽  
Wave Spectrum ◽  
Atmospheric Stability ◽  
Wave Model ◽  
Wave Climate ◽  
The Black Sea ◽  
Wave Direction ◽  
Wave Regime ◽  
Sea Temperature ◽  
Discrete Interaction

<p>This study analyzes the evolution of the wave climate in the Black Sea basin in a 31-year long hindcast (1988-2018) performed with the third-generation wave model WaveWatchIII v5.16, forced by the ECMWF-ERA5 reanalysis winds at 30km of spatial resolution and 1-hour frequency. The wave model is implemented on a grid covering the whole Black Sea, with 3km grid step and is off-line coupled with a NEMO based hydrodynamical model. The wave spectrum is discretized using 24 directional sectors, and 30 frequencies, with 10% increment starting from 0.055Hz. The model is implemented to solve deep water processes, following the WAM Cycle4 model physics, with Ultimate Quickest propagation scheme and GSE alleviation, which is implemented in WWIII. Wind input and dissipation are based on Ardhuin et al. (2010), wave-wave interactions are based on Discrete Interaction Approximation. Currents and air-sea temperature difference are provided to the wave model to account for Doppler shift and atmospheric stability above the sea. Model validation and statistical analysis have been carried out to describe the wave climate of the Black sea, considering the following wave fields: significant wave height (Hs), mean wave period (Tm) and mean wave direction. Statistics as Mean, Maximum, 5<sup>th</sup> percentile and 95<sup>th</sup> statistics have been computed to produce monthly climatologies. The work considers also the evaluation of trends for Hs and Tm, and the evaluation of tendency in the occurrence frequency of mean and max fields for Hs and Tm.</p><p>There is no evidence about an overall trend in Hs and Tm, but tendencies can be highlighted in some months and seasons. The most evident trend occurs in Summer on the whole wave spectrum, with reduction of Hs and Tm in the Eastern basin, and increasing in the South-Western basins. Even the evaluation of occurrence frequencies suggests that Black Sea is subjected to a change in the wave regime.</p>

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