Variational Wave Research Articles

Machine Learning for Nonorographic Gravity Waves in a Climate Model

Abstract There is growing use of machine learning algorithms to replicate subgrid parameterization schemes in global climate models. Parameterizations rely on approximations; thus, there is potential for machine learning to aid improvements. In this study, a neural network is used to mimic the behavior of the nonorographic gravity wave scheme used in the Met Office climate model, important for stratospheric climate and variability. The neural network is found to require only two of the six inputs used by the parameterization scheme, suggesting the potential for greater efficiency in this scheme. Use of a one-dimensional mechanistic model is advocated, allowing neural network hyperparameters to be chosen based on emergent features of the coupled system with minimal computational cost, and providing a testbed prior to coupling to a climate model. A climate model simulation, using the neural network in place of the existing parameterization scheme, is found to accurately generate a quasi-biennial oscillation of the tropical stratospheric winds, and correctly simulate the nonorographic gravity wave variability associated with El Niño–Southern Oscillation and stratospheric polar vortex variability. These internal sources of variability are essential for providing seasonal forecast skill, and the gravity wave forcing associated with them is reproduced without explicit training for these patterns. Significance Statement Climate simulations are required for providing advice to government, industry, and society regarding the expected climate on time scales of months to decades. Machine learning has the potential to improve the representation of some sources of variability in climate models that are too small to be directly simulated by the model. This study demonstrates that a neural network can simulate the variability due to atmospheric gravity waves that is associated with El Niño–Southern Oscillation and with the tropical and polar regions of the stratosphere. These details are important for a model to produce more accurate predictions of regional climate.

Using long-range transmissions in the Beaufort Gyre to test the sound-speed equation at high pressure and low temperature.

An ocean acoustic tomography array with a radius of 150 km was deployed in the central Beaufort Gyre during 2016-2017 for the Canada Basin Acoustic Propagation Experiment. Five 250-Hz transceivers were deployed in a pentagon, with a sixth transceiver at the center. A long vertical receiving array was located northwest of the central mooring. Travel-time anomalies for refracted-surface-reflected acoustic ray paths were calculated relative to travel times computed for a range-dependent sound-speed field from in situ temperature and salinity observations. Travel-time inversions for the three-dimensional sound-speed field consistent with the uncertainties in travel time [∼2 ms root mean square (rms)], receiver and source positions (∼ 3 m rms), and sound speed calculated from conductivity-temperature-depth casts could not be obtained without introducing a deep sound-speed bias (below 1000 m). Because of the precise nature of the travel-time observations with low mesoscale and internal wave variability, the conclusion is that the internationally accepted sound-speed equation (TEOS-10) gives values at high pressure (greater than 1000 m) and low temperature (less than 0 °C) that are too high by 0.14-0.16 m s-1.

Aortic pulse wave comparison between controls and triathletes in baseline conditions and in response to acute maximum exercise

To determine the effects of intense training on aortic pulse wave variables and hemodynamic parameters at baseline and at recovery from maximal exercise testing (MaxET) in triathletes compared with sedentary individuals. In this prospective and experimental study, 21 triathletes and 21 sedentary individuals were recruited and evaluated prior and two minutes after the MaxET using the Mobil-O-Graph®, which estimates the aortic pulse wave from the brachial artery pressure. The augmentation index (AIx@75) was lower in triathletes after the MaxET compared to control group (16.34 ± 5.95 vs. 23.5 ± 8.53%, p = 0.001), while the pulse wave velocity (PWV) was similar between groups. The heart rate was significantly lower at baseline and after MaxET in triathletes group (55.70 ± 8.95 bpm 91.49 ± 11.39 bpm) compared with control group (62.11 ± 6.70 bpm; 102.08 ± 10.85 bpm). The stroke volume was significantly higher at baseline (96.08 ± 13.96 ml; 86.17 ± 11.24 ml) and after MaxET in triathletes group (69.15 ± 6.51 ml, 58.38 ± 6.99 ml) compared with control group. Triathetes show lower value of AIx@75 after MaxET in comparison with the control group. AIx@75, in addition to being an indirect measure of arterial stiffness, is also a measure of left ventricular afterload. Thus, the lower AIx@75 in triathletes may be due to their lower left ventricular afterload, lower myocardial oxygen demand, and greater coronary perfusion than sedentary individuals. The hemodynamic changes observed in triathletes at rest and during an acute exercise bout are distinctive characteristics of aerobic physical training.

On global wave height climatology and trends from multiplatform altimeter measurements and wave hindcast

Reliable estimates of ocean surface waves and their long-term global trends are fundamentally important for numerous ocean engineering and geophysical applications. Nonetheless, it is scientifically and technically demanding to accurately identify such relatively small trends [O(0.1−1) cm yr−1] from wave data currently available. In 2022, Young and Ribal demonstrated that by changing the calibration method, multiplatform altimeter observations yield noticeable differences in wave height estimates and their trends. In this paper, we use our global wave hindcast as a baseline and confirm that observations calibrated relative to one another (i.e., “altimeter-altimeter” calibration) ultimately outperform traditionally “altimeter-buoy” calibrated data. The former leads to more consistent mean and extreme wave heights across simultaneously operating altimeters and consequently to a more homogeneous evolution of global sea states over the past several decades. The underlying reason is hypothesized to be that temporal inhomogeneities in long-term NDBC buoy records due to changes in buoy hardware and software over time introduce comparable inhomogeneities to long-term altimeter observations when the “altimeter-buoy” calibration is adopted. It is encouraging to observe that the global trends of mean and 90th-percentile wave heights over the period 1992-2019 from our hindcast and re-calibrated altimeter data are very close: approximately 0.3 cm yr−1. Nonetheless, the altimeter-based trend of 99th-percentile wave height, Hs99, is substantially-but-spuriously stronger mainly due to markedly growing availability of altimeter missions over time. Our work clearly demonstrates the power of third generation spectral wave models as diagnostics tools. Given the uncertainties embedded in buoy and satellite observations, wave modeling and global wave hindcasts can indeed guide these measurements. Further analysis of the underlying climate physics driving the interannual variability of ocean waves in wind-sea dominated regions is also presented.

Spatial and temporal variability in mode-1 and mode-2 internal solitary waves from MODIS-Terra sun glint off the Amazon shelf

Abstract. The Amazon shelf is a key region for intense internal tides (ITs) and nonlinear internal solitary wave (ISWs) generation associated with them. The region shows well-marked seasonal variability (from March to July, MAMJJ, and from August to December, ASOND) of the circulation and stratification, which can both induce changes in the ISW physical characteristics. The description of the seasonal and neap–spring tidal variability in the ISWs off the Amazon shelf is performed for the first time using a meaningful data set composed of 140 MODIS-Terra imagery from 2005 to 2021, where about 500 ISW signatures were identified in the sun glint region. Previous studies have documented the existence of mode-1 ISWs, but the region appears as a newly described hotspot for mode-2 ISWs. ISW packets separated by typical mode-1 (95–170 km; 2.1–3.8 m s−1) and mode-2 (46–85 km; 1.0–1.9 m s−1) IT wavelengths have been identified and mapped coming from different IT generation sites. For each ISW, a group of waves (3 to 10) is generally follows the largest crest. The intra-packet distance between each wave in the group is about 10 to 20 km. Regions of higher occurrence of ISWs are spaced by a IT mode-1 wavelength. We make the assumption that it might correspond to the IT reflection beams at the surface, which may generate newer ISWs. The mean mode-1 and mode-2 inter-packet distances do not show significant differences according to their IT generation sites. The ISW activity is higher (more than 60 % of signatures) during spring tides than neap tides. In the region under the influence of the North Equatorial Counter Current (NECC), ISWs are separated by a mean mode-1 IT wavelength which is 14.3 % higher during ASOND than during MAMJJ due to a deeper thermocline and the reinforcement of the NECC. These ISWs are also characterized by a wider inter-packet distance distribution (higher standard deviation) that may be related to the stronger eddy kinetic energy (EKE) during ASOND compared to MAMJJ. The mean inter-packet distance of mode-2 ISWs remains almost unchanged during the two seasons, but the inter-packet distance distribution is wider in ASOND than in MAMJJ as for mode 1. Note that these results need to be treated with caution, as only few occurrences of mode-2 waves were found during MAMJJ. In the region of the NECC, the direction of propagation for all modes is very similar in MAMJJ (about 30∘ clockwise from the north), whereas, for ASOND, the ISWs propagate in a wider pathway (from 0 to 60∘ clockwise from the north), due to a much larger eddy activity. During ASOND, as the background flux goes further east, the inter-packet distances become larger (4 % for mode 1 and 7.8 % for mode 2). These results show that the reinforcement of the NECC in ASOND appears to play a role in diverting the waves towards the east, increasing their phase velocities and their eastern traveling direction component when compared to MAMJJ. Calculations of the IT velocities using the Taylor–Goldstein equation supported our results regarding the presence of ISWs associated with mode-2 ITs and additionally the IT seasonal variability.

Korean Wave in Indonesia: Are there any changes in perception and intention to visit Korea?

South Korea has a good image overseas due to the success of its national branding. With the Korean Wave as their national branding, Koreans introduce their country and culture through Korean entertainment. Indonesia is one of the Asian countries exposed to the Korean Wave, especially Korean dramas. This paper aims to analyze the determinants of changes in perceptions and the desire of Indonesians to visit South Korea as a tourist destination. International strategy theory, international marketing theory, and Korean Wave types are analyzed. The research sample consists of 237 randomly selected Korean Wave fans and non-fans. Data were collected using a questionnaire adapted and modified from previous studies. Respondents received questionnaires on-line via Google Forms. Multiple linear regression analysis was used in this study. The findings show that international strategy and marketing can adequately explain changes in the perception and desire of Indonesians to visit South Korea as a tourist destination. The Korean Wave has a positive and significant effect on changes in public perceptions toward Korea. The significant level of 0.000 <0.05 concludes that the four Korean Wave variables (Korean music, food, dramas, and products)simultaneously have a positive effect on changes in the perception of Indonesians people toward South Korea. However, K-pop and K-food were not found to determine the intention to visit South Korea as a tourist destination.

On the G'/G Expansion Method Applied to (2+1)-Dimensional Asymmetric-Nizhnik-Novikov-Veselov Equation

In this paper, the G'/G expansion method is applied to the (2+1)-dimensional Asymmetric-Nizhnik-Novikov-Veselov equation (ANNV). The motivation is creating new families of solitary waves. The system of equations has been combined in one partial differential equation (PDE) and the traveling wave variable has been applied to transform the resultant equation into an ordinary differential equation (ODE). The homogenous balance condition has been applied to determine the truncation variable of the G'/G expansion. Four cases are created according to the appropriate choice of the arbitrary constants relations. For each case, some new solitary wave solutions including solitons and kinks represented by trigonometric, hyperbolic, logarithmic, polynomial, and combinations of these functions.

Upsampling wave temporal resolution: Investigating wave parameters and the influence on WEC power performance

Power production of wave energy converters (WEC) predicted in the time domain utilize wave resource parameters and time-domain hydrodynamic model simulations of the WEC. While the hydrodynamic model provides high temporal resolution of power production (10’s of Hz), the wave resource parameters are often based on frequency-domain calculations with temporal resolution of 30 minutes to an hour. However, real ocean wave conditions vary on much shorter time scales. Relying on frequency-domain calculations will not be sufficient to capture the short-term variability and accurately predict WEC power production for a standardized methodology that follows power system requirements. These requirements need forecasted data with high sampling frequency for accurate energy predictions. Looking specifically at resource characterization, high temporal resolution datasets are not publicly available or do not exist for many coastal locations. Due to data availability, low temporal resolution datasets are being used in a majority of studies to generate representative wave conditions as inputs to numerical simulations. Representative wave conditions are used to generate wave spectrums. The issue with this practice is spectrums are then used to predict the efficiency of systems that will not accurately capture the variability of waves in short timeframes. Creating a standardized methodology to increase the temporal resolution of metaocean conditions to inform model development can provide better forecasting of power production. Random amplitude, Fourier coefficient methods have been suggested for WEC simulations of finite durations to improve the observed variability in wave heights and power production. Variability using this method does increase for finite durations compared to the commonly used deterministic amplitude method. In this paper we will investigate the influence of wave parameters (significant wave height, maximum wave height, and energy period) on the prediction of WEC power production. A better understanding of the influence of these parameters will provide a path towards future standardization methodology for resource inputs for time-domain modeling.

CONTRIBUTION OF INFRAGRAVITY WAVES TO STORM WATER LEVEL ALONG A LARGE INLET: IMPLICATIONS FOR FLOODING AND OVERTOPPING HAZARDS

Tidal inlets are transitional area between the ocean and an estuary or a lagoon. They are characterised by very complex hydro-morphodynamics processes, resulting from the interaction between tidal currents and waves with large and rapid water level changes. The coastline around the inner part of the inlet and more generally the entire lagoon often host important economic and touristic activities. In these environments, the studies of hazards associated with energetic events are mainly based on modelling approaches. However, the phase-averaged numerical models typically used for large-scale coastal applications exclude infragravity waves (long waves ranging from several tens of seconds to several minutes, noted hereinafter IG) and phase-resolving model are too computationally expensive for such large domains. Therefore, the propagation of waves from the open sea to the lagoon and in particular the characterisation of IG waves are still poorly understood (Bertin et al., 2018). To study the amplitude and spatial variability of IG waves in the Arcachon lagoon during storms, the Xbeach model (Roelvink et al., 2009) was implemented in surfbeat mode (SB mode).

An Investigation of the Cumulative Effects of Depressive Symptoms on the Cognitive Function in Community-Dwelling Older Adults: Analysis of the Korean Longitudinal Study of Aging

This study investigated the cumulative effects of depressive symptoms on cognitive function over time in community-dwelling older adults. Data were investigated from 2,533 community-dwelling older adults who participated in the Korean Longitudinal Study of Aging (KLoSA) from the 5th (2014) to the 8th wave (2020). The association between cumulative depressive symptoms and cognitive function was identified through multiple regression analysis. When the multiple regression analysis was conducted from each wave, the current depressive symptoms scores and cognitive function scores were negatively associated, regardless of the waves (B5th = -0.26, B6th = -0.26, B7th = -0.26, and B8th = -0.27; all p < .001). Further, when all the previous depressive symptoms scores were added as explanatory variables in the 8th wave, the current one (B8th = -0.09, p < .001) and the previous ones (B5th = -0.11, B6th = -0.09, and B7th = -0.13; all p < .001) were also negatively associated with the cognitive function score. The delta R², which indicates the difference between the model's R² with and without the depressive symptoms scores, was greater in the model with all the previous and current depressive symptoms scores (6.4%) than in the model with only the current depressive symptoms score (3.6%). Depressive symptoms in older adults have a long-term impact. This results in an accumulated adverse effect on the cognitive function. Therefore, to prevent cognitive decline in older adults, we suggest detecting their depressive symptoms early and providing continuous intervention to reduce exposure to long-term depressive symptoms.

Long-term trends and wave climate variability in the South Atlantic Ocean: The influence of climate indices

Linking wave climate variability and trends with climate indices is important to better understand and predict large-scale patterns of wave variability down to wave conditions at the coast. This study investigates such links in the South Atlantic Ocean using 72 years of ERA5 wave hindcast. Different wave parameters are computed, including storm wave statistics, and are further analyzed in terms of long-term trends and interannual changes. Our results indicate that, over the last decades, wave height has been significantly increasing across the entire domain, while extreme events statistics are also increasing, although with more complex spatial variability. The variations of these wave properties are primarily correlated, from low to high latitudes, with the Atlantic Multidecadal Oscillation (AMO), Tropical Southern Atlantic Index (TSA) and Southern Annular Mode (SAM), with different preferred timescales. We think that better understanding and predicting the evolution of these climate indices, including under climate change, will be critical to anticipate coastal hazards in this region.

PASS: A scoring system to evaluate persistent kidney injury in critically ill ICU adult patients

Background: We evaluated if the course of recovery from sepsis-induced acute kidney injury (AKI) can be predicted using variables collected at admission. Methods: A total of 63 patients admitted for sepsis-induced AKI in our Mangalore ICU were evaluated and baseline demographic and clinical/laboratory parameters, including serum creatinine (SCr), base excess (BE), Plethysmographic Variability Index (PVI), Caval Index, R wave variability index (RVI), mean arterial pressure (MAP) and renal resistivity index (RI) using renal doppler and need for inotropes were assessed on admission. Patients were managed as per standard protocol. After six hours of fluid resuscitation, patients were classified as volume responders or non-responders. Re-assessment was done at 24 hours and 72 hours after admission. Primary outcome was persistent AKI after 72 hours. Secondary outcome was initiation of dialysis or death within 15 days of admission. Results: A total of 34 subjects recovered from AKI, of whom 32 patients were volume responders and 31 were non-responders. Response to fluid, MAP at admission and six hours, BE at admission, inotrope requirement, and PVI at admission did not correlate with recovery. Multiple logistic regression showed that SCr &lt; 2.36 mg%, RVI &gt; 14.45 and RI &lt; 0.8 on admission correlated with recovery and they were evaluated further to model AKI recovery and develop PASS. PASS score = (SCr points × 5.4) + (RVI points × 4.0) + (RI points × 6.2). One point each was allotted if SCr was &lt; 2.36, RVI was &gt; 14.45 and RI was &lt;0.8, and 0 otherwise. A score &gt; 7.8 predicted recovery with a sensitivity of 79.4%, specificity of 72.4%, PPV 81.8%, NPV 76.7% and AuROC of 0.85. Conclusions: The PASS score can be used to identify salvageable cases of sepsis-AKI, guiding fluid resuscitation and aiding early referral from rural to tertiary care centers for better management.

Impact of seasonal variability of sea waves on the dynamics of a predator–prey system

Impact of seasonal variability of sea waves on the dynamics of a predator–prey system

PENGARUH KOREAN WAVE TERHADAP KEPUTUSAN PEMBELIAN PADA ALBUM OFFICIAL K-POP GIRL GROUP BLACKPINK DI KABUPATEN GARUT

The purpose of this study is to measure how influential the Korean Wave variables are on purchasing decisions on the official k-pop girl group BLACKPINK's album. The method used in this study is a causal method using a quantitative approach. By taking the population in Garut Regency where there are special requirements, namely having to be a kpopers and who have listened to music or songs from BLACKPINK and taking a sample of 100 respondents. And for the validity test and reliability test this can be used in research, as well as the normality test used in research has substantial significance. The Korean Wave variable has a considerable impact on purchasing decisions, according to the direct correlation test. Based on this direct regression test, the purchasing decision variable is positively influenced by the Korean Wave variable. In addition, the Korean Wave simultaneously has a positive and significant influence on purchasing decisions, as shown by the F statistical test between the independent factors and the dependent variable. Keywords : BLACKPINK, Korean Wave, Buying Decision, K-Pop, Album Official

Conservation laws of the complex Ginzburg-Landau equation

The complex Ginzburg-Landau equation is considered. It is shown that there are three conservation laws corresponding to this equation. These conservation laws are found using the direct transformation of the equation. The first integral of the ordinary differential equation is given by reduction to the traveling wave variables. The bright optical soliton of the Ginzburg-Landau equation is found. Conservative quantities corresponding to the power, momentum and energy of optical soliton are calculated.

CIPS Observations of Gravity Wave Activity at the Edge of the Polar Vortices and Coupling to the Ionosphere

AbstractA new Cloud Imaging and Particle Size (CIPS) gravity wave (GW) variance data set is available that facilitates automated analysis of GWs entering the mesosphere. This work examines several years of CIPS GW variances from 50 to 55 km in the context of the Arctic and Antarctic polar vortices. CIPS observes highest GW activity in the vortex edge region where horizontal wind speeds are largest, consistent with previously published GW climatologies in the stratosphere and mesosphere. CIPS observes the well‐documented planetary wave (PW)‐1 patterns in GW activity in both hemispheres. In the Northern Hemisphere, maximum GW activity occurs over the North Atlantic and western Europe. In the Southern Hemisphere, maximum GW activity stretches from the Andes over the South Atlantic and Indian Oceans, as expected. In the NH, CIPS GW spatial patterns are highly correlated with horizontal wind speed. In the SH, CIPS GW patterns are less positively correlated with the winds due to increased zonal symmetry and orographic forcing. The Andes Mountains and Antarctic Peninsula, South Georgia Island, Kerguelen/Heard Islands, New Zealand, and Tasmania are persistent sources of orographic GWs. Atmospheric Infrared sounder observations of stratospheric GWs are analyzed alongside CIPS to explore vertical GW coherence and to infer GW propagation and sources. NH midlatitude GW activity is reduced during the January 2021 SSW, as expected. This reduction in GWs leads to a simultaneous reduction in traveling ionospheric disturbances (TIDs), providing more evidence that weak polar vortex events with weak GW activity leads to reduced daytime TID activity.

Numerical investigation on a floating self-reacting resonant wave energy converter

A self-reacting resonant C-shaped wave energy converter (SR-C-WEC) consisting of a pair of resonant sub-C-WECs connected by a rigid frame is proposed, which uses the two sub-C-WECs to provide mutual reaction force to solve the efficiency problem caused by floating WECs being hard to provide enough reaction force on WEC and uses the controllable resonant WEC to solve the efficiency problem caused by the temporal variability of waves. Resonant control and equivalent wave force control models are proposed to maximize the absorbed power. The effect of spacing between two sub-C-WECs, natural period, PTO damping and mooring stiffness to absorbed power is investigated. It is found that SR-C-WEC can achieve resonance at each wave condition and the power generation is maximum when the spacing is equal to half wavelength, which is comparable to the power generation when the frame is fixed. In a real sea condition, when the spacing is adjusted or not, the difference in average annual power is only 8.3%. Therefore, constant spacing can be used to simplify the structure and facilitate the application of SR-C-WEC. It is predicted that SR-C-WEC can reach 3638 effective power generation hours per year in real seas off China.

Cylinder water entry on a perturbed water surface

The perturbations existing on a breaking wavefront can be a potential explanation for the slamming pressure variability in wave impacts. Here, we investigate the effect of these perturbations by forced vertical slamming of a two-dimensional circular cylinder with constant downward velocity on standing waves. Through experimental modelling and numerical simulation, the slamming force is measured for several standing wave amplitudes and wavelengths. The standing wave phase is tuned such that the impact occurs symmetrically at the instant of maximum crest or trough. Our observations show that slamming coefficients vary with the standing wave amplitude when the wavelength is kept constant and vice versa. The trough impact slamming coefficient can be more than two times the flat impact, and up to four times the crest impact. The experimental results are reproduced by numerical simulations and they agree reasonably well in general. Two analytical approaches based on the von Kármán (NACA, vol. 321, 1929, pp. 1–8) and Wagner (Z. Angew. Math. Mech., vol. 12, 1932, pp. 913–215) methods, which consider the effect of water surface curvature, are introduced. The slamming coefficient calculated from these methods can provide a bound in which the slamming coefficient can be found for each standing wave amplitude and wavelength. Further insight is achieved by numerical simulations of impact on the shorter wavelength to diameter ratio of$0.05&lt;\lambda /D&lt;0.4$. As the wavelength to diameter ratio becomes smaller, the cylinder impacts the water surface at several locations. As a result, multiple peaks occur, and the trapped air at different locations between the cylinder and the water surface yields oscillations with different frequencies on the slamming coefficient time history.

Development and Application of an Infragravity Wave (InWave) Driver to Simulate Nearshore Processes

AbstractInfragravity waves are key components of the hydro‐sedimentary processes in coastal areas, especially during extreme storms. Accurate modeling of coastal erosion and breaching requires consideration of the effects of infragravity waves. Here, we present InWave, a new infragravity wave driver of the Coupled Ocean‐Atmopshere‐Waves‐Sediment Transport (COAWST) modeling system. InWave computes the spatial and temporal variation of wave energy at the wave group scale and the associated incoming bound infragravity wave. Wave group‐varying forces drive free infragravity wave growth and propagation within the hydrodynamic model of the coupled modeling system, which is the Regional Ocean Modeling System (ROMS) in this work. Since ROMS is a three‐dimensional model, this coupling allows for the combined formation of undertow currents and infragravity waves. We verified the coupled InWave‐ROMS with one idealized test case, one laboratory experiment, and one field experiment. The coupled modeling system correctly reproduced the propagation of gravity wave energy with acceptable numerical dissipation. It also captured the transfer of energy from the gravity band to the infragravity band, and within the different infragravity bands in the surf zone, the measured three‐dimensional flow structure, and dune morphological evolution satisfactorily. The idealized case demonstrated that the infragravity wave variance depends on the directional resolution and horizontal grid resolution, which are known challenges with the approach taken here. The addition of InWave to COAWST enables novel investigation of nearshore hydro‐sedimentary dynamics driven by infragravity waves using the strengths of the other modeling components, namely the three‐dimensional nature of ROMS and the sediment transport routines.

Analysis of the 20-Year Variability of Ocean Wave Hazards in the Northwest Pacific

In the Northwest Pacific (NWP), where a unique monsoon climate exists and where both typhoons and extratropical storms occur frequently, hazardous waves pose a significant risk to maritime safety. To analyze the 20-year variability of hazardous waves in this region, this study utilized hourly reanalysis data from the ECMWF ERA5 dataset covering the period from 2001–2020, alongside the wave risk assessment method. The ERA5 data exhibits better consistency, in both the temporal and spatial dimensions, than satellite data. Although hazardous wind seas occur more frequently than hazardous swells, swells make hazardous waves travel further. Notably, the extreme wave height (EWH) shows an increasing trend in high- and low-latitude areas of the NWP. The change in meridional wind speeds is the primary reason for the change in the total wind speed in the NWP. Notably, the maximum annual increase rate of 0.013 m/year for EWH exists in the region of the Japanese Archipelago. This study elucidated the distributions of wave height intensity and wave risk levels, noting that the EWHs of the 50-year and 100-year return periods can reach 20.92 m and 23.07 m, respectively.