Tomoya Shimura

Kyoto University | Kyodai · Disaster Prevention Research Institute

Accurate information on waves and storm surges is essential to understand coastal hazards that are expected to increase in view of global warming and rising sea levels. Despite the recent advancement in development and application of large-scale coastal models, nearshore processes are still not sufficiently resolved due to coarse resolutions, trans...

The 2022 Hunga Tonga-Hunga Ha’apai eruption generated tsunamis that propagated across the Pacific Ocean. Along the coast of Japan, nearshore amplification led to amplitudes of nearly 1 m at some locations, with varying peak tsunami occurrence times. The leading tsunami wave can generally be reproduced by Lamb waves, which are a type of air-pressure...

Tropical cyclone is one of the most destructive natural phenomena, causing tremendous disasters worldwide. The maximum intensity of tropical cyclones is determined by momentum and heat transfer at the air-sea interface. Momentum transfer corresponds to the momentum loss of tropical cyclones and, consequently, to the underlying ocean’s momentum gain...

The d4PDF-WaveHs dataset represents the first single model initial-condition large ensemble of historical significant ocean wave height (Hs) at a global scale. It was produced using an advanced statistical model with predictors derived from Japan’s d4PDF ensemble of historical simulations of sea level pressure. d4PDF-WaveHs provides 100 realization...

Historical trends in the direction and magnitude of ocean surface wave height, period, or direction are debated due to diverse data, time-periods, or methodologies. Using a consistent community-driven ensemble of global wave products, we quantify and establish regions with robust trends in global multivariate wave fields between 1980 and 2014. We f...

We analyzed tropical cyclones (TC) based on the theory of Maximum Potential Intensity (MPI) and Maximum Potential Surge (MPS) for a long-term assessment of extreme TC intensity and storm surge heights. We investigated future changes in the MPI fields and MPS for different global warming levels based on 150-year continuous scenario projections (High...

Tropical cyclones (TCs) cause severe coastal flooding in the middle latitudes. While the IPCC Fifth Assessment Reports (AR5, 2013) have focused on mean sea-level rise, recent advances (e.g., IPCC Sixth Assessment Reports, AR6, 2021) have shown the importance of storm surges and wave changes in extreme water levels causing coastal flooding. Both TC...

This study shows how the worst class of typhoons and related storm surge height along major bays in Japan will change based on MPI (Maximum Potential Intensity) theory and MPS (Maximum Potential Storm surge height) model. The climate data used in this study is HighResMIP (High-Resolution Model Intercomparison Project) experiment, which includes hig...

Global estimation of extreme sea levels is required for coast protection. First, 62-year-long historical total sea levels were calculated using an unstructured grid storm surge model and validated against tide gauge data all across the coastlines. Total sea levels were calculated by summing up astronomical tide and storm surge, which were derived s...

New climate experiment was proposed using a model that combines the Meteorological Research Institute's Atmospheric Global Circulation Model (MRI-AGCM) with a slab ocean model to evaluate the impact of warming on tropical cyclones. A month-fixed EA experiment was conducted under the present and future climate under ssp585 scenarios in the climate p...

The number of observations on extreme waves generated by typhoons in the open ocean has been limited. This study conducted the spatial observation of typhoon extreme waves in the open ocean including wave spectra by deploying small GPS-tracked ocean wave buoys recently developed and utilizing the satellite ocean wave data. The typhoon extreme waves...

The individual Drag Force Model (iDFM), a subgrid-scale model that treats groups of buildings in a grid as drag forces, is developed and coupled with the AMR method, in which the computational grid size is refined in time and space, to develop an efficient numerical model of storm surge inundation over metropolis including different scales phenomen...

We conducted a combined probability assessment of earthquake ground motion and tsunami damage for buildings in the entire city of Osaka, considering individual structure types. First, numerous finite fault models were synthetically generated along Nankai Trough. Each fault model has a different slip distribution with similar wavenumber characterist...

This study aims to identify the main factor of sea-level change around Japan. In order to consider climate change that occurs on various temporal and spatial scales, we analyzed three different types of the dataset; tide gauge observation around Japan, sea-level projection by the MIROC6 global climate model (100 km horizontal resolution), and ocean...

Wave response due to topography plays a dominant role in long wave behavior such as tsunamis. Understanding tsunami response functions in real bathymetry can lead to a better prediction of early warning system. This study estimated response functions of tsunamis due to bathymetry, targeting on the Pacific coast of Japan. The estimation method was ba...

Ocean surface wind and wave information is important in a wide variety of areas, such as coastal disaster reduction, offshore structure design, and atmosphere-ocean flux estimation. This study proposed a new method for ocean surface wind estimation from surface wave spectrum information measured by small GPS buoys. The concept of this method relies...

Wave climate is a primary driver of coastal risk, yet how climate change is altering wave climate is not fully understood. Here we identify transitional wave climate regions, coastlines with a future change in the occurrence frequency of a wave climate, with most of the regions located in south-western and eastern ocean basins. Analysis of the spat...

Numerical tsunami inundation simulations using high-resolution (HR) topographical data are important to predict tsunami damage in urban areas at individual building levels accurately but are challenging due to the high computational cost. To address this issue, a subgrid-scale (SGS) model of tsunami inundation, called the individual drag force mode...

This study assesses the effects of internal climate variability on wave height trend assessment using the d4PDF-WaveHs, the first single model initial-condition large ensemble (100-member) of significant wave height (Hs) simulations for the 1951–2010 period, which was produced using sea level pressure taken from Japan’s d4PDF ensemble of historical...

There are numerous global ocean wave reanalysis and hindcast products currently being distributed and used across different scientific fields. However, there is not a consistent dataset that can sample across all existing products based on a standardized framework. Here, we present and describe the first coordinated multi-product ensemble of presen...

Oceania comprises many Small Island Developing States (SIDS), the majority of which are founded on volcanic islands. Small islands are generally vulnerable to the effects of climate change. However, a high number of islands and different coastal morphology make it challenging to accurately estimate climate change impact on this region. Nevertheless...

For coastal adaptation purposes, it is important to estimate the climate related changes in extreme sea levels due to storm surges and ocean waves, in addition to mean sea level rise. This study provides the first consistent and continuous estimation of projected changes in global storm surges and ocean waves from the past to the warmer future, bas...

The parameterization of the sea surface turbulent kinetic energy (TKE) flux due to wave breaking was revisited using the observed data. It is found that the fraction of wave energy taken up into the ocean as sea surface TKE flux depends on the relative angle between wind and wave direction. The fraction tends to be larger under opposite wind condit...

Mangroves are able to attenuate tsunamis, storm surges, and waves. Their protective function against wave disasters is gaining increasing attention as a typical example of the green infrastructure/Eco-DRR (Ecosystem-based Disaster Risk Reduction) in coastal regions. Hydrodynamic models commonly employed additional friction or a drag forcing term to...

Hindcast experiments and pseudo-forecast experiments considering Typhoon Haishen (2020) were conducted using an atmospheric (WRF)-storm surge (GeoClaw) coupled model and a storm surge model with a parametric typhoon model. A series of simulations of the coupled model were used to quantify the error sources of the typhoon track and intensity in the...

The Pacific region consists of numerous Small Island Developing States (SIDS), one of the most vulnerable to flooding caused by compound effects of sea level rise (SLR) and storms. Nevertheless, individual studies regarding the impact assessment for SIDS, such as the low-lying Kiribati, remain scarce. This study assessed the impact of climate chang...

It is becoming important to consider the growth of wind waves due to strong typhoon winds in the bay. However, wave growth in the bay is an intermediate phenomenon hardly modeled by either spectral wave model or phase resolving wave model. Therefore, it is necessary to introduce wind stress terms in the phase resolving wave model that doesn’t usual...

In this study, we examined future changes of explosive cyclones around Japan and their effects on waves along the nation-wide coast using a seamless 150-year high-resolution climate projection from the present to the future climate under warming conditions. The climate projection showed that the number of intense explosive cyclones tends to increas...

The time series prediction of wave height is important for the countermeasure of high wave disaster in the coastal area. Since time series prediction of wave heights over a long recurrence period by dynamical methods is computationally expensive, statistical methods such as neural networks (NN) are considered for prediction. Among the deep learning...

This study conducts numerical tsunami simulations for future Nankai-Tonankai earthquakes and compares the tsunami amplitudes of different earthquake source catalogs along the coastal area of Japan. One of the catalogs is 11 source models proposed by the Central Disaster Management Council (CDMC), the Cabinet Office of Japan. The other is 300 source...

For climate adaptation planning for coastal area, understanding sea level rise on regional-scale is required. We have to assess not only changes in the global averaged sea level but also natural variability in local sea level. In this study, we conducted the analysis of dynamic sea level projection data from the global climate model (MIROC6) and re...

Turbulent mixing in ocean upper layer induces cooling of sea surface temperature (SST) and reductions of heat flux from ocean to typhoon. Sea surface turbulent kinetic energy (TKE) induced by wave dissipation is one of the main source of upper layer turbulence. In this study, two kinds of numerical experiments targeting typhoon Neoguri (2014) have...

Studies on the effects of climate change on waves and storm surges have been widely conducted. In comparison with storm surges, there is a lack of information on the future prediction of waves because of the high computational cost. One of the methods to reduce the computational cost is the statistical wave model. Wind speed and pressure are used a...

In this study, the effects of global warming on tropical cyclones (TCs) were evaluated by using a slab-ocean model coupled with the Atmospheric Global Climate Model (MRI-AGCM) . The warming conditions for the MRI-AGCM climate simulations were obtained from the latest climate models (CMIP6). We have conducted two types of global climate simulations,...

For coastal adaptation purposes, it is important to estimate climate change related future changes in extreme sea levels due to storm surge and ocean waves, in addition to sea level rise. In this study, global storm surge and ocean wave simulations forced by hourly surface winds and pressure from global climate model simulations were conducted. The...

This study proposes and projects the new framework for calculating the climatic Maximum Potential Storm surge height (MPS) based on the typhoon’s Maximum Potential Intensity (MPI) theory for Japan’s major 53 bays. The MPS is optimaized based on dynamic storm surge simulation and is estimate the characteristics of wind-surge for each bay. We analyze...

Understanding the systematic characteristics of tropical cyclones (TCs) represented in the Global Climate Model (GCM) is important for reliable climate change impact assessments. The atmospheric GCM (AGCM) and ocean wave models were coupled by incorporating the wave-dependent momentum flux. Systematic impacts of wave-dependent momentum flux on TC c...

We provide a comprehensive analysis of the spatial-temporal changes in the atmospheric-driven major wave climates (easterlies, southerlies, and westerlies) under two different Representative Concentration Pathways, the RCP2.6 and RCP8.5 scenarios for the end-of-the-century (2075–2099). By comparing the projected scenarios with historical conditions...

Extreme surface ocean waves are often primary drivers of coastal flooding and erosion over various time scales. Hence, understanding future changes in extreme wave events owing to global warming is of socio-economic and environmental significance. However, our current knowledge of potential changes in high-frequency (defined here as having return p...

This paper presents a multivariate classification of the global wave climate into types driven by atmospheric circulation patterns. The primary source of the net long-term variability is evaluated based on historical wave simulations. Results show that the monsoon, extratropical, subtropical, and polar wave climate types of the Pacific and North At...

Unmanned aerial vehicles (UAVs), represented by rotor-based drones, are suitable for volcanic observations owing to the advantages of mobility and safety. In this study, vertical profiles of wind and aerosol concentrations at altitudes up to 1000 m around Mt. Sakurajima, one of the most active volcanoes in Japan, were measured in situ using a drone...

This study developed an integrated model for the long-term assessment of extreme storm surge heights based on the maximum potential intensity (MPI) of a tropical cyclone, which is used to conduct future climatological projections of maximum potential storm surge height (MPS). We apply the MPS method to three major bays in Japan, Tokyo, Osaka, and N...

Climate change due to global warming is expected to have major impacts on phenomena such as tropical cyclones (TCs), Baiu, precipitation, and seasonal storms. Many natural disasters in East Asia are driven by TC (typhoon) activity in particular and their associated hazards are sensitive to local-scale characteristics. As such, it is critically impo...

A Correction to this paper has been published: https://doi.org/10.1007/s10584-021-03023-1

Issues related to climate change in coastal areas have been addressed in a wide variety of academic fields and societies, including meteorology, marine physics, chemistry, biology, ecology, policy science, and economics. However, the efforts and initiatives of each relevant academic field or society are rarely shared because climate change science...

The compounding effects of storm surges and sea level rise (SLR) are expected to accelerate coastal hazards and inundation. Therefore, projecting the compound effects in coastal territories is important for impact assessments and adaptation. Small island states in the South Pacific are one of the areas that are the most highly impacted by climate c...

Future projections of ocean wave climate related with global warming has been conducted for the assessment of climate change impacts on coastal disaster, beach morphology, and coastal structure design. In this study, we conduct the high-resolution future wave climate projection in the East Asia region and detail analysis on wave climate based on tw...

Projecting the sea level rise (SLR), storm surges, and related inundation in the Pacific Islands due to climate change is important for assessing the impact of climate change on coastal regions as well as the adaptation of the coastal regions. The compounding effects of storm surges and SLR are one of the major causes of flooding and extreme events...

Climatology of tropical cyclone (TC) intensity produced by global climate model (GCM) is important for climate change assessment. The available energy of a tropical cyclone is determined by the conditions of the environment around TC. Particularly, the sea surface temperature (SST) is an important factor in TC intensity. In this study, we have deve...

Coastal structures should be designed to consider to future sea level rise due to climate change. However, the projection of regional sea level change is different from the global mean projection and shows complex spatial patterns caused by thermosteric change and dynamic change associated with ocean circulation. This study analyzed the long-term s...

Although the frequency of tropical cyclones shows a declining trend around the world, the intensity will increase, and the occurrence possibilities of higher waves and severer storm surges are also increasing. In a changing global environment, a stage which stochastically assume by scientific basis has come, rather than repeating unexpected damage...

Plain Language Summary Climate change is one of the main issues of sustainable development. The projection of climate change is important for assessment of impact on our environment, and the global climate model is used for the climate change projection. Accurate knowledge of momentum, heat, and carbon transfer at the atmosphere‐ocean interface, so...

This dataset, produced through the Coordinated Ocean Wave Climate Project (COWCLIP) phase 2, represents the first coordinated multivariate ensemble of 21st Century global wind-wave climate projections available (henceforth COWCLIP2.0). COWCLIP2.0 comprises general and extreme statistics of significant wave height (HS), mean wave period (Tm), and me...

This is a review paper on the community ensemble estimation of the maximum storm surge heights in the three major bays of Tokyo Bay, Osaka Bay and Ise Bay in Japan. The published papers from the Journal of Japan Society of Civil Engineers since 1990 are reviewed and the maximum storm surge heights are summarized for the present climate and the futu...

Typhoon climatology estimated by global climate model is important for impact assessment of climate change. We developed wave-coupled global atmospheric climate model and conducted a set of typhoon simulation with sea surface drag coefficient considering wave age and misalignment of wave-wind direction. A set of typhoon simulation was targeted to t...

Understanding the reliability of Global Climate Models (GCMs) to reproduce the historical surface wind fields is integral part of building robust projections of surface wind-climate, and other wind-dependent geophysical climatic variables. Understanding the skill of atmosphere-only models (AGCM), coupled atmosphere-ocean models (AOGCM) and fully-co...

Understanding climate-driven impacts on the multivariate global wind-wave climate is paramount to effective offshore/coastal climate adaptation planning. However, the use of single-method ensembles and variations arising from different methodologies has resulted in unquantified uncertainty amongst existing global wave climate projections. Here, ass...

A 34-year high-resolution ocean surface wave climate hindcast around Japan is presented, and the wave climate around Japan is examined from a spectral point of view. The spectral wave model is forced by the sea surface wind data obtained from the JRA-55 atmospheric reanalysis. The wave climate hindcast is validated by comparing it with buoy observa...

This study examines long-term ensemble projections for historical and future climate conditions over 5,000 years using an atmospheric global circulation model. The future climate condition is assumed as a constant +4°C in the global mean temperature from before the Industrial Revolution (c.a. 1850), and the historical climate condition is perturbed...

Hurricanes Irma and Maria caused catastrophic damages across the Caribbean Islands during the 2017 hurricane season. After the storms, a joint United States–Japanese team investigated coastal impacts in the US Virgin Islands, which are composed of the islands of St. Thomas, St. John, Water Island, and St. Croix. Coastal inundation was dominated by...

Sea level rise and wave characteristics change under climate change have been reported, and the impact assessments due to theses change have been carried out by several researchers. In general the beach profile change on climate change is simulated using Bruun rule only considering sea level rise. However the wave characteristics change is importan...

Future projection of wave climate around Japan using high resolution wave model was conducted. Climatology of significant wave heights and mean wave periods around Japan would be decreased in the future climate by 10% and 3%, respectively. Temporal average of wave spectra was analyzed in addition to the bulk wave parameters. Energy decreases all ov...

Wave-induced turbulent kinetic energy (TKE) plays an important role on the numerical simulation of sea surface mixing. This study has been conducted to improve the parameterization of sea surface turbulent energy fluxes induced by white-capping based on the observation data. The data indicates that TKE fluxes coefficient α proposed by Feddersen and...

Using high-resolution numerical weather prediction model and coupled storm surges and waves, we conducted pseudo-prediction experiments on the maximum wind speed, maximum storm surge height, and maximum wave height for 2018 Typhoon Jebi. The central pressure and maximum wind speed of the typhoon become more accurate as the forecasting time length b...

The study conducted a series of storm surge and wave simulations caused by Typhoon Jebi using a parametric wind and pressure field model, and mesoscale atmospheric model WRF to hindcast observed storm surges and waves in Osaka Bay. Appropriate typhoon radiuses and the limit of wind speed for wave depending sea surface drag coefficient were examined...

The extreme value analysis of wave height has been used to estimate design value of coastal structures. Generally, the extreme wave heights are obtained based on the observations or hindcasts, simply. However, the influence of the weather systems on the extreme value distribution is not taken into consideration. This study analyzes statistical chara...

A tropical cyclone (TC) dataset has been created for the d4PDF climate dataset. It contains 11,400 years of TC tracks (historic and future), which makes it possible to estimate 100 year or longer return values. The detection method uses wind speed and pressure difference threshold parameters and is tuned to optimize annual TC count and genesis lati...

The contribution of bubbles to the air-ocean heat exchange during passages of extreme typhoons was investigated based on a field observation at the ocean. We proposed an ultrasonic backscatter model estimating bubble population and heat flux through the bubble interface. Bubbles produced in an extreme weather were found to be entrained to an ocean su...