Tomoki Ushiyama

• Ph.D
• Senior Researcher at Public Works Research Institute

Against extensive adoption of transgenic crops assessments of transgene flow is essential to prevent its contamination to other cultivars and to protect biodiversity. For the purpose of developing improved numerical model to predict gene flow on anemophilous plants, we predict pollen dispersal and hybridization between two rice cultivars (Oryza sat...

Providing quantitative information on expected flood damage due to climate change is essential for minimizing the future risk through climate change adaptation and mitigation measures. Understanding changes in flood damage in the future due to climate change impact considering regional or local characteristics is also crucial for better manage floo...

Study region: Lower Kelani River Basin, Sri Lanka. Study focus: The dynamics of human-flood interactions are particularly pronounced in flood-prone regions. Effective flood management requires a synergistic approach that combines "hard" with "soft" measures in these areas. However, a gap remains in the empirical evaluation of the combined efficie...

The diurnal rainfall cycle is a key factor affecting tropical precipitation variability. However, the diurnal cycle is not sufficiently represented in numerical models, which can be associated with convective parameterization in the models. This study presents the sensitivity of simulated precipitation over Java Island, Indonesia, to adjusting two...

Understanding the impacts of climate change and conversion of paddy field areas in the future on agricultural production is an essential part of flood‐risk management. However, the quantitative impact of flood on agricultural crops in the far‐future under climate change, considering prospective changes in paddy area, is still not clearly understand...

In this study, an ensemble inflow-prediction system was developed for a hydropower-generation dam in the upper Sai River basin, and the accuracy of ensemble inflow prediction, which is important for efficient dam operation, was investigated. First, the Water and Energy Based Distributed Hydrological Model for Snow (WEB-DHM-S), a hydrological model...

Se presenta el diseño de un pronóstico hidrológico probabilístico a partir de ensambles de modelos de Predicción Numérica Meteorológica (NWP). El caso de estudio se centra en la predicción de niveles hidrométricos correspondientes a un evento de inundación repentina ocurrido en octubre de 2019 en la cuenca Sarandí-Santo Domingo, provincia de Buenos...

Urban flooding, particularly in vulnerable basins such as the Suquía River in Córdoba, Argentina, poses a significant threat due to intense and sudden rainfall combined with the basin's steep and expansive area. In response, the PREVENIR project, initiated in 2022, aims to develop an early warning system (EWS) to mitigate the impacts of heavy rainf...

This study presents the advances in ensemble flood forecasting for the upper Suquía River Basin, part of the PREVENIR project initiated in 2022. Utilizing two high-resolution numerical weather prediction (NWP) models, Weather Research and Forecasting (WRF) and Scalable Computing for Advanced Library and Environment (SCALE), we generated ensemble fo...

Extreme rainfall or heavy rainfall events (HREs) causes significant socio-economic damages annually affecting local development especially in developing countries. Thus, assessing changes in frequency and magnitude of HREs under climate change using global climate model (GCM) projections became ubiquitous to hydrological impact studies. Here, we pr...

Understanding the effects of climate change on agricultural crops is an essential part of flood-risk management and adaptation measures. However, the quantitative impact of flood damage on agricultural crops under climate change is still not clearly understood. It is thus crucial to investigate flood damage to agricultural crops under climate chang...

Floods and landslides caused by extreme weather events, such as localized excessive rainfall in Japan, cause enormous devastation. Multicell clouds, on the other hand, have a common duration of over an hour and greater aerial coverage than single-cell clouds. For flood warning systems to function properly, the hazardous cloud must be detected quick...

Heavy rainfall due to tropical cyclones (TCs) in the North Indian Ocean (NIO) adversely impacts nations frequently. Though extensive research has focused on TCs in the NIO, less attention has been given to the connection between TCs and extreme events in Sri Lanka. This study examined atmospheric characteristics during sixteen extreme events, focus...

Urban floods and intense precipitation are highly destructive natural disasters. In the context of climate change, it is imperative to undertake novel measures for mitigating their impact on vulnerable communities. The PREVENIR initiative has started in 2022, with the objective of developing an early warning system centered on the impacts caused by...

Flood early warning systems (FEWS) are crucial for flood risk management; however, several catchments in the developing world are still far behind in all aspects of FEWS and thus, they encounter devastating damage recurrently due to limitations in data, knowledge, and technologies. This paper presents a catchment-scale integrated flood information...

Enhancing flood resilience, including the development of social capacity and early warning systems, in addition to structural measures, is one of the key solutions to mitigating flood damage, which will be more intensified in the future due to climate change. This study was conducted to develop a comprehensive methodology for enhancing flood resili...

Three months long ensemble inflow prediction was newly introduced to the operation support system for a single hydroelectric dam developed by Koike et.al.(2021). Inflow predictions; 39 hours ensemble and three months ensemble, were confirmed to have meaningful accuracy and adopted to reservoir operations. The system showed that the reservoir’s auth...

This research conducted ensemble inflow simulations for electric power generation dams in the Sai River in Japan. After developing the Water and Energy Based Distributed Hydrological Model 4 components for Snow (WEB-DHM-4cS), we validated the model by conducting hydrological simulations for three consecutives years from August 2015 to July 2018 and...

We developed an operation support system for a single hydroelectric dam using ensemble flood prediction to reduce water-related disaster risks intensified by climate change and increase renewable energy generation promoted by the Carbon Neutral policy. The system was experimentally applied to dam operation simulations for warm seasons of two consec...

We report experimental observations of precipitable water vapor (PWV) derived using Global Positioning System/Global Navigation Satellite System (GPS/GNSS) receivers mounted on autonomous surface vehicles (ASVs), which were deployed in the tropical Pacific Ocean from July to September 2018. The GPS atmospheric delay was estimated by precise point p...

In October 2019, Typhoon Hagibis traveled over eastern Kanto area, provided record-breaking rainfall in the wide area of Kanto and Tohoku regions, resulted in severe flood disasters including Chikuma River. We applied our ensemble flood forecasting method for Chikuma River flood event to investigate the predictability of our system. Our method cons...

Atmospheric numerical simulation models play a very important role for understanding dispersion and deposition processes of radioactive materials. Dispersion and deposition process of radioactive materials emitted from the Fukushima Daiichi nuclear power plant after the nuclear accident accompanied the great Tohoku earthquake and tsunami on 11 Marc...

Flood forecasting in a transboundary river basin is challenging due to insufficient data sharing between countries in the upper and lower reaches of a basin. A solution is the use of satellite-observed rainfall and numerical weather prediction (NWP) for hydrological forecasting. We applied this method to the transboundary sparsely gauged Chenab Riv...

Recent advances in regional ensemble weather prediction systems (EPS) can considerably improve the prediction of torrential rainfall and resulting severe floods with a longer lead time. To maximize this advantage, we developed an ensemble flood forecasting system, composed of an ensemble Kalman filter and a regional numerical weather prediction on...

Mountain snowpack and its distribution both have intimate connections to regional hydrology by preserving winter precipitation to sustain streamflows during the summer months. One of the key knowledge gaps in mountainous region is the interplay of precipitation and temperature with changing altitudes. Three‐dimensional temperature distribution is p...

This study focused on flood damage assessment for future floods under the impact of climate change. Four river basins of Southeast Asia were selected for the study. They included the Pampanga River Basin (PRB) in the Philippines, the Solo River Basin (SRB) in Indonesia, the Lower Mekong River Basin (LMRB) in Cambodia and Vietnam, and the Chao Phray...

Based on the atmospheric turbulence diffusion model, a three-dimensional numerical model was applied for predicting the cross-pollination rate distribution in leeward area of windbreaks by considering actual weather observation data, daily fluctuation parameter of pollen release rate, pollen life during flowering period, etc. Several cases of cross...

In the summer of 2016, 14 cases of jumping cirrus (JC) were observed around the Kanto region in Japan by ground-based, visible-light cameras. The cameras were set at the summit of Mt. Fuji and National Defense Academy (Kanagawa, Japan), and 15-second time-lapse photography was continually taken for the period. The location and spatial scale of the...

We developed a regional ensemble prediction system to support advanced dam operation including predischarge of dam water for the purpose of reducing flood risk and effective water resource management, simultaneously. The targets were Ooigawa and upper Saigawa Basin. The prediction experiment was performed during July to September in 2015 to 2017. T...

In this study, we analyzed and evaluated the methods to understand the uncertainty of the precipitation prediction by climate change among different precipitation models. Representative Concentration Pathways 8.5 (2075-2099) future climate characteristics in Vietnam has been chosen with four best-scored CMIP5 General Circulation Models (GCMs) on DI...

In fact, this is an abstract related to the poster presentation exhibited during the EGU2017 General Assembly. It was thought of as a staring point of a new bilateral project (just before submission of its draft) involving Japan and Czechia. The main purpose of this project is the flood risk reduction using different remote sensing products (satell...

Because of recent advances in numerical weather prediction (NWP), flood forecasting coupled with NWP has become beneficial in some suitable conditions. Such advances include computing power development, improved weather observations using satellite sensors, improved data assimilation techniques, and ensemble prediction systems accounting for foreca...

As many water related disasters occur frequently around the world, proper assessment of future climate change impact on floods and droughts is essential. In this study, we focused on basin-scale climate change impact assessment as necessary information for studying adaptation measures on the basis of integrated water resources management. We used M...

To understand future inundation patterns due to climate change, temporal-spatial flood inundation in the Pampanga River basin was analyzed. Dynamic downscaling by the WRF model and bias correction using ground rainfall were applied to the results from MRI-AGCM3.2S with the RCP 8.5 scenario to prepare rainfall data in future climate. Inundation anal...

Recent advances of regional ensemble weather predictions could improve the prediction of torrential rainfall and resulted severe floods with a longer lead time. To realize this goal, we have developed an ensemble flood forecasting system, composed of an ensemble Kalman filter and a regional numerical weather prediction model in atmospheric part, an...

In order to be able to issue flood warnings not hours but days in advance, numerical weather prediction (NWP) is essential to the forecasting of flood-producing rainfall. The regional ensemble prediction system (EPS), advanced NWP on a local scale, has a high potential to improve flod forecasting through the quantitative prediction of precipitation...

The Pampanga River Basin in Philippines suffers from floods due to typhoons or monsoonal rainfall every year. Assessment of changes in flood risk due to global warming is, therefore, an important issue for this flood-vulnerable basin. We studied possible changes in rainfall features under present (1979–2003) and future (2075–2099) climates using dy...

Recent advances of regional ensemble weather predictions have increasingly improved predictability of rainfall forecasts, which would be useful for streamflow forecasts. We have developed an ensemble flood forecasting system, composed of an ensemble Kalman filter and regional model WRF (Weather Research and Forecasting) in atmospheric part, and Rai...

The change of climatic patterns is a major concern in the Pampanga River basin, the Philippines, and may intensify the magnitude of drought and flood hazard events under climate change uncertainty. Most of municipal water demand requirements for the Metro Manila relies on the Angat dam, which drains only 546 km2 at the headwaters of the Pampanga Ri...

Lagged ensemble forecasting of rainfall and rainfall-runoff-inundation (RRI) forecasting were applied to the devastating flood in the Kabul River basin, the first strike of the 2010 Pakistan flood. The forecasts were performed using the Global Forecast System of the National Centers for Environmental Prediction (NCEP-GFS) and were provided four tim...

With the increase of extreme climate events due to the global climate change, urban areas have been becoming more prone to flooding. This trend highlights the importance of effective schemes to mitigate the damage and loss due to inundation. The advancement of numerical prediction method for heavy rainfall is a key technology for early warning. The...

Heavy rains and urban floods are an important global issue under the context of climate change. Since the current effects of climate change, new strategies to mitigate the impact in vulnerable communities must be done. In this framework, the PREVENIR project is being implemented since 2022 for five years. The main goal of this project is to develo...

Recent development of a rainfall-runoff-inundation (RRI) model allows simultaneous simulation of river discharges and flood inundations in large river basins. Because of the structural simplicity with fast computation, the model is suitable for flood risk mapping with climate change projections. To meet the objective, however, it is necessary to te...

Torrential rainfall events often brought sudden flood and damages especially in urban area. However, it is still hard to forecast the occurrence of torrential rainfall. In this study we analyzed evolution process of a torrential rainfall event that was occurred at Itabashi, Tokyo, on July 5, 2010, to accumulate knowledge of developing mechanism and...

X-band multi parameter (MP) radar network has an advantage in accuracy of quantitative rainfall estimation (QPE) by dual polarization parameters. However, it has an disadvantage in detecting area by considerable signal attenuation by rain particles. Therefore, combined use of both kind of radars would be anticipated. In this study, we developed an...

Pakistan suffered from a devastating flood disaster in 2010. This study investigated the potential of utilizing a rainfall-runoff-inundation (RRI) model for providing useful information for effective emergency response. The model was applied to the entire Indus River Basin (modeled area: 929,723 km2 with 60 sec. (about 1.7 km) grid-cells, and its p...

Windbreak nets and plant windbreaks are effective in suppressing maize pollen dispersal and cross-pollination. This paper seeks effective arrangements of windbreak nets or plant windbreaks to suppress cross-pollination from a 50 m square maize donor plot. A pair of numerical models, the A2Cflow and A2Ctd, which had previously validated the pollen d...

With the extensive adoption of transgenic crops, an understanding of transgene flow is essential to manage gene flow to non-GM crops. Thus, a flexible and accurate numerical model is required to assess gene flow through pollen dispersal. A three-dimensional atmospheric model combined with a diffusion transport model would be a useful tool for predi...

A field observational campaign [i.e., the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO)] was conducted over the central equatorial Indian Ocean in October–December 2006. During MISMO, large-scale organized convection associated with a weak Madden–Julian oscillation (MJO) broke out, and some other notable variations wer...

Windbreaks or shelterbelts have been used for centuries for reducing wind speed and improving microclimate and environment, and increasing crop yields due to windbreak not only can affect the airflow around it but also affect the microclimates through the interaction of the airflow with the exchanges of heat and water vapor. However, systematic stu...

For the extensive adoption of transgenic crops in recent years, an assess-ment of transgene flow is essential to prevent the contamination of other related species and to protect biodiversity. A 3-D prognostic atmospheric model and a diffusion transport mod-el predicted gene flow through pollen dispersal and cross-pollination between two adjacent m...

To sustain a stable food supply without losses from various hazards, such as insects, diseases, or abnormal climate conditions induced by global change, application of genetically modified (GM) organ-isms is one potential tool for agriculture. However, GM crops do not exist in traditional agricultural environments; thus, the risks resulting from th...

The role of air–sea interaction in the diurnal variations of convective activity during the suppressed and developing stages of an intraseasonal convective event is analyzed using in situ observations from the Mirai Indian Ocean cruise for the Study of the Madden–Julian oscillation (MJO)-convection Onset (MISMO) experiment. For the whole period, co...

Windbreak nets are most often used to prevent agricultural wind damage, since they are cheap and easy to install. However, little is provided concerning the dynamical characteristics of such windbreak nets, hampering the design of windbreak planning through the quantitative use of the latter. We measured both dynamical characteristics and wind fiel...

We used a three-year dataset from an impact disdrometer to study the diurnal to interannual variation of the raindrop size distribution (DSD) over Palau in the Western Pacific warm pool. The DSD variability was primarily seasonal, with a secondary contribution due to the El Niño Southern Oscillation (ENSO) cycle. We did not find evidence of a diurn...

The present paper investigates the relationship between the skin sea surface temperature (SSTskin) and the precipitable water (PW) observed over the tropical Indian Ocean. PW is derived from a shipborne Global Positioning System (GPS). Composite diurnal variations indicate that the increase of PW and radar echo coverage (rainfall) in the daytime co...

A procedure to correct the reflectivity data from multiple radars is proposed. The TRMM/PR (Tropical Rainfall Measurement Mission satellite/Precipitation Radar) is used as the standard calibrator. The data from a disdrometer is also used to account for the effects of rain attenuation at short wavelengths. The procedure is evaluated in the case of o...

1] This paper describes the structure and evolution of northward propagating mesoscale convective systems (MCSs) observed over the tropical western Pacific on 15 June 2005. A wedge-shaped convective cloud area, consisting of three groups of MCSs, was generated near the equator to the north of New Guinea at around 0000 LST on 15 June, and one of the...

Surface heat fluxes around 2°N, 138°E in the tropical western Pacific have been acquired by Research Vessel (R/V) Mirai for a total of 74 days during four observational periods. Significant fractions of the sensible and latent heat fluxes are found to occur during occasional passages of precipitating cloud systems which cause large surface fluxes....

The Mirai Indian Ocean cruise for the Study of the Madden–Julian oscillation (MJO)-convection Onset (MISMO) was a field experiment that took place in the central equatorial Indian Ocean during October–December 2006, using the research vessel Mirai, a moored buoy array, and land-based sites at the Maldive Islands. The aim of MISMO was to capture atm...

The effect of the assimilation of dropsonde data over the tropical western Pacific was investigated in an objective analysis. In June 2005, 30 dropsondes were released on four separate flight days. The data impact was assessed using the objective analysis dataset of “ALERA.” The analysis of the zonal wind field over the tropical western Pacific in...

Satellite imagery and C-band radar on the R/V Mirai detected an isolated convective cloud band over the western tropical Pacific, and dropsondes observed the surrounding atmospheric environment. The reasonable development mechanism of this unusual cloud band is investigated using observational and numerical simulation data. Although theoretically,...

The structures of deep convections and their environment were examined during the latter half of the active phase of the Madden-Julian oscillation (MJO), using fine temporal resolution of research vessel observation data. During the intensive observation period, the MJO associated with deep convections passed through the observation area. A strong...

Diurnal variation of precipitation was investigated over Palau in the tropical western Pacific. Compared to other larger islands, heating effect of the island is assumed to be small in Peleliu Island. Peleliu Island was chosen for the representative of oceanic feature. Over Palau region, the season can be divided into westerly and easterly wind reg...

In this study, the authors focused on the seasonal variations of precipitation properties over the western Pacific, particularly those associated with the wind direction of the monsoon. An observational project over Peleliu Island in the Republic of Palau was carried out, and data on precipitation, equivalent cloud amount, and precipitable water we...

Dual-Doppler radar system is a unique instrument to detect the three-dimensional structure of cloud systems includ-ing the rain particle distribution and their movement. In the real observation of cloud systems using dual-Doppler radars, researchers have to choose a variety of options, such as time of collecting three-dimensional volumes or interva...

Dual Doppler radar observations were carried out from November 1992 to January 1993 during the TOGA-COARE IOP (Tropical Ocean and Global Atmosphere-Coupled Ocean Atmosphere Response Experiment, Intensive Observation Phase) at Manus Island in Papua New Guinea. The heating profiles of six stratiform and eight convective cloud systems were calculated...

Observations of tropical convection and cloud clusters with two X-band Doppler radars were carried out on Manus Island, Papua New Guinea for two and a half months from 12 November 1992 during the Intensive Observation Period (TOP) of the TOGA-COARE. Several different types of clouds were observed by Doppler radars during the period, such as squall...

We examine the relationship between mesoscale rainfalls and large-scale atmospheric fields in the western Pacific using data obtained in the TOGA-COARE IOP (Tropical Ocean and Global Atmosphere-Coupled Ocean Atmosphere Research Experiment, Intensive Observation Phase). The data used for our analysis were a two-months period of successive x-band rad...