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本稿では初めに、2011年東北津波直後に政府や学会から提示された津波対策の基本方針を解説し、次に、各種津波対策を実現するための第一歩となる、津波強度(ハザード)を工学的に評価する津波ハザード評価手法を解説し、また、これら評価の不確定性を陽に取り扱う確率論的津波ハザード評価手法(PTHA: Probabilistic Tsunami Hazard Analysis)の概要を述べ、最後に、PTHAの最新の研究成果について紹介する。確率論的ハザード評価は、津波の現象に限らず、災害を引き起こす様々な自然現象を想定する際の不確定性を明示する有効な手法であり、今後の災害対策を推進するうえで、重要な概念である。

We calculated the ground deformation due to differently shaped rotational ellipsoidal pressure sources beneath the Aira caldera using a FEM model. Deeper horizontal pressure sources seem to be consistent with the observed data, as well as that expected from the Mogi pressure source. However, the variation of residual sum of square is small to decide a certain oblateness value of horizontal pressure sources.

We obtain a three-dimensional seismic velocity structure below the Aira caldera at a depth shallower than 45km, southwest Japan, applying seismic tomography inversion method to analyze 16, 110 P-wave onsets and 11, 838 S-wave onsets of natural earthquakes observed by 45 seismic stations, and 3, 121 P-wave onsets generated by artificial explosions. An anomalous zone of low S-wave velocity is discriminated at depths from 12 km to 22 km below the center of the Aira caldera. The High Vp/Vs zone below SW part of Sakurajima at a depth of 35 km may be related to the occurrence of deep low-frequency earthquakes.

The localized heavy rainfall induced by the single-cell could be more hazardous if the single-cell merged into the multicell thunderstorms. Flash floods and landslides are common disasters with a lifespan of multicell more than one hour and a scale of an area larger than a single-cell. To mitigate the flood risk, the short-term precipitation forecast is suggested as one of the observation tools to disseminate early warnings for the flood forecasting systems. Therefore, the study of the transition from single-cell to multicell was proposed by utilizing vertical vorticity. The mechanisms studied using dual-Doppler analysis (DDA) were further reviewed to quantify their relationships with vertical vorticity. The characteristics of single-cell could be characterized using vertical vorticity, where the formation height of the peak of core pair vorticity occurred at 4.4 km, and their peak of vortices developed at the same time of occurrence using pseudo-vorticity. Meanwhile, dual-Doppler vorticity analysis observed its formation height at 3.8 km and 3.7 km for positive and negative vorticity, respectively, which occurred in the same period. It was assumed that the period of peak intensity occurred at a similar time for single-cell, which was related to the initial formation of the updraft. The results of mechanisms analysis from the evolution of cell development were mainly affected on the increment of core vorticity intensity. The convergence, updraft, and stretching of the vortex tube were influenced on the increment of core vorticity intensity, especially at the lower level, and the tilting of the vortex tube was mostly affected at the middle-level height. At the later stage of multicell formation, the mature vortex was discovered with the core vorticity maxima boundary remaining due to the existence of updraft and convergence in the development of multicell.

Localized severe heavy rainfalls have frequently occurred in Japan. For reducing the damages by disasters, it is necessary to predict the risk of GHR. Kim and Nakakita (2021) developed the quantitative risk prediction method by considering the relationship between the predicted risk level and the variables based on the stages, which are defined by just time. In time stages, the development of GHR was tracked at 5-minute intervals. However, the length of the whole life of GHR depends on the cases, for example, the second 5-minute interval does not necessarily have the same meaning in the development of GHR for different cases. If we consider the development of GHR based on the statistical and physical aspect, we should make more precise predictions. Therefore, this research aims to show the potentiality of the quantitative risk prediction.

Line-shaped convection systems have caused great damage in recent years. While the maintenance mechanism elucidated, the outbreak mechanism is still unexplained. First, using Cloud Resolving Storm Simulater, we conducted a present experiment and found that there were waves when the line-shaped convective system. Then, using Large Eddy Simulation, we conducted a numerical experiment. As a result, self-organization occurred, and we analyzed the outbreak of the rain area. It turns out that air with low potential temperature propagated from Awaji Island to Mt.Rokko. It can be said that this air could push up the air in the south of Mt.Rokko. In the future, we will conduct sensitivity experiment to investigate the effect of Awaji Island and Mt.Rokko.

To alert flash flood warnings on the watersheds of the Toga River basin in Japan, flash flood guidance (FFG) was considered to determine the criteria for whether flash floods occur. FFG is the amount of precipitation needed in a specific period of time to initiate flooding on the watershed. FFG was estimated based on Threshold Runoff (TR) and Soil moisture Deficit (SD) using the Storm Water Management Model (SWMM). In this research, using topographic (i.e., DEM, land use, crosssection, etc.) and meteorological (i.e., radar rainfall intensity) data, FFG was estimated on the mixed land use consisting of the rural and urban areas. So, FFG can issue flash flood warnings without running the entire hydro-meteorological process in the region where flash floods frequently occur. As a result of the calculation of the flash flood guidance, the value at 10 minutes rainfall duration ranges from 9.97 to 23.89 mm when flash floods occur in the Toga River basin.

Offshore wind power station is strongly demanded to complete the zero-emission society. The stations are usually located in shallow water areas where sea waves and currents may cause the scouring in the monopile-support ground. In order to prevent the scouring at the footstep of the monopile, a permeable and flexible filter-unit is developed. The unit is composed with the strong outside net and inner rubbles. The paper describes the experimental study on the stability of the unit in the stormy wave and currents. The test is done in a large basin 45m long and 4m wide and the scale of the model is 1/60. The limitation wave height and current velocity for 8ton unit is revealed.

For a building with a passive control system, an inverse problem is formulated based on the pole allocation method in control theories. The structural system is simplified as a 3DOF damped lumped-mass shear model. The model can express an earthquake resistant structure, a base-isolated structure, an interstory-isolated structure, or a structure with a tuned mass damper or viscous dampers by changing its parameters adequately. The natural frequencies and the corresponding damping ratios in three vibration modes are set as the initial control target for performance-based design. The introduced closed-form expression explains how model parameters are related to the control target, and the mathematical expression generally proves the trade-off relationship in passive control effect. The relationship is extended to an MDOF damped-mass shear model. The numerical examples indicate that the pole allocation has arbitrariness in selecting a solution and a limited solution can be applied to the actual building.

In the Baiu season, heavy rainfall often occurs and has caused a lot of damage in Japan. In this research, since the supply of water vapor is essential for the back-building convective system to occur and be maintained, the water vapor inflow path to the heavy rainfall area along terrain was focused on the meso-α~β-scale. Indeed, such a water vapor inflow path can be confirmed by three-dimensional water vapor flux in this research. Moreover, since atmospheric stability which is changing due to global warming can change the flow, a hypothesis that atmospheric stability can affect the water vapor inflow stability condition was changed with the reproductive experiment. As a result, if the atmospheric condition is more stable, water vapor flux gradually becomes thinner and higher due to the stronger convergence along terrain, and the total inflow of water vapor flux is also increased slightly. In addition, the tendency that such amplifying of the water vapor flux happens under more stable conditions was confirmed in the past real cases by the clustering classification of the past cases.

Ensemble data assimilation experiments for a quasi-geostrophic model are conducted with the deterministic ensemble Kalman filter under an idealized mid-latitude ocean with double gyres. The model uses the Arakawa Jacobian for the nonlinear term and the multigrid method to solve the Helmholtz equation. To reduce pseudo correlation and increase the apparent sample size, the forecast error covariance matrix is localized by Schur product of a Gaussian function of the distance between two grid points. Localization can be applied to the blocks of the forecast error covariance separately by variable decomposition. The innovations of a diagnostic variable (streamfunction) correct the prognostic variable (potential vorticity) through the forecast error covariance between the two, indicating that the analysis of the potential vorticity is essential. By contrast, the analysis of the streamfunction only smoothes vortices in a few cycles and results in an ensemble collapse.

Railway operators enforce train operation control based on actual precipitation observed by rain gauges to ensure safe train operation in heavy rainfall events. Now by utilizing rainfall forecasting information they may make train operation safer. In this study, we study about a prediction method combining the translation model and the orographic rainfall model. About the area around Mt. Hakone when typhoon No. 19 in October 2019, we verified the prediction accuracy and examined the utilization method from comparisons with observation values of rain gauge. As a result, it was found that the estimation accuracy of the rain gauge observation value is improved by considering the orographic rainfall comparing with the case of the translation model only. In addition, we proposed a method to obtain a wide range information of prediction from multiple prediction results obtained by radar data of multiple altitudes.

In recent years, heavy rain disasters caused by line-shaped rainband have become a major problem. Early evacuation is important in order to protect human life, but it is difficult to accurately predict the occurrence of line-shaped rainband, which is necessary for evacuation decisions. In this study, we developed a method for extracting line-shaped rainband from the predicted rainfall of meso-ensemble model output by elliptical approximation. As a result, we were able to achieve 85.1% missing rate (predicted to occur, but not actually occur) and 5.4% occurrence prediction rate. Compared with the existing method, missing rate was 10.5% lower and occurrence prediction rate was 17.5% lower. It is considered that the utilization of this method for evacuation decisions contributes to the reduction of heavy rain disasters.

Crustal deformation is closely associated with hazard risks. We have developed a crustal deformation visualization system for understanding the relationships between contemporary crustal deformation and geographical information such as topography, stratigraphy, and land use. The system is composed of three major functions. The terrain is visualized by a 3D map with arbitrary maps such as aerial photographs and elevation contour maps. A graphical user interface is provided to explore the 3D visualization. If GNSS are classified into several groups of similar velocities, they are indicated by colored symbols on the 3D terrain map, which underline major GNSS velocity discontinuities. Furthermore, every GNSS time-series evolution is displayed by animation. This intuitive data visualization system contributes to both scientific applications and geography classes on earthquake hazard study in primary and secondary education.

Temperature measurements were used to estimate the level of fault friction of large earthquakes. These observations were made in boreholes drilled into fault-zones following large earthquakes in Taiwan, China and Japan. From the temperatures, we are able to estimate the heat generated at the time of the earthquake and thus the level of friction on the fault. The results for all three earthquakes show that the coefficient of friction during the earthquake was 0.1 or less. This is much smaller than values for rock friction measured in the laboratory. The friction determined from rock mechanics experiments represents static friction values, while the temperature measurement values are the dynamic friction during large slip of earthquakes. So static friction of rocks is much higher than the dynamic friction during large earthquake slip.

The objective of this paper is to summarize the research activities of Research Center for Disaster Reduction Systems (the DRS), DPRI. The activities include research seminars inviting guest speakers from various fields such as disaster risk manager of the public sector, researchers, education sector and mass-media. Camping involving academic staffs as well as students is also a highlight of our activities. Research projects funded by the government as well as outside funding bodies are introduced.

The author was born in the northwest edge of Hyogo prefecture. His home was located near sea. The bitter and pleasant experience at seashore brought him up to work for national land management projects through Tottori university, Ministry of Construction, JICE, MLIT, ICHARM and finally DPRI, Kyoto university. The field of the work assigned to seacoast conservation, dam planning, river administration, river planning, local work office management, consulting MLIT, conducting training course, extreme analysis and climate change impact analysis. The tangent hyperbolic function appeared three times. The author introduced the function as if he was charmed by the function. This article is not classified into scientific paper but a kind of autobiography. He says to the young people 1) do by yourself when you lost, 2) have wide experience and wide spectrum of approach and 3) have a deep insight.

The Large-Scale Earthquake Countermeasures Law was put into effect when I started my career as an earthquake scientist. During my early career, I was devoted to administrative jobs related to the Tokai earthquake prediction. However, I had been skeptical of this program, because I have watched several evidence that cast doubt about its expected outcome. Thus, it may be my destiny that I took part in the abolition of the Tokai scheme. On my retirement, it is not a bad idea to present my experience as a government official and professor of Kyoto University; dream and reality of earthquake prediction. Based on my 30-year long experience, I would like to advise that it causes a trouble to establish a system using immature science.

Most of rivers in civilized countries have lost biodiversity due to deterioration of habitats by the artificial river works such as channelization, sand mining and dam construction. The Uji River is a typical river suffered by degradation and bipolazation of the riverbed due to reduced sediment dynamism and step-wise flow regime caused by the gate operation at Seta Barrage for control the discharge from the Lake Biwa, leading to decreased the connectivity of the main channel and the bank side lentic habitats. In this paper, we analyzed relations of aquatic animal communities in lentic habitats to the riverbed geomorphological parameters such as relative height of the habitat to the main channel, the length of cross-sectional perimeter, floodplain vertical shape index (FVSI), and clay layer distribution. Based on the results, the lentic habitats were classified into three types: 1) Low relative height ponds with high biodiversity with taxonomic groups common with lotic habitats, 2) terrace ponds with intermediate and high relative height with low biodiversity with taxonomic groups common with moor-like still water habitats, 3) island bar ponds with high relative height with rather high biodiversity. In addition, we found that the location of these lentic habitats showed a fairly good correspondence to the clay layer distribution. Based on these interrelationships, we proposed a method for evaluation of lentic habitat potential combining a suitable relative height with the underground clay layer distribution. This method will be applicable to nature restoration plans for creation of lentic habitats in degraded rivers in general as well as in the Uji River.

We observed the density of newly fallen snow with K-band vertical radar in Niigata prefecture, Japan. Focusing on the effect of riming on the density of newly fallen snow, we investigated the characteristics that appear in vertical radar observation data when riming growth is dominant: an increase in fall velocity and a decrease in the vertical gradient of radar reflectivity. In the case of graupel dominance, the increase in fall velocity was observed, and in the case of graupel-like snow dominance, the decrease in the vertical gradient of the radar reflectivity was observed.

Relative gravity values were repeatedly measured at 19 gravity points in and around Sakurajima Volcano in October 2021 and March 2022, to monitor spatiotemporal mass variations associated with volcanic activity. The gravity values obtained from 1998 to 2022 showed a clear increase of up to +4.3 Gal/yr in the central part of the volcano. The gravity increase can be explained by the point mass increase of 8 × 109 kg/yr under the center of the volcano at a depth of 3 km below sea level. This result implies that volcanic mass continuously increases under Sakurajima Volcano, even during the quiet period of eruptive activities at the Minami-dake crater.

This paper summarizes the studies on three active faults, which the author has carried out through extensive observations and experiments. First, the Nojima fault is one part of the earthquake source fault of the 1995 Hyogo-ken Nanbu earthquake (M 7.3), and its healing process after the earthquake was studied by repeated water-injection experiments using three boreholes drilled through or close to the fault. We observed fault-zone trapped waves for injection-induced and background ultra-microearthquakes, and estimated deep structure of the Nojima fault. The second is the observation and analysis of typical fault-zone trapped waves in the subsurface survey tunnel excavated through the Mozumi-Sukenobe fault, one part of the Atotsugawa fault zone. The third is the Yamasaki fault zone. We estimated 3-D image of scattering strength around the fault by analyzing coda waves observed by dense temporary and routine seismic stations. We also studied generating properties of micro to small-scale earthquakes in heterogeneous source area., 本稿著者は，これまで行ってきた幾つかの活断層地域での研究について，2022年2月22日開催の令和3年度京都大学防災研究所研究発表講演会にて特別講演「活断層での観測・実験・研究とともに－野島断層・山崎断層・跡津川断層－」と題して講演を行った．本稿はその講演内容をベースとして，多少の補足等も加えて簡潔に取りまとめたものである．

In the present study, we analyzed the particle size distribution (PSD) of falling volcanic ash particles collected for a total of 205 eruptions in 2018-2020 at Sakurajima volcano in Kagoshima Prefecture, Japan. PSD data were measured with the DPRI optical disdrometer network. Assuming the gamma PSD model, we examined the relationships between each of the gamma PSD parameters calculated by the complete moment method. It was shown that there were good correlations between each of the gamma PSD parameters, which might be one of the characteristics of falling volcanic ash particles. We confirmed from the normalized gamma PSD analysis that the normalized intercept parameter and mass-weighted mean diameter are suitable for estimating the ash fall rate. The results of the present study provide essential information for studying microphysical processes in volcanic ash clouds and improving ash transport and sedimentation models. We also derived theoretical power law relationships between pairs of integrated PSD parameters, which can be applied to weather radar monitoring of ash fall distributions.

Experimental assessments for a pillar-coupled electric benchmark platform at anchor are reported, which made on a test platform. Development of a geodetic platform at the center of flooded calderas have been highly demanded to improve the monitoring of the Aira Caldera. If geodetic observation in the center of the caldera is available, accuracy of the monitoring can be improved significantly. GNSS on the universal-coupled pillar at anchor is applied as a fundamental architecture of the platform. The design of the actual platform includes following four problems to be examined ; 1) year-long stability of Kinematic method, 2) optimum tilt detection method, 3) velocity responses, and 4) construction of tilt correction algorithm. Test of these all problems were successful and GNSS antenna array system is decided to apply the actual platform.

A constitutive model for a nonlinear elastic body within a framework of multiple shear mechanisms has been proposed to consider the geometrical nonlinearity based on large deformation (or finite strain) theory. The constitutive model has been extended to incorporate the effect of inherent anisotropy based on the total Lagrange method in the large deformation theory. This manuscript presents a formulation based on the updated Lagrange method to complete the description of a nonlinear elastic body model that can consider the inherent anisotropy effect as well as the geometrical nonlinearity.

Both sounding and sediment sampling on the sea bottom have been carried out by the same method as the last time in Yotsuyahama coast on July.27 2011, July.24 2012, Sept.30 2014, and Oct.2 2014. Several sedimentary samples on the sea bottom have been tried to analyze into the grain size with precise accuracy. Also, these datas were attempted to analyze surely. Double crescent-shaped bars were found out on those two measuring lines of the sea bottom. It was shown clearly that the existence of submerged breakwater has given the full influence to the sedimentation of the sea bottom. The results of data analyses on both the bottom profile and the grain size composition of the sediment on the sea bottom provide some ideas to understand the reasons for the coastal erosion.

The impact of climate change on sediment hazard occurrence is urgently needed to resolve for pursuing the future sustainable living environment. To this end, this research aims to propose a new approach to physically quantify the change of snake line patterns with the application of Clausius-Clapeyron scaling law. The key of the proposed approach is to establish the physically based linkage among air temperature change on ground surface, peak precipitation intensity, and corresponding snake line pattern of certain percentiles of rainfall events. In this study, we used 99th and 50th percentiles for representing extreme and general precipitation conditions. With the long-term meteorological observation at Kobe meteorological observatory, we successfully verified the applicability of the proposed approach on identifying the change of snake line pattern. The regional climate projections of 5-km NHRCM were then analyzed to examine the future change of Clausius-Clapeyron scaling in the Japanese archipelago. Meanwhile, we also revealed the future change of snake line patterns under climate change influences.

Wind speed in the atmospheric boundary layer (ABL) changes in a variety of time scales. During autumn season, stability of the ABL varies from near neutral to unstable conditions in the daytime. This certainly affects the wind near the surface. In this study, variation of the wind at two places was investigated. At the Ujigawa Open Laboratory in Kyoto City, intermittent events of large fluxes in the surface layer were observed by sonic anemometers at around midday and in the afternoon. On the other hand, at the Nagoya Local Meteorological Observatory in Nagoya City, a wind profiler shows that the difference of wind speeds at the observation levels becomes small in the morning and the wind speeds gradually increase in the afternoon.

Microtremor measurements were conducted in the Ujitawara and Wazuka basins, southern part of Kyoto Prefecture. The H/V spectra were obtained at 42 sites in Ujitawara and 37 sites in Wazuka. The peak frequency of H/V spectra was 0.9-1.4 Hz at sites in the western part of the Ujitawara Basin, whereas it was high (7-10 Hz) in the Iwayama area, the eastern part of the basin. The H/V peak frequency was high (2.5-16 Hz) in the valley bottom lowland along the Wazuka River. It was 1.0-2.3 Hz in hills of the Osaka Group, and it indicates that the thickness of sediments deepens towards the Wazukadani Fault. The estimated bedrock depth by the microtremor array survey was 165 m in the western part of the Ujitawara Basin. Small-sized microtremor array surveys were also conducted in the Ujitawara and Wazuka basins. The estimated phase velocities were relatively high, suggesting that the alluvium low-velocity sediments are thin in these two basins.

To reveal the geological and geomorphological causes of deep-seated catastrophic landslides (DCLs) by heavy rainfall in the 1953 Aridagawa disaster, detailed geological mapping and geomorphological analysis using 1-m DEMs were undertaken in the upper reaches of the Arida River in the Kii Mountains. This area is underlain by the Cretaceous accretionary complex, consisting of sandstone dominated alternating beds of sandstone and shale and their broken formation. As a result, southward dipping low-angle faults, shear planes of broken formation with laumontite veins and the Yanase fault formed the failure surfaces and most of the DCLs were distributed along the convex slope breaks, undercut slopes and ridge lines with deep weathered rocks.

Eruption hazard caused by volcanic bombs and volcanic ash at Suwanosejima volcano is examined using infrasound. The explosive eruption, which ejected volcanic bombs to distances around 1 km, occurred during high explosivity with infrasound larger than 200 Pa. The high explosivity accompanied only a low plume (

Field observations and numerical simulations were conducted to clarify the flow characteristics of mudflows in the Aizome River basin, Atami City, where multiple mudflows occurred on July 3, 2021. Additionally, evacuation methods from mudflows in a residential area with a high-risk valley of sediment disaster was discussed. The results show that the Aizome River basin has a well-defined valley topography, and the mudflows were not spread out much across the valley, but flowed within a width of 80 m or less. This indicates that evacuation is possible only by moving several tens of meters in the direction perpendicular to the flow direction.

Multifractal has been widely applied as the tool of quantitative pattern analysis. We investigated multifractal properties of water vapor flux and precipitation particles distribution associated with line-shaped rain bands to identify the three-dimensional patterns of selforganization of convection systems. We analyzed water vapor flux obtained by the numerical simulation of the heavy rainfall event over Kameoka City on 15 July 2012. Before heavy rainfall occurred, water vapor flux approached to monofractal corresponding to increasing the convective instability at lower atmosphere. While during heavy rainfall, strong multifractality was shown due to the development of convection systems. Multifractal analysis was also conducted to characterize the multifractality of the mixing ratio distributions of ice-phase precipitation particles obtained by volume scans of X-band MP radars. The time period when the line-shaped rain band area began to expand and the regional averaged rainrate increased coincided with the one when the multifractality of the graupel and snowflake mixing ratio changed significantly.

I have briefly described the relationship between slopes of Japan and the lives of the Japanese people from the past to present. The mountain slopes of Japan are covered with a huge amount of Holocene slope deposits. The old mountain villages are located on landslides, and the Japanese are a people who have lived with landslides. We can also find slope deposits by historical earthquakes, and some old folk customs on landslide villages. Due to the post-war changes in socio-economic system, urban landslide disaster became prominent and serious. Repeated earthquake disasters have revealed the remarkable risk of embankment of residential area in urban region. The “foretold disaster studies” involved the socio-economical perspective are proposed as a new discipline that comprehensively investigates the risks involves in the “semi-hazardous place”, which is a grey zone of safety. The purpose of this new discipline is to try to restore the “wildness” of the Japanese with geological literacy., 本稿は，2022年2月22日と3月5日に行った退職記念講演の内容に加筆したものである.

A sparse interpolation matrix is constructed as the differentiation matrix using Gaussian radial basis functions (RBF). Error convergence and eigenvalue stability analysis are investigated in a test case for shallow water models (SWM) with a local nonlinear zonal geostrophic flow. The convergence study shows that the SWM made with the sparse interpolation matrix is more accurate than made with the RBF-FD (finite-difference) method. The former model is more stable than the latter because the eigenvalues of the former model lie more closely along by the imaginary axis than those of the latter.

The investigation of merging cells from new cells to multicell in thunderstorms using vertical vorticity analysis will be proposed. The vertical vorticity analysis using pseudovorticity that used only one single radar and Dual Doppler analysis (DDA) vorticity were applied to the rainfall event on 10th September 2014 with the condition of an unstable atmospheric environment with the weak vertical shear. The core pair vorticity was identified by selecting the maximum quantitative vorticity intensity at each boundary of the new cell and multicell. The comparison of time series core pair vorticity was established before, during, and after the merging cells. It was found that at the early stage of merging cells, new cell B indicated the largest intensity with cell A (older cell), whereas other new cells showed lower strength compared with the multicell after the later stage of multicell formation. This signature pattern was identical for the pseudo-vorticity and DDA vorticity analysis. By employing vertical velocity analysis, the core of the updraft was located between the pair of vorticities which influenced the construction of vertical vortex tubes with the existence of weak wind shear. The supportive mechanism that resulting in the intensification of core pair vorticity was established by examining the convergence, stretching, and tilting of the vortex tube. The convergence plays the main role in the intensification of core vorticity which influenced the stretched of vortex tube to rotate rapidly that generated the increment of core vorticity, meanwhile tilting was less affected to this increment pattern. In conclusion, the signature pattern of merging cells could be observed on the strength of core pair vorticity during the merging cells.

This study investigates the dynamical variability of the double-jet structure in the Northern Hemisphere summer months of June and July. The summer northern annular mode (NAM), which is the leading mode of the empirical orthogonal function analysis in the extratropical troposphere for each month, is used for this analysis. The strong positive NAM is characterized as the double jets with the subtropical jet located at around 40°N and the polar front jet (the eddy drive jet) at 60°–70°N; the strong negative NAM is characterized as the single jet with the dominant subtropical jet at around 40°N. The vertical profile of momentum budget at 60°–85°N in the strong NAM months has peaks of the EP flux convergence and the poleward absolute vorticity advection at 300 hPa. The difference of zonal wind between the strong positive and negative NAM is estimated at around 5 m s⁻¹.

For 40 years, I have been engaged in a research and education in Disaster Prevention Research Institute (DPRI) and Department of Civil and Earth Resources Engineering, Kyoto University. In the term, I moved to several research sections in DPRI. I would like to introduce what kind of research topics I engaged in and how the research topics were determined in these research sections. I will be happy if the paper can be of any help to your research life.

With the growing importance of taking stepwise adaptation measures to climate change, we conducted a future change analysis of rainfall during the baiu rainy season using 150-year continuous run. We analyzed two aspects about the baiu rainfall: baiu frontal zones based on average daily rainfall in July and baiu extreme rainfall based on hourly rainfall. The results show that the rainfall area gradually moves northward in both the frontal zone and location of the extreme rainfall events. The analysis of future changes in average daily rainfall by region showed that there was a marked tendency for rainfall to in-crease in northern Japan, but there were also regions that contained periods when rainfall was lower than the historical average. The reasons for this are discussed in terms of the influence of sea surface temperatures and typhoons. Furthermore, we showed that the duration of extreme rainfall events will gradually increase in the future.

In this research, potential temperature gradient based vorticity which is the expression of baroclinic is obtained to analyze the energy structure of the vorticity field in developing clouds. First, applying the variational method enables us to obtain a diagnostic equation in which the equation of motion, conservation law of mass, and entropy are considered as constraints. Second, Fourier analysis was performed on the vorticity field in the cross-section of the convective core in the isolated cumulonimbus simulation. The temporal change of the spectrum of vorticity field indicates that the rotational intensity of potential temperature gradient based vorticity increases as the degree of baroclinicity increases. Third, we conducted the data assimilation experiment assuming the use of vertical vorticity estimated by doppler radar observation. The change in the potential temperature and vertical wind through the error covariance matrix generates coherent convection in the computations.

Born in Shikoku, I was deeply affected by the large-scale landslide disaster that occurred in Kochi Prefecture in 1972. The landslide killed a number of rescue workers who were searching for missing persons after the first small slope failure. I believe that this catastrophe motivated me to become a researcher in the field of sediment-related disasters. Now, 37 years have passed since I became a member of the Forestry and Forest Products Research Institute, and I have retired from the Disaster Prevention Research Institute of Kyoto University. I would like to take this opportunity to share some lessons learned from my extensive research experience. 1) Failure in trial and error is inevitable; so, let us overcome it with ingenuity. 2) Steady efforts are always rewarding; you may be able to pick up gemstones on the roadside. 3) Do not be afraid to take on bold challenges after understanding the associated risks; when faced with serious problems in the field, you gain immeasurable knowledge. 4) Consider following an interdisciplinary approach in your research; avoid stereotypes as more often than not, such approach results in breakthrough ideas. I hope my experience will be helpful to young scholars in alleviating their uncertainties and problems.