Statistical analyses on the morphology and environmental properties of warm-season quasi-stationary convective clusters in Japan

International Conference on Mesoscale Convective System and High-Impact Weather (ICMCS-XI), BEXCO, Busan, Korea, 25-28 April 201

ORGANIZATION AND INTERNAL STRUCTURE OF PRECIPITATION INDUCED BY TYPHOONS OVER JAPAN

18th Annual Meeting of the Asia Oceania Geosciences Society (AOGS 2021), Singapore, 1 – 6 August 2021This study explores the temporal precipitation organization of 126 landfalling typhoons around Japan during 2006–2019. The internal structure particularly the cell sizes and spell durations of precipitation induced by these 126 typhoons are investigated from the Radar Automated Meteorological Data Acquisition System (Radar-AMeDAS) observed hourly precipitation dataset. The best track data from the Regional Specialized Meteorological Center (RSMC) Tokyo are utilized to identify the typhoon locations. We first stratified the independent precipitation cell sizes and precipitation spell durations with intensity exceeding various thresholds into different bins. Then the frequency distribution of the precipitation sizes and durations in each bin are computed. Our results indicate that the occurrence of typhoon induced heavier precipitation is higher compared to the typhoon induced lighter precipitation. The typhoon induced heavier precipitation over Japan last up to a day, while the lighter precipitation last about 12 hours. The long-lived precipitation cases are also noticed that last up to 2 days, but they don’t occur so frequently. We analyzed the spell durations over different regions of Japan with various radii from the typhoon center starting from 10 km to 300 km. The results also indicate that the pattern of spell durations are mostly same over all the regions within 300 km radius

Assessment of natural hazards due to a category-5 extreme typhoon under global warming by dynamical downscaling experiments

The 7th International Conference on Water Resources and Environment Research (ICWRER2016), Kyoto TERUSA, Kyoto, Japan, 5-9 June 201

Large-Eddy-simulation analysis of airflows and strong wind hazards in urban areas

Understanding the characteristics of urban airflows with complex geometrical features is very important from viewpoints of assessing strong wind hazards in the region. This study investigated turbulent airflows and strong wind hazards in an urban area by conducting large-eddy simulations (LESs) with explicit representations of buildings and structures. A business district, including historical architectures, of Kyoto City was chosen. The sensitivity experiments with realistic and idealized building arrangements indicated that the actual, complicated arrangement of buildings as well as the building height variability would enhance an unsteady nature of airflows in urban canopy. An analysis of strong wind hazards under a typhoon condition shows that sustained winds are stronger along streamwise-oriented major streets and over open spaces while instantaneous winds become stronger especially within areas with a mixture of high-rise buildings embedded in low-rise building areas/open spaces. It was indicated that wind gustiness increases with the decrease in building plane-area index. The analysis suggested that both the building height variability and the complex arrangement of buildings are considered to enhance the gustiness of surface winds. This study demonstrated that an LES model is practically useful for assessing the strong wind hazards in urban areas

Orographic effects on the transport and deposition of volcanic ash: A case study of Mt. Sakurajima, Japan

Volcanic ash is a major atmospheric hazard that has a significant impact on local populations and international aviation. The topography surrounding a volcano affects the transport and deposition of volcanic ash, but these effects have not been studied in depth. Here we investigate orographic impacts on ash transport and deposition in the context of the Sakurajima volcano in Japan, using the chemistry-resolving version of the Weather Research and Forecasting model. Sakurajima is an ideal location for such a study because of the surrounding mountainous topography, frequent eruptions, and comprehensive observing network. At Sakurajima, numerical experiments reveal that across the 2–8ϕ grain size range, the deposition of “medium-sized” ash (3–5ϕ) is most readily affected by orographic flows. The direct effects of resolving fine-scale orographic phenomena are counteracting: mountain-induced atmospheric gravity waves can keep ash afloat, while enhanced downslope winds in the lee of mountains (up to 50% stronger) can force the ash downward. Gravity waves and downslope winds were seen to have an effect along the dispersal path, in the vicinity of both the volcano and other mountains. Depending on the atmospheric conditions, resolving these orographic effects means that ash can be transported higher than the initial injection height (especially for ash finer than 2ϕ), shortly after the eruption (within 20 min) and close to the vent (within the first 10 km), effectively modifying the input plume height used in an ash dispersal model—an effect that should be taken into account when initializing simulations

An analytical representation of raindrop size distribution in a mixed convective and stratiform precipitating system as revealed by field observations

This study investigated a rainfall event under a typhoon influence using a 2D video disdrometer and weather radar observations to characterize raindrop size distribution (DSD) in a mixed convective and stratiform precipitating system. During the time period when both convective and stratiform rainfalls existed, the DSDs generally indicated a monotonically decreasing shape with increasing particle size, with a relatively gradual decrease at intermediate particle size observed at certain times; this feature is attributed to the combined effect of convective and stratiform rainfalls. During the transitional period between convective and stratiform rainfalls, the DSDs exhibited a bimodal shape. The DSDs were well approximated by a newly proposed gamma raindrop distribution combined with exponential (GRACE) distribution function, which was defined as the sum of the exponential distribution and the gamma distribution. A comparison of the volume ratio of the exponential and gamma components of the GRACE distribution revealed that the exponential component of the DSD was larger than the gamma component in the bimodal DSD. These results suggest that the DSD became bimodal during the period when stratiform rainfall predominated because of the weakening of convective rainfall. The GRACE distribution is useful for understanding cloud-microphysical processes in mixed stratiform and convective precipitation conditions

Influence of amplitude regarding finger force on loudness discrimination acuity of self-generated sound

International audienc

Long-term ash dispersal dataset of the Sakurajima Taisho eruption for ashfall disaster countermeasure

Abstract. A large volcanic eruption can generate large amounts ofash which affect the socio-economic activities of surrounding areas, affecting airline transportation, socio-economics activities, and humanhealth. Accumulated ashfall has devastating impacts on areas surrounding thevolcano and in other regions, and eruption scale and weather conditions mayescalate ashfall hazards to wider areas. It is crucial to discover placeswith a high probability of exposure to ashfall deposition. Here, as areference for ashfall disaster countermeasures, we present a datasetcontaining the estimated distributions of the ashfall deposit and airborneash concentration, obtained from a simulation of ash dispersal following alarge-scale explosive volcanic eruption. We selected the Taisho (1914)eruption of the Sakurajima volcano, as our case study. This was thestrongest eruption in Japan in the last century, and our study provides abaseline for a worst-case scenario. We employed one eruption scenario (OES)approach by replicating the actual event under various extended weatherconditions to show how it would affect contemporary Japan. We generated anash dispersal dataset by simulating the ash transport of the Taisho eruptionscenario using a volcanic ash dispersal model and meteorological reanalysisdata for 64 years (1958–2021). We explain the dataset production andprovide the dataset in multiple formats for broader audiences. We examinethe validity of the dataset, its limitations, and its uncertainties.Countermeasure strategies can be derived from this dataset to reduceashfall risk. The dataset is available at the DesignSafe-CI Data Depot:https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-2848v2or through the following DOI: https://doi.org/10.17603/ds2-vw5f-t920by selecting Version 2 (Rahadianto and Tatano, 2020)

SST Ensemble Experiment-Based Impact Assessment of Climate Change on Storm Surge Caused by Pseudo-Global Warming: Case Study of Typhoon Vera in 1959

金沢大学理工研究域環境デザイン学系To evaluate future changes in storm surge caused by global warming, dynamical downscaling was conducted using the Weather Research and Forecasting model for Typhoon Vera under present- and future-climate conditions and storm surge simulation using the Coupled Model of Surge, Wave, and Tide. The present-climate experiment entailed dynamical downscaling using data from the Japanese 55-year Reanalysis project as the initial and boundary conditions, and the future-climate experiments entailed downscaling considering future changes simulated through sea-surface temperature ensemble experiments using the Meteorological Research Institute Atmosphere General Circulation Model. The characteristics of the downscaled typhoon agreed well with the Best Track, and the future changes in the typhoon characteristics were as follows: intensification of the central pressure, delayed decline in the high-latitude area, and westward track migration. Present-climate storm surge simulation executed using these downscaling results after correcting for the track error agreed with the observed surge, but the storm surges under future-climate conditions were underestimated because of differences in the typhoon track and surface roughness. Storm surge simulations were conducted using an empirical typhoon model; the results suggest a storm surge of 26cm (average of the ensemble) at Nagoya Port, which is located in the innermost region of Ise Bay. © 2017 World Scientific Publishing Company.Embargo Period 12 month