Comprehensive future projections for the line-shaped convective system associated with Baiu front in Japan under RCP scenarios using regional climate model and pseudo global warming experiments

Herein, climate change projections of localized extreme rainfall associated with the Baiu front (Baiu extreme rainfall) are investigated from June to August in Japan under two representative concentration pathway scenarios (RCP2.6 and RCP8.5) by analyzing the numerical simulations of a 5-km-mesh high-resolution regional climate model (NHRCM05), which gives us the probabilistic future projections by using ensemble simulations, and by conducting Pseudo Global Warming (PGW) experiments for two typical events (Kameoka heavy rainfall in 2012 and Hiroshima heavy rainfall in 2014) with the cloud-resolving model, which enables us to elucidate the mechanisms of future change. The NHRCM05 analysis revealed that the frequency of Baiu extreme rainfall would increase by 1.2-times under RCP2.6 and by ≥ 1.5-times under RCP8.5 compared with the present climate. Moreover, the maximum total rainfall would increase due to global warming. To elucidate the mechanisms of rainfall intensification, the PGW experimental results were analyzed. 2012-Kameoka PGW analysis revealed that the rainfall increasing rate was almost twofold compared to the theoretical Clausius-Clapeyron scaling, which was attributed to a nonlinear effect of intensification of the back-building dynamical structure by the convergence in the lower level and the strengthening of the updraft, resulting in localization of water vapor into the cumulonimbus that cause much more buoyancy. Meanwhile, 2014-Hiroshima event experiments indicated that the rainfall decreased with global warming due to water vapor consumption in upstream areas. However, the PGW of 2014-Hiroshima possibly happened to show a decreasing trend as further NHRCM05 analysis of events similar to 2014-Hiroshima showed an increasing trend in rainfall. This study highlights the importance of predicting future changes by combining results obtained from various methods, including climate model analysis or PGW, with a profound understanding of the implications and feature of each result as well as the fact that disaster prevention and adaptation measures are urgently needed

Fundamental Research on Water Vapor Inflow Path into the Back-building Convective System and its Relationship with Atmospheric Stability

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

Future change of occurrence frequency of Baiu heavy rainfall and its linked atmospheric patterns by multiscale analysis

The future change of heavy rainfall (meso-β scale) in the Baiu season, the atmospheric patterns (over meso-α scale) of sea level pressure and surface vapor flux, and the connection between them were investigated by analyzing multiple datasets of a high-resolution non-hydrostatic regional climate model (NHRCM05) for better simulating heavy rainfall, a coarser-resolution global atmospheric climate model (AGCM20) embedding the NHRCM05, and a huge database for Policy Decision-Making for Future climate change (d4PDF) with a coarser-resolution. As a result, northern Japan and Japan-sea-side areas have a statistically significant increase of heavy rainfall that is caused by an increase in the atmospheric patterns with westward-protruding Pacific high and northward-invading vapor flux along the periphery of the high. In the Pacific side in eastern Japan, the typical atmospheric pattern prone to heavy rainfall will change in the future as it will decrease the occurrence frequency of the atmospheric pattern that presently caused heavy rainfall with cyclones located at south of Japan. Besides, the atmospheric pattern with westward-protruding pacific high, that presently caused heavy rainfall mainly in western Japan, will expand the area of heavy rainfall eastward in the future due to an eastward-invading vapor flux

Carbohydrate recognition mechanism of HA70 from Clostridium botulinum deduced from X-ray structures in complexes with sialylated oligosaccharides

AbstractClostridium botulinum produces the botulinum neurotoxin, forming a large complex as progenitor toxins in association with non-toxic non-hemagglutinin and/or several different hemagglutinin (HA) subcomponents, HA33, HA17 and HA70, which bind to carbohydrate of glycoproteins from epithelial cells in the infection process. To elucidate the carbohydrate recognition mechanism of HA70, X-ray structures of HA70 from type C toxin (HA70/C) in complexes with sialylated oligosaccharides were determined, and a binding assay by the glycoconjugate microarray was performed. These results suggested that HA70/C can recognize both α2–3- and α2–6-sialylated oligosaccharides, and that it has a higher affinity for α2–3-sialylated oligosaccharides

Recent nationwide climate change impact assessments of natural hazards in Japan and East Asia

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 important to numerically simulate TC activity (and other phenomenon) on local scales in order to properly assess climate change impacts on natural hazards in the region. In addition, projecting future changes of many TC-related hazards and/or their potential economic impacts can be challenging due to their low occurrence frequencies in any one particular area. With these views in mind, a collaborative research program was formed in Japan to project long-term changes in natural hazards in Japan and East Asia based on local-scale and large-ensemble numerical experiments. This paper reviews recent climate change impact assessments (written in both English and Japanese) from the program and summarizes the projected future changes in precipitation, river flooding, and coastal hazards, and their associated economic impacts

メカニズム解明に向けた線状対流系過去事例群の統合的物理解析

The purpose of our research is to investigate the environmental conditions for the occurrence and development of line-shaped convective systems associated with stagnant Baiu front by comprehensively analyzing past events and considering spatio-temporal scale. As a result, type-A, which is large scale, long duration, and occurs near convergence of Baiu front, occurs due to large convergence of the front, so the environmental condition of type-A is not necessarily idealized. In contrast, type-B, which is small scale, short duration, and occurs far from Baiu front, occurs at more limited and idealized environment than type-A. This strict condition contributes to occurrence and self-organized development of the first convective cloud. We also show that requirements for the first cloud are convective instable, large CAPE and vertically big change of direction of wind. Moreover, our results bring that the constant ratio of buoyancy to turbulence is important for occurrence and development