The impacts of flooding are expected to rise due to population increases, economic growth and climate change. Hence, understanding the physical and spatiotemporal characteristics of risk drivers (hazard, exposure and vulnerability) is required to develop effective flood mitigation measures. Here, the long-term trend in flood vulnerability was analysed globally, calculated from the ratio of the reported flood loss or damage to the modelled flood exposure using a global river and inundation model. A previous study showed decreasing global flood vulnerability over a shorter period using different disaster data. The long-term analysis demonstrated for the first time that flood vulnerability to economic losses in upper-middle, lower-middle and low-income countries shows an inverted U-shape, as a result of the balance between economic growth and various historical socioeconomic efforts to reduce damage, leading to non-significant upward or downward trends. We also show that the flood-exposed population is affected by historical changes in population distribution, with changes in flood vulnerability of up to 48.9%. Both increasing and decreasing trends in flood vulnerability were observed in different countries, implying that population growth scenarios considering spatial distribution changes could affect flood risk projections.

Estimates of future flood risk rely on projections from climate models. The relatively few climate models used to analyze future flood risk cannot easily quantify of their associated uncertainties. In this study, we demonstrated that the projected fluvial flood changes estimated by a new generation of climate models, the collectively known as Coupled Model Intercomparison Project Phase 6 (CMIP6), are similar to those estimated by CMIP5. The spatial patterns of the multi-model median signs of change (+ or −) were also very consistent, implying greater confidence in the projections. The model spread changed little over the course of model development, suggesting irreducibility of the model spread due to internal climate variability, and the consistent projections of models from the same institute suggest the potential to reduce uncertainties caused by model differences. Potential global exposure to flooding is projected to be proportional to the degree of warming, and a greater threat is anticipated as populations increase, demonstrating the need for immediate decisions.

No abstract

The conjugation of horseradish peroxidase with wheat germ agglutinin was used to identify the effect on retrograde axonal transport of stretching the rat sciatic nerve indirectly by 10% and 20% femoral lengthening with a unilateral external fixator. To investigate the relationship between retrograde axonal transport and blood flow in the stretched nerve, nerve blood flow in the sciatic nerve was measured by a hydrogen washout technique. At 11% strain (20% femoral lengthening), the numbers of horseradish peroxidase-labelled motor neuron cells and nerve blood flow had decreased by 43% and 50%, respectively. Histological examination demonstrated ischaemic changes, but not mechanical damage. However, at 6% strain (10% femoral lengthening) there were no significant abnormalities. These findings suggest that the inhibition of retrograde axonal transport can be induced by acute stretching of the peripheral nerve and that circulatory disturbance is the main cause of the inhibition of retrograde axonal transport at the low strain.

No abstract

Water isotopic composition (δ 18 O and δD) in terrestrial proxies of past precipitation enable us to better understand and interpret variation in the Indian Summer Monsoon (ISM). Previous studies have suggested that the origin of precipitation is an important factor controlling the isotopic composition of precipitation around the Indian subcontinent; however, it is difficult to quantify using the Lagrangian approach because the approach does not satisfy the assumption of an adiabatic process over a convective area. We investigated the isotopic composition of precipitation at three sites over Bangladesh in 2010 and estimated the origins of precipitation by the Eulerian approach using an isotope-incorporating Atmospheric General Circulation Model. Our observations showed similar seasonal and intraseasonal variations in the δ 18 O values of precipitation among the sites, whereas the temporal characteristics of the precipitation amount differed among the sites. The isotopic composition was linked to the migration of organized convective activity around the region. The model showed that the pre-monsoon season (from mid-March to early June) was characterized by high δ 18 O values of precipitation originating from the Bay of Bengal and the Arabian Sea. In the ISM season (from mid-June to early October), the contribution of these sources to precipitation gradually decreased, while the contribution from the Indian Ocean increased, resulting in decreasing δ 18 O values of precipitation due to the enhanced rainout process during the transportation. These moisture contributed less to precipitation over Bangladesh in the post-monsoon season (from mid-October to November), whereas moisture originating from the Pacific Ocean and land surface (i.e., recycling of water) contributed to precipitation in the season. Because the recycling of water originated from past precipitation with low δ 18 O values in the ISM season, its contribution to precipitation reduced the δ 18 O values of precipitation in the ISM and post-monsoon seasons. These results suggest that the origins of precipitation and the migration of organized convective activity are the dominant factors controlling the isotopic composition of precipitation in the region. These characteristics can be used to identify monsoon onset and withdrawal based on water isotopic composition.

The modulation of large-scale moisture transport from the tropics into East Asia in response to typhoon-induced heating during the mature stage of the Baiu/Meiyu season is investigated using the Japanese 55-year reanalysis (JRA-55), aided by a Rayleigh-type global isotope circulation model (ICM). We highlighted the typhoons that migrate northward along the western periphery of the North Pacific subtropical high and approach the vicinity of Japan. Anomalous anticyclonic circulations to the northeast and southeast of typhoons and cyclonic circulation to their west become evident as they migrate toward Japan, which could be interpreted as a Rossby wave response to typhoon heating. These resultant anomalous circulation patterns form moisture conveyor belt (MCB) stretching from the South Asian monsoon region to East Asia via the confluence region between the monsoon westerlies and central Pacific easterlies. The ICM results confirm that the well-defined nature of the MCB leads to penetration of the Indian Ocean, South China Sea, Philippine Sea, and Pacific Ocean water vapors into western Japan. The typhoons have the potential to accumulate large amounts of moisture from distant tropical oceans through the interaction of their Rossby wave response with the background flow. In the case of a typical typhoon, the total precipitable water around the typhoon center as it approaches Japan is maintained by the moisture supply from distant oceans rather than from the underlying ocean, which indirectly leads to the occurrence of heavy rainfall over western Japan.

The seasonal water cycle features over the maritime continent were determined using water sources from seven regions produced by global Rayleigh-type circulation model. The model output was validated statistically to reproduce stable isotopes by the observed δ 18 O and δ D content of precipitation at eight stations. The model explains the Asian-Australian monsoon circulation well and demonstrates the seasonal changes of the water origin on the basis of three climatic patterns as a signature of rainy and dry season:(1) the semi-annual pattern, seasonal changes are indicated by the raise of water vapor from Indian Ocean for rainy season and southern maritime continent for dry season (2) the anti-monsoonal pattern, represented by the alternating raise and retreat of water vapor from the southwest Pacific Ocean, southern and tropical maritime continent seas, and (3) the monsoonal pattern, characterized by the raise water vapor from the Indian Ocean and northern maritime continent sea for rainy season and southern maritime continent seas for dry season.(Citation: Suwarman, R., K. Ichiyanagi, M. Tanoue, K. Yoshimura, S. Mori, M. D. Yamanaka, N. Kurita, and F. Syamsudin, 2013: The variability of stable isotopes and water origin of precipitation over the maritime continent. SOLA, 9, 74−78,