[H-CG23] Adaptation to climate change and its social implementation

[HCG23-P06] Climate change impact estimates of flood risk from atmospheric rivers

*Shamoto Akihiro¹, KOJI DAIRAKU² (1.University of Tsukuba, 2.University of Tukuba)

Keywords:Flood Risk, Atmospheric rivers , Climate Change

Atmospheric rivers are large, elongated water vapor flows that transport moisture from the tropics to mid- and high latitudes. The effects of atmospheric rivers are very important in North America, Europe, and East Asia because they cause flood damage in large amounts and drought-suppressing rainfall in smaller amounts. In recent years, East Asia has experienced a series of heavy rainfall events caused by large-scale water vapor inflow, such as the August 2021 rainstorms. Previous studies have shown that atmospheric rivers may be associated with 40% to 70% of the strong precipitation during the rainy season. On the other hand, atmospheric rivers that land in Japan have various shapes (paths and directions), and the areas where heavy rainfall occurs differ depending on the shape. Therefore, it is an important research issue to investigate the characteristics of atmospheric rivers that cause heavy rainfall. Therefore, my objective is to identify the characteristics of atmospheric rivers that cause heavy rainfall damage based on the data of atmospheric rivers that have landed on the Japanese archipelago in the past and flood damage statistics. The data of atmospheric rivers that have landed in Japan in the past are based on the JRA-55 with a horizontal resolution of 1.25° × 1.25° and a temporal resolution of 6 hours. Atmospheric rivers are extracted based on specific humidity and horizontal wind speed obtained from the reanalysis data. Flood damage statistics data compiled by the Bureau of Water Management and Land Conservation, Ministry of Land, Infrastructure, Transport and Tourism are used. Specific parameters are scale, path, direction, atmospheric conditions, and persistence. By clarifying the relationship between the characteristics of strong precipitation caused by atmospheric rivers landing in Japan and the associated flood risk. It is possible to estimate the impact of future changes in atmospheric circulation and temperature due to climate change on flood risk. This research will contribute to the early prediction of flood damage levels caused by heavy rainfall and to the estimation of the impact of climate change, which will lead to disaster prevention and mitigation in Japan.