2022 年 10 巻 1 号 p. 30-44
The 2019 Typhoon Hagibis brought heavy rainfall to eastern Japan. In the downstream basin of the Arakawa River, which is located in the Metropolitan area, the water level rose close to the inundation risk level. As flooding is likely to occur in the downstream basin in the event of still heavier rainfall, it is necessary to obtain data on increased rainfall as basic information for the planning of evacuation activities. This paper reports the results of a reproducibility study together with an analysis of changes in rainfall due to manipulation of sea water temperature using a Weather and Research Forecasting (WRF) model and of their impact. The overall shape of hyetograph was reproduced in the study, albeit with differences in peak time and amount of rainfall. In addition, it was verified that the amount of rainfall fluctuates in correspondence with fluctuations in sea surface temperature. The study revealed that this is caused by the effect of the topography of the Arakawa upstream basin, in addition to changes in the course of the typhoon resulting from changes in the atmospheric pressure field and fluctuation of the water vapor flux.
