Abstract
In recent years, social interest in climate change such as global warming has been increasing due to the report of an increase in extreme events. However, prediction such as heavy rain, which is one of extreme phenomena, is difficult to predict since the phenomenon itself occurs on a very local spatial scale. On the other hand, the water isotopic ratio is a physical quantity sensitive to phase change of water, which is advantageous for exploring details of the local precipitation process. In this study, we analyzed the isotope ratio fluctuation during heavy rainfall observed in Mase, Tsukuba city, Ibaraki prefecture during the Kanto and Tohoku heavy rains in September 2015. As a result, it became clear that water vapor from different sea areas reached in a short period of time, and the behavior that the water vapor isotopic ratio (δ18O) by IsoGSM increases and decreases from September 8 to 10 is due to the difference in the origin of water vapor. The Amount Effect usually refers to the apparent statistical relationship between the precipitation isotopic ratio and the precipitation amount, but the short-term fluctuation of the water vapor isotope ratio is sensitive to the amount of precipitation which was made along the transport pathway of the mass before reaching to the observation site.
