On the Mayu front near China and the Baiu front near Japan, a large amount of precipitation is brought about by the confluence of the westerly wind and the east wind and a large amount of water vapor is transported, often causing meteorological disasters.The heavy rain in July 2nd year of Reiwa, which caused enormous damage to the Kyushu region, is one of them.

　In this study, in order to understand the frequent occurrence of recent heavy rain disasters, we investigated the long-term changes in the rainfall in the Baiu front zone using the data of the rainfall radar mounted on the artificial satellite.By utilizing the unique data of direct observation of precipitation from space, it has become possible to analyze with homogeneous measured data over a long period of time.

　As a result of the analysis, it was confirmed that the precipitation activity in the Baiu front zone in the 2010s was clearly more active than in the 2000s before that.For example, the frequency of very heavy rainfall above 2010 mm / hr in the 10s was about 2000% higher than in the 25s.

　Furthermore, as a result of analyzing the atmospheric flow during the rainy season for the last 20 years, the steam transport from the south along the eastern margin of the Pacific High was strengthened in the 2010s compared to the 2000s, and the subtropical jet. Two trends were noticeably observed: atmospheric waves were present on the stream, and troughs of pressure that strengthened the updraft were strengthened near the Baiu front.These changes in atmospheric flow appear to be related to the activation of Baiu front activity.

　This study suggests that the rainy season on the Baiu front is getting stronger on average, and it is thought that disaster prevention measures corresponding to that level of precipitation activity will be necessary in the future.In the future, continuous monitoring by rainfall observation satellites will be important.

Paper information:[Scientific Reports] Recent decadal enhancement of Meiyu-Baiu heavy rainfall over East Asia