Geographical review of Japan series B Vol. 89(2016) No. 2

Many natural disasters have occurred in Japan since ancient times. It corresponds to the “Medieval climate anomaly (MCA)” or “Medieval warm period (MWP)” which existed from the 9th to the 12th centuries, as pointed out by the climatologists in Europe and U.S.A. In the history of Japan, however, this period is called “ancient period”. In this study, the authors collected 1,220 records of climatic disasters and constructed a chronology of climatic disasters in Japan from the 7th to the 12th centuries. Furthermore, their secular changes of kinds and regions were clarified. It can be said that number of climatic disasters increased remarkably during the second half of the 9th century, the early 11th century and the latter half of the 12th century. Concerning kinds of climatic disasters, the most common disaster was storm (26.1%) and the next was drought (19.8%). As for place names related to all climatic disasters, the most frequent place was Kyoto (48.3%) and the second was Nara (7.9%). From these investigations, it was clarified that drought was the major climatic disaster before the 9th century. On the other hand, disaster caused by too much rain prevailed from the 9th century. But the regions with records on climatic disasters clearly changed from Nara to Kyoto at the end of the 8th century. Therefore, the authors proposed that local climates in Nara and Kyoto influenced the change of climatic disasters.