Secular Changes of the Bai-u Season in Japan

Abstract

The Bai-u season between the beginning of the eighteenth century and 1895 was reconstructed with the aid of weather records entered in old diaries. Long-term tendencies and periodicities of the Bai-u season were investigated by linking the reconstructed data to that of an instrumentally observed time. Generally speaking, with regard to its beginning, end and duration, there are no significant differences between the Bai-u season in the historical time and in the instrumental time. Thus, the implication is that the characteristics of the Bai-u season in the Little Ice Age were the same as those in the post-Little Ice Age. The duration of the Bai-u season revealed a strong positive correlation with the end of the Bai-u season in both the historical and the instrumental time. The time series of the end and the duration of the Bai-u season indicated a longer cycle of around sixty years. It was also observed that three great famines were associated with late endings of the Bai-u season. In particular, the Tohoku District was adversely affected by cool summers during the years when the end of the Bai-u season was late. © 1987, The Association of Japanese Geographers. All rights reserved.