Journal of Natural Disaster Science

IDENTIFICATION OF LONG-TERM CLIMATIC VARIATIONS BASED ON TREE RING WIDTHS OF JAPANESE CYPRESSES

Tadanobu SATO
Associate Professor, Disaster Prevention Research Institute, Kyoto University
Atsushi YASHIMA
Research Associate, Disaster Prevention Research Institute, Kyoto University
and
Migaku TANAKA
Director, Nara National Cultural Properties Research Institute

(Received 10 October, 1989 and in revised form 20 December, 1989)

Abstract

We have developed a method by which to identify long-term climatic changes based on tree ring widths measured on Japanese cypresses. Ring width patterns were standardized by subtracting a spline function from the original pattern. The total number of rainy days occurring from April to September were calculated for a period of 170 years. This was made possible by combining data for rainy days which had appeared in diaries written in the Edo period (1603-1868) and data recorded by the Japan Meteorological Agency. We identified long-term climatic variations by use of an autoregressive moving average method. All the parameters in the proposed model were optimized by Kalman filter. Numerical results show the feasibility of using this newly developed method to identify climatic changes by means of ring width patterns.

Key words

Dendroclimatology, tree ring, number of rainy days, autoregressive moving average process, Kalman filter