Temperature trends in Japan: 1900-1996

摘要

Long-term trends in annual, seasonal, and monthly mean temperature (abbreviated as AMT, SMT, MMT, respectively) in Japan are investigated. The magnitude of a trend is measured by assuming it to be linear. The statistical significance of a site trend is assessed by the Mann-Kendall (MK) with consideration of serial correlation. The statistical field significance of trends in three major climatic regions: Hokkaido (Ⅰ), areas adjacent to the Japan sea (Ⅱ), and to the Pacific Ocean (Ⅲ), is evaluated by the bootstrapping test which preserves cross-correlation among sites. From 1900 to 1996, AMT increased from 0.51 to 2.77℃ averaged across all 46 sites. At the regional scale, AMT increased by 1.38, 1.08, and 1.32℃ in regions Ⅰ, Ⅱ, and Ⅲ, respectively. The trends at both sites and regions are statistically significant even at the significance level (α) of 0.005. SMT increased from 0.47 to 3.69℃ at all the 19 available sites with the highest increases in winter and spring. Except for a few series, the changes in SMT are statistically significant at α = 0.01. The upward trends in SMT are statistically significant even at α = 0.001 in both regions Ⅱ and Ⅲ. MMT at 19 sites increased within a wide range from 0.17 to 4.12℃. The increases are largest in the winter and spring months, and most of the site increases are statistically significant at α = 0.05. The trends are statistically significant at α = 0.025 and 0.001 in regions Ⅱ and Ⅲ, respectively. The trends in both SMT and MMT in region Ⅲ are larger than those in region Ⅱ.