Abstract
The trends in annual mean air temperature and seasonal mean air temperature fluctuations using the data from high-elevation areas of the central mountainous region were analyzed. The annual mean air temperatures at 12 observation sites showed synchronized high and low air temperature years. In the high-altitude areas of the central mountainous region, year-to-year differences in annual mean air temperature between locations were not significant. However, the trends in annual mean air temperature fluctuations differed from location to location. The rate of increase in annual mean air temperature at each location and the tau value of the Mann-Kendall test showed a strong correlation with the number of years for which annual average air temperature was calculated at each location. The longer the observation period, the weaker the increase trend in annual mean air temperature; conversely, the shorter the observation period, the more statistically significant the increase trend in annual mean air temperature. In the analysis of fluctuation trend for winter mean air temperature, neither increase nor decrease trends were statistically significant at all sites. On the other hand, the seasonal mean air temperatures for spring, summer, and autumn showed an increase trend at many locations. In the relationship between the tau value (a result of the Mann-Kendall test for seasonal mean air temperature fluctuations) and elevation at each site, there is no statistically significant correlation for winter and spring, but a statistically significant correlation is observed for summer and autumn at all sites except one site. For both summer and autumn, the recent increase trend in seasonal mean air temperature is more pronounced at lower elevation.
