Yukihiro KITA

Fourier Analysis Using Winter Temperature Observations through 25 years at Nagaoka

Toshiro KUMAKURA

It has been important to understand meteorological characteristics of heavy snowfall and light snowfall to prevent snow disasters. Especially, as one of the meteorological factors, snowfall and snowmelt along the coast of the Japan Sea particularly depend on the temperature. Therefore, in these regions along the coast of the Japan Sea, it should be extremely important to understand the cycle characteristics of temperature variability. We estimated the cycle characteristics in winter by using Fourier analysis using the temperature data of the past 25 years in Nagaoka and separating them into 8 years as heavy snowfall period and 17 years as light snowfall period. The three results are as follows : (1)The change of the temperature from 4 days cycle to 14 days cycle is by 0.48�� in light snowfall years and is by 0.62�� in heavy snowfall years. (2)In 7.4 days cycle considered as the turning point of cold air and warm air, the change of the temperature is by 0.56�� in light snowfall years and is 0.62�� in heavy snowfall years. (3)Compared to light snowfall years, there is a larger difference in heavy snowfall years between the average temperature change and the change lead by cold air and warm air .It is thought that there can be a risk of intensive snowfall caused by cold air and avalanche caused by warm air.