Fluctuations of snow depth before AMeDAS in the foothill area of the Northern Japan Alps

Abstract

Meteorological observations by the Japan Meteorological Agency were made at points called local observatories in addition to meteorological stations, until the AMeDAS (Automated Meteorological Data Acquisition System) went into operation. At the local observatories, individuals and government offices entrusted by the Japan Meteorological Agency were observing manually. The total number of local observatory was larger than the number of observation points of the current AMeDAS, but due to the limitations of the uniformity of the accuracy of the observation data and the reporting speed, it was updated to the current AMeDAS. Since the foothill area of the Northern Japanese Alps is known as a heavy snowfall area, snow depth has been observed for a long time. Meteorological observation records at local observatories, are kept as a handwritten original book. We collected it as image data, read the data from the image and input it again as numerical data, and analyzed the fluctuation of the snow depth before the AMeDAS observation in the foothill area of the Northern Japan Alps. The observation period is different for each of the five points where the snow depth was observed for more than 20 years, but there is no tendency for the annual maximum snow depth to increase or decrease at any of the points. The winter temperature in heavy snow years is low, and the winter temperature in light snow years is high.