Long-term hourly data records of the Automated Meteorological Data Acquisition System (AMeDAS) with snow depth measurements at three high elevation sites were analyzed in central Japan to assess the decadal scale winter climate variabilities with the effects of observation biases. Year-to-year variations of persistent snow cover periods (PSCPs) did not show a significant shortening trend with the delays of starting the PSCP associated with El Niño in December and forward to the ending of the PSCP with nationwide warming in March. Significant warming trends in the surface air temperature averaged in PSCPs were not identified, and length of the PSCP strongly contributed to the year-to-year variations of monthly averaged winter air temperatures. Long-term variabilities of precipitation records were primarily affected by changing the gauge type and data resolutions. After a simple correction of gauge undercatch by air temperature and wind speed, the amount of precipitation increased by around 20 % at the northern station but only by 3 % in the south due to frequent rain-on-snow events. In the two northern stations, snowfall amounts on the order of around 10 % were estimated to be missing in the precipitation records, where a long-term decreasing trend in occurrences of freezing precipitation was also found. The statistics calculated by AMeDAS data were verified using the data of the Vaisala Present Weather Detector in the Sugadaira Highland.

　　Snow algae are photosynthetic microbes growing on snowpacks and are commonly observed in mountain areas in Japan. In this study, we report the snow algal blooms observed in Mt. Echigo-Komagatake located in Niigata prefecture, Japan. Field investigation was conducted in late June of 2021 on a snow patch located in an alpine zone at an altitude of 2000 m above sea level. Patches of snow with red, green, or brown color were observed on the snowpack. Microscopic observation showed that the colored snow contained various morpho-types of snow algal cells, which appeared to be similar to those previously reported in Japan. The algal communities of the colored snow were mostly dominated by red spherical cells, which is likely to be Sanguina nivaloides, and consistent with those of the red snow reported in other alpine snowpacks in Japan. However, some samples showed a community consisting of various cell types, including multiple species of genus Chloromonas. The difference in community structure may be due to distance from vegetation around the snow patch, nutrient conditions of the snow, and/or growth period of the algae. The snow algal blooms of Mt. Echigo-Komagatake can be characterized by the appearance of various colors and algal communities on a snowpack.