This paper describes the long-term trends of snow depth and snow period at 48 sites in snowy areas in Japan (Hokkaido, Tohoku, and Hokuriku) for 60 years from 1962 to 2021 in the winter season. The study uses newly defined annual average snow depth (AASD), in addition to annual maximum snow depth (AMSD) used in previous studies. We find gradual decreases in AASD at three sites in Hokkaido facing the Sea of Japan, one site in Hokkaido facing the Sea of Okhotsk, and six sites in Hokuriku facing the Sea of Japan. We also find gradual increases in AASD at four sites in Hokkaido facing the Pacific Ocean and one site in Tohoku facing the Pacific Ocean. We identify six new significant long-term trends of snow depths using the AASD, which does not contain several local and short-term peaks that affect the AMSD. The long-term trends of AMSD were 1.6 to 3.4 times larger than those of AASD. Thus, estimating the average snow depth conditions at a given site using AMSD can cause overestimated trends of average snow depth conditions in winter. We also examine the average AASD and AMSD for six snowy areas in Japan. We also discuss the effects of the winter average temperature and Arctic Oscillation (AO) index on AASD and AMSD, the long-term trends of the snow period, and the increase in winter temperature for decreasing the AASD and AMSD in Hokuriku, Japan. The method for calculating AASD is described in detail.

We conducted a vehicle starting experiments in which the drive wheels were inserted into a pit created on a compacted-snow road surface. For each type of vehicle, we determined the pit depth on the compacted-snow surface, which is the boundary between the occurrence and avoidance of stranding (the minimum pit depth for occurrence of stranding, d_sp). For heavy trucks and combination vehicles, separate experiments on vehicle starting were performed in order to elucidate the mechanism behind vehicle strandings. The results were used to determine the maximum depth of compacted-snow cover at which vehicles remained free from stranding (the maximum non-stranding snow depth, H_smax).

The following findings were obtained. d_sp was greater for four-wheel-drive passenger cars and combination vehicles, and was the smallest for 2-t front-engine rear-wheel-drive trucks. d_sp was greater when the vehicles were loaded. For heavy trucks, combination vehicles, and 2-t trucks, d_sp increased with drive wheel load. Additionally, d_sp was found to increase linearly with increase in the outer diameter of the drive wheel. For heavy trucks, d_sp did not necessarily decrease significantly when only the middle drive wheel (between the front wheel and the rear wheel) got stuck in the pit on the compacted-snow surface. In case of a semi-trailer stuck in the pit on the compacted-snow surface, d_sp for combination vehicles was markedly lower.

Our results lead to the determination of the value of H_smax, which is expected to be utilized as an index value for more adequately implementing preventive road closures and early snow removal.

Tateyama Hut of the University of Toyama is located on top of Mt. Jodo (height 2839 m). Dew is often formed at an attic and on the floor of a storeroom: especially frost is formed in spring, and meltwater has a bad influence on a wooden building. Based on the measured temperature and humidity inside the hut, we try to find the cause of dew and frost condensation. In the summer, the temperature in the attic exceeded 30 °C and the humidity was 100 % during the day. To address this, we installed an extractor fan on the roof of the attic, which resulted in a decrease in humidity from saturation levels. Later, we set up an air supply and exhaust device with a sensible heat exchanger: dew dissolved in an attic and on the floor of a storeroom: and frost in the spring reduced. We report the time sequence of both temperature and humidity and discuss the effect of the air exchange system.