Transparent ice without cloudiness caused by air bubbles is considered a high-quality ice and has high commercial value in the beverage industry. However, they cannot be easily obtained using the existing technologies. When necessary, only the transparent portions were removed from large ice blocks. Upon observing ice produced using the radiative ice-making technology developed by Kamimura et al., two types of bubbles were identified: “microbubbles” that form near the freezing surface in the early stage of the freezing process and “bubble columns” that start forming from specific locations during the ice formation process. This study focuses on bubble columns to understand their formation mechanisms and explore suppression methods. It was found that as ice grew, the concentration of dissolved gases in the water increased, and bubble columns appeared when it reached saturation. Based on this, a theoretical formula was derived to estimate the initial bubble formation location as a function of the initial dissolved-gas concentration. Using oxygen as a representative dissolved gas, experiments were conducted by varying the initial dissolved oxygen concentration in the source water and the cooling conditions. The results indicate that the trend of the observed initial bubble formation locations closely matched the predicted values from the theoretical formula, where the predicted value was greater than 40 mm. Furthermore, experiments were conducted by changing the growth rate by varying the radiative-cooling surface temperature. It was observed that under conditions of high growth rate, the discrepancies between the predicted and actual measurements increased.

In February 2025, an avalanche in Fukushima Prefecture was analyzed using Airborne Laser Scanning (ALS) to determine its quantitative morphological characteristics. The study found a small-scale, slab dry snow avalanche of the flow type. The site was a leeward slope influenced by strong westerly winds, with grass and shrub vegetation offering minimal avalanche suppression. A significant snowdrift, up to 10.0 m deep, was located near the initiation zone. The initiation zone had a slope of 40-45°, while the track and deposition zone were 20-25°, with an angle of elevation around 25°．The initiation zone was an elongated 150 m wide, and the track and deposition zone formed a slightly fan shape due to topography, with a flow length of 100-130 m. The avalanche’s overall appearance was rectangular. The initiation layer thickness reaching 4.0-9.0 m in some areas, with the 9.0 m attributed to the snowdrift. The avalanche involved the continuous collapse of the entire snowpack and surface layer across the 150 m width, with debris deposited as slabs directly below the initiation zone. Notable features included clear identification of initiation and stopping points and a long 76.6 m crack in the upper initiation zone, which remained uncollapsed, a rare occurrence given it is about half the avalanche's width.

During the winter of 2024/2025, record-breaking heavy snowfall occurred in the Tsugaru region of Aomori Prefecture, causing widespread power outages, traffic disruptions, and significant human, residential, and agricultural damage. As a result, the Disaster Relief Act was invoked on January 4, 2025. Heavy snowfall persisted, leading to the Disaster Relief Act being invoked again on February 25, 2025. Following the invocation of the Act in January, the authors conducted a wide-area snow survey focusing on urban areas in the Tsugaru region. The January survey revealed particularly high snow depths and snow water equivalents in the southwestern Tsugaru Plain and southern Aomori Plain. The average snow density across observation points was approximately 350 kg/m³, indicating dense, heavy, and wet snow, as confirmed by snow profile observations. Locations with significant increases in snow water equivalent from January to February corresponded to hilly areas where severe apple tree damage was reported.