The density, temperature, and punch head velocity are dominant factors to the variation of the compacted snow hardness measured by penetrometers. This effect is essential to the construction and operation of compacted snow roads. The Improved Motor-driven Snow Penetrometers (IMSP) are utilized in this research to control the penetration speed and measure the true cone hardness during snow penetration. This study employs a multi-method approach combining orthogonal experiments and the Support Vector Regression (SVR) technique to analyze the effects of these three factors on snow hardness. The results of this investigation indicate that, under identical conditions, density is positively correlated with the hardness of compacted snow, and its sensitivity and significance to the compacted snow hardness are the greatest. Temperature and penetration speed have an effect on hardness, which cannot be completely ignored. The hardness of snow close to its melting point, regardless of its density, decreases significantly at high penetration rates. This study investigates the factors that influence the hardness of compacted snow and provides substantial technical support for the design, construction, and maintenance of snow roads.

To study the snow microstructure at various metamorphism times and extract the snow neck area, a constant density (200 kg/m³) snow metamorphism experiment was conducted. The findings show that the neck region is mostly influenced by temperature, sun radiation, snow density and specific humidity, with wind speed having little effect. Additionally, we developed a multiple linear regression equation for the neck area under atmospheric forcing: “S = 288T + 2E + 189ρ + 12,194V − 20,443RH − 42,729”. This equation accounts for solar radiation (E), temperature (T), snow density (ρ), specific humidity (RH) and wind speed (V). Notably, the above five factors can account for 84% of the factors affecting the neck area, making it a crucial factor. The relationship between snow hardness and neck area is correlated at 71%, and in later stages of metamorphism, the correlation may increase to 91%. Based on the neck area, the following hardness value prediction is made: “H = 0.002764S + 67.922837”. This study documents the growth variations in the neck region of the metamorphic snow cover and elucidates the process by which outside factors impact the microstructure and macroscopic physical characteristics of the snow cover.

In their natural state, snow crystals are influenced by the atmosphere during formation and multiple factors after landing, resulting in varying particle sizes and unstable particle morphologies that are challenging to quantify. The current research mainly focuses on the relationship between the porosity of compacted snow samples or qualitatively describes snow crystals and their macroscopic physical properties, ignoring that the significant differences in the morphology of snow crystals also affect their physical properties. To quantitatively evaluate the morphology of snow crystals, we employed optical microscopy to obtain digital images of snow crystals in Harbin, utilizing the Sobel and Otsu algorithms to determine the equivalent particle size and fractal dimension of individual snow particles. In addition, the hardness of snow with a density of 0.4 g/cm³ was measured through a penetration test, with an analysis of its correlation relative to particle size and fractal dimension. The results indicated the fractal dimension as an effective parameter for characterizing particle shape, which decreased rapidly over time and then fluctuated within the range of 1.10 to 1.15. During the initial period, natural snow crystals broke down rapidly, leading to an increase in the percentage of natural snow crystals with an equivalent particle size of 0.2–0.4 mm up to 51.86%. After three days, the sintering effect between snow crystals was enhanced, resulting in an even distribution of the equivalent particle size. Finally, multiple linear regression analysis showed a positive correlation between compacted snow hardness and fractal dimension, with a negative correlation between compacted snow hardness and equivalent particle size. These findings offer valuable technical support and data reference for exploring the relationship between snow’s mechanical properties and its microscopic particle shape.

Under global warming, lateral melting plays an increasingly important role in heat exchange between ice and water. However, field-based observations of its depth-dependent behavior remain limited, hindering the development of reliable parameterizations. To address this, we performed continuous in situ measurements of lateral melting at Lake Hanzhang. Lateral melting rates at depths of 10, 20, 30, and 35 cm during the melt period were measured and analyzed. Total lateral melt amounts over the observation period were 64 mm at 10 cm, 84 mm at 20 cm, 148 mm at 30 cm, and 176 mm at 35 cm, revealing a pronounced depth-dependent gradient. This gradient was accompanied by distinct vertical differences in ice temperature, with the upper layer responding more closely to air temperature and the lower layer to water temperature. With rising air temperatures from −12 °C to above-zero and water temperatures from 2 °C to 4 °C, the lateral melting rate increased from 2 mm·h⁻¹. A parameterization scheme linking the ice–water temperature difference to the lateral melting rate was developed for different air temperature regimes. Notably, observed lateral melting under sub-freezing air temperatures provides a reference for non-summer conditions. In addition, lateral melting accelerates ice thinning and open-water formation, which enhance heat absorption and ice transparency, thereby increasing water temperature and photosynthetically active radiation beneath the ice. These changes may promote primary productivity, supporting a potential linkage between lateral melting and the under-ice habitat environment. Collectively, the results offer a more realistic basis for parameterizing lateral melting in ice thermodynamic models.