Empirical Study on the Conditions for Blowing Snow Events at Roads on High-Altitude Mountains

Blowing snow is a typical natural hazard in high-altitude and snow-prone regions, and its impact could be significantly reduced by accurate forecasts. The empirical study on the conditions for blowing snow hazards on the Sichuan–Xizang Highway in high-altitude mountainous areas are conducted in this paper. The study reveals that blowing snow events primarily occur from December to the following February, with the affected roads mainly located in mountainous areas above altitudes of 3000 m. Based on physical characteristics, snow cover is categorized into three types with different processes of snowdrifts: newly fallen or wind-transported snow, slightly consolidated snow, and compacted snow undergoing freeze–thaw cycles, each exhibiting distinct snowdrift formation processes. Field measurement results indicate that the average threshold wind speeds for initiating blowing snow are 9.65, 14.77, and 23.15 m s⁻¹ at the 10-m height for these three snow types, respectively. Additionally, analyzing the effects of temperature and snowfall timing on threshold wind velocity, a multi-tiered susceptibility model for blowing snow is developed. This model offers enhanced practical applicability for classifying different types of snow and provides more detailed insights into the variations in threshold wind speed during both the early and later stages of snowfall events, compared to models that rely solely on constant thresholds or temperature-based criteria.