Abstract
Drifting snow is a significant factor in snow redistribution and cascading snow incidents. However, field observations of drifting snow are relatively difficult due to limitations in observation technology, and drifting snow observation data are scarce. The FlowCapt sensor is a relatively stable sensor that has been widely used in recent years to obtain drifting snow observations. This study presents the results from two FlowCapt sensors that were employed to obtain field observations of drifting snow during the 2017–2018 snow season in the southern Altai Mountains, Central Asia, where the snow cover is widely distributed. The results demonstrate that the FlowCapt sensor can successfully acquire stable field observations of drifting snow. Drifting snow occurs mainly within the height range of 80-cm zone above the snow surface, which accounts for 97.73% of the total snow mass transport. There were three typical snowdrift events during the 2017–2018 observation period, and the total snowdrift flux caused during these key events accounted for 87.5% of the total snow mass transport. Wind speed controls the occurrence of drifting snow, and the threshold wind speed (friction velocity) for drifting snow is approximately 3.0 m/s (0.15 m/s); the potential for drifting snow increases rapidly above 3.0 m/s, with drifting snow essentially being inevitable for wind speeds above 7.0 m/s. Similarly, the snowdrift flux is also controlled by wind speed. The observed maximum snowdrift flux reaches 192.00 g/(m2·s) and the total snow transport is 584.9 kg/m during the snow season. Although drifting snow will lead to a redistribution of the snow mass, any accumulation or loss of the snow mass is also affected synergistically by other factors, such as topography and snow properties. This study provides a paradigm for establishing a field observation network for drifting snow monitoring in the southern Altai Mountains and bridges the gaps toward elucidating the mechanisms of drifting snow in the Altai Mountains of Central Asia. A broader network of drifting snow observations will provide key data for the prevention and control of drifting snow incidents, such as the design height of windbreak fences installed on both sides of highways.
Highlights
Half of the land surface in the Northern Hemisphere, or 4.5 × 107 km2, is covered by snow in winter, with ~3062 × 109 tons of average annual snowfall contributing to this extensive snow cover [1,2]
TST = ∑ 600 × [SDF01i × (L − SDi) + SDF12i × L] i=1 where L was the length of the FlowCapt tube (1 m), SDF01, SDF12 and SD were the snowdrift flux observed by the lower and upper FlowCapt sensors and snow depth at the i-th 10-min interval
Drifting snow mainly occurred within 80 cm of the snow surface
Summary
Half of the land surface in the Northern Hemisphere, or 4.5 × 107 km, is covered by snow in winter, with ~3062 × 109 tons of average annual snowfall contributing to this extensive snow cover [1,2]. Snow fences are installed on both sides of roads as an effective mitigation tool, reducing the impact of drifting snow on traffic by decreasing the wind speed and capturing more snow on the lee side of the barrier or fence [17] This redistribution due to drifting snow may result in spatial heterogeneities in the meltwater resources across the steppe region, which will exacerbate spatial heterogeneities in vegetation by altering the hydrothermal conditions of the soil [18]. Snow incidents, including snowstorms, drifting snow, and snowmelt floods, are the dominant disasters in northern Xinjiang [44], whereas drifting snow is the most frequent and serious disaster in the Altai and Tien mountains due to the low snow density and liquid water content in the regional snow cover [10,43], which facilitates the movement of snow particles. Effective mitigation of the impact of snowstorms and drifting snow on traffic is critical for ensuring traffic safety and efficient operations in the areas surrounding the Altai and Tien mountains
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