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Numerical simulation of drifting snow sublimation in the saltation layer.

Dai X, Huang N - Sci Rep (2014)

Bottom Line: Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow.In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer.Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000, China.

ABSTRACT
Snow sublimation is an important hydrological process and one of the main causes of the temporal and spatial variation of snow distribution. Compared with surface sublimation, drifting snow sublimation is more effective due to the greater surface exposure area of snow particles in the air. Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow. In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer. The simulated results show 1) the average sublimation rate of drifting snow particles increases linearly with the friction velocity; 2) the sublimation rate gradient with the friction velocity increases with increases in the environmental temperature and the undersaturation of air; 3) when the friction velocity is less than 0.525 m/s, the snowdrift sublimation of saltating particles is greater than that of suspended particles; and 4) the snowdrift sublimation in the saltation layer is less than that of the suspended particles only when the friction velocity is greater than 0.625 m/s. Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation.

No MeSH data available.


Related in: MedlinePlus

Changes in the sublimation rate of drifting snow with time and friction velocity (u*ranges from 0.25 m/s to 0.5 m/s) under varying environmental conditions (Temperature of 263.15 K or 268.15 K and relative humidity of 0.3 or 0.8).
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f1: Changes in the sublimation rate of drifting snow with time and friction velocity (u*ranges from 0.25 m/s to 0.5 m/s) under varying environmental conditions (Temperature of 263.15 K or 268.15 K and relative humidity of 0.3 or 0.8).

Mentions: In wind-blown snow, snow particles are entrained and transported by the wind, while the wind field is simultaneously influenced by the snow particles, indicating a self-regulating feedback mechanism between the saltating particles and the wind field. In this mechanism, the drag force associated with particle acceleration reduces the wind velocity in the saltation layer, thus limiting the entrainment of further particles21. At a given wind speed, the number of snow particles in the saltation layer initially increases rapidly with time and then decreases gradually until it reaches a steady state, i.e., the number of particles in the layer will not increase further. The time for the wind-blown snow to reach steady state decreases as the friction velocity increases2122. Figure 1 shows the temporal evolution of DSS with different friction velocity (ranging from 0.25 m/s to 0.5 m/s) under different environmental conditions, with a temperature of 263.15 K or 268.15 K and humidity of 0.3 or 0.8. As shown in Figure 1, as time advances, the snowdrift sublimation rate first increases rapidly, then decays slightly, and finally approaches a dynamic steady state, consistent with the development processes of snow saltation. As the friction velocity increases, the time for snowdrift sublimation rate to reach the dynamic steady state decreases. For example, the time to steady state for the sublimation rate is approximately 2 s at a friction velocity of 0.25 m/s, whereas it is less than 1 s at a friction velocity of 0.5 m/s (Fig. 1a). Figure 1 also shows that with temperature and relative humidity held constant, the sublimation rate increases with friction velocity. A comparison of Figure 1a, 1b, 1c, and 1d clearly shows that the sublimation rate increases with increasing temperature with the relative humidity and friction velocity held constant. Similarly, the sublimation rate increases with decreasing humidity with the temperature and friction velocity held constant. The effects of environment conditions on the sublimation rate in our simulations are consistent with previous studies, i.e., DSS easily occurs at warmer temperatures and greater wind speeds23.


Numerical simulation of drifting snow sublimation in the saltation layer.

Dai X, Huang N - Sci Rep (2014)

Changes in the sublimation rate of drifting snow with time and friction velocity (u*ranges from 0.25 m/s to 0.5 m/s) under varying environmental conditions (Temperature of 263.15 K or 268.15 K and relative humidity of 0.3 or 0.8).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4196100&req=5

f1: Changes in the sublimation rate of drifting snow with time and friction velocity (u*ranges from 0.25 m/s to 0.5 m/s) under varying environmental conditions (Temperature of 263.15 K or 268.15 K and relative humidity of 0.3 or 0.8).
Mentions: In wind-blown snow, snow particles are entrained and transported by the wind, while the wind field is simultaneously influenced by the snow particles, indicating a self-regulating feedback mechanism between the saltating particles and the wind field. In this mechanism, the drag force associated with particle acceleration reduces the wind velocity in the saltation layer, thus limiting the entrainment of further particles21. At a given wind speed, the number of snow particles in the saltation layer initially increases rapidly with time and then decreases gradually until it reaches a steady state, i.e., the number of particles in the layer will not increase further. The time for the wind-blown snow to reach steady state decreases as the friction velocity increases2122. Figure 1 shows the temporal evolution of DSS with different friction velocity (ranging from 0.25 m/s to 0.5 m/s) under different environmental conditions, with a temperature of 263.15 K or 268.15 K and humidity of 0.3 or 0.8. As shown in Figure 1, as time advances, the snowdrift sublimation rate first increases rapidly, then decays slightly, and finally approaches a dynamic steady state, consistent with the development processes of snow saltation. As the friction velocity increases, the time for snowdrift sublimation rate to reach the dynamic steady state decreases. For example, the time to steady state for the sublimation rate is approximately 2 s at a friction velocity of 0.25 m/s, whereas it is less than 1 s at a friction velocity of 0.5 m/s (Fig. 1a). Figure 1 also shows that with temperature and relative humidity held constant, the sublimation rate increases with friction velocity. A comparison of Figure 1a, 1b, 1c, and 1d clearly shows that the sublimation rate increases with increasing temperature with the relative humidity and friction velocity held constant. Similarly, the sublimation rate increases with decreasing humidity with the temperature and friction velocity held constant. The effects of environment conditions on the sublimation rate in our simulations are consistent with previous studies, i.e., DSS easily occurs at warmer temperatures and greater wind speeds23.

Bottom Line: Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow.In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer.Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000, China.

ABSTRACT
Snow sublimation is an important hydrological process and one of the main causes of the temporal and spatial variation of snow distribution. Compared with surface sublimation, drifting snow sublimation is more effective due to the greater surface exposure area of snow particles in the air. Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow. In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer. The simulated results show 1) the average sublimation rate of drifting snow particles increases linearly with the friction velocity; 2) the sublimation rate gradient with the friction velocity increases with increases in the environmental temperature and the undersaturation of air; 3) when the friction velocity is less than 0.525 m/s, the snowdrift sublimation of saltating particles is greater than that of suspended particles; and 4) the snowdrift sublimation in the saltation layer is less than that of the suspended particles only when the friction velocity is greater than 0.625 m/s. Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation.

No MeSH data available.


Related in: MedlinePlus