Natural Snowfall Research Articles

Snowfall Change Had Different Effects on Litter Decomposition for Two Typical Desert Species in Different Periods

In desert ecosystems, litter decomposition is the primary source of soil nutrients and is strongly affected by extreme climate events, which may influence desert plant survival and species diversity. To date, the effects of snowfall changes on litter decomposition in desert species remain poorly understood. Here, a snowfall manipulation experiment was conducted in Northwest China that included snowfall addition and removal treatments, as well as a natural snowfall control. Compared to the control, snowfall addition increased the amount of litter mass lost for Salsola passerina and Reaumuria soongarica during the snow-covered period by 21.54% and 21.8%, respectively. In contrast, snowfall addition effects differed between species during the snow-free period. More carbon was released from the S. passerina litter in the snowfall addition treatment during the snow-free period. Similarly, during the snow-covered period, more carbon and nitrogen were released from the R. soongorica litter in the snowfall addition treatment. Overall, the proportion of litter mass lost (from the annual total) increased with snowfall addition in the snow-covered period but was reduced with snowfall addition in the snow-free period. In the snow-covered period, the snowfall addition treatment affected litter mass loss to the same extent in both species but impacted S. passerina more strongly than R. soongorica in the snow-free period due to differences in soil urease activity. Changes in snowfall, therefore, significantly influenced litter decomposition in both desert species, but these effects differed between the snow-covered and snow-free period, particularly for litter with a higher C:N ratio.

Experimental study on the effect of nozzle configurations on snow quality for outdoor snow-makers

In regions with unfavorable climatic conditions and insufficient natural snowfall, skiing development depends significantly on the support of outdoor snow-makers. The atomized droplets produced by the swirl nozzle of the snow-maker collide with the crystal nucleus produced by the air-assisted atomizer to generate snowflakes. The effects of various configurations of swirl nozzles on snowmaking efficiency and snow quality are notably significant. This study investigates the influence of nozzle number, nozzle diameter, and ambient temperature on snowmaking performance through an outdoor snowmaking experiment. The results indicate that an appropriate nozzle configuration (number and diameter) significantly enhances snow quality. The spatial uniformity of snow density is significantly enhanced when utilizing 24 nozzles with a diameter of 1.9 mm and 72 mixed-diameter nozzles. With a nozzle diameter of 1.7 mm, the snow production of 48 and 80 nozzles is comparable; however, the water consumption of 48 nozzles is lower. Furthermore, at low temperatures, the artificial snow produced by the mixed-diameter nozzles exhibits snow quality characteristics comparable to those produced at high temperatures. Nevertheless, snow production is lower than that of the single-diameter nozzle configuration. Simultaneously, the density of the artificial snow produced at high temperatures is generally greater than that produced at low temperatures. Experimental measurements of the grain size of the artificial snow are concentrated between 0.15 and 0.55 mm. This study provides a basis for regulating snow quality in ski resorts. Additionally, it offers guidance on the design and structuring of efficient snow-makers.

Construction of a quantitative model for ski resort water demand and preliminary exploration of drainage irrigation pathways

In China, natural snowfall is insufficient, and ski resorts often require artificial snowmaking in winter and turf management in summer, which results in high overall water consumption and considered as one of the high water-consuming service industries, with an urgent need for theoretical foundations related to water management. Based on life cycle theory, we examined the characteristics of the water systems of ski resorts in winter and summer. A Monte Carlo simulation was used to construct a stochastic model to quantify the theoretical water consumption for snowmaking at ski resorts and to investigate the mechanisms by which various factors influence this consumption. We summarize the necessity of summer turf management and irrigation requirements at ski resorts, explore the interaction between ski resorts and agricultural irrigation. The results show that the theoretical water demand of ski resorts is basically consistent with the actual water consumption of ski resorts, that the constructed model is feasible, and that snowmaking water is the most important water use of ski resorts. Exploring the collection and reuse of meltwater or rainwater from ski resorts for agricultural irrigation in the spring and summer could provide more possibilities for the sustainable management of regional water resources. The research findings can provide a theoretical basis for scientifically and reasonably setting the norm of water intake for ski resorts and for developing comprehensive water resource management plans for ski resorts and agricultural irrigation.

A complete environmental wind tunnel for studying the evolution of snow accumulations under the effects of wind, rain, and heat

Given the escalating frequency of extreme cold weather worldwide, snow-induced building failures have increased substantially, especially in large-span space structures. The reason for engineering accidents lies in a lack of understanding of the intricate process of the mechanism of full-period evolution of snow “accumulation-melt-crystallization- accumulation” under the coupling actions of wind, rain, and heat. It is significant to develop a comprehensive and accurate environmental wind tunnel for conducting snow-relevant experiments under the multi-factors, which are barely studied. Hence, this paper proposes and establishes an experimental system called “Simulator of Natural Action of Wind-Rain-Heat-Snow for Space Structures (SNOW).” The system consists of an atmospheric boundary layer cryogenic wind tunnel subsystem, snowfall simulation subsystem, rain simulation subsystem, solar and building heating simulation subsystem, and high-precision multi-task monitoring and control subsystem. The facility can provide a 0–20 m/s stable wind field, −15 °C–0 °C low-temperature conditions, and a 2 m × 2 m experimental section. The calibrations of each subsystem were conducted in SNOW to ensure each component can successfully provide basic conditions for snow-relevant experiments. The SNOW can accurately simulate the entire process of natural snowfall and snow evolution under the coupling effects of wind, rain, and heat.

Response of soil microbial diversity and functionality to snow removal in a cool-temperate forest

Climate-induced changes in thinning snowpack can greatly impact soil freeze-thaw patterns and water supply. These effects may influence the soil microbial diversity and the key ecological functions mediated by microorganisms, thereby altering the cycling of nutrient in the ecosystem. A snow-exclusion experiment to explore the effects of snow removal on soil microbial diversity and functionality in Larix gmelinii forest. Control (natural snowfall), SR (complete snow removal) and SR-SR (complete snow removal, with snow returned for water supplementation at the end of winter) were represented three experimental treatments. The results showed that: snow removal resulted in more severe soil frost in winter. Soil nitrogen availability was higher in the snow removal plots compared to control plots in freeze-thaw period. Fungal diversity was not affected by snow removal, neither the α diversity of bacteria. However, snow removal did alter the bacterial community structure. These changes of the above did not persist into the growing season. SR-SR significantly reduced soil multifunctionality during freeze-thaw period, whereas SR did not. However, SR and SR-SR resulted in significantly higher soil multifunctionality than was observed in control during early growing season. Additionally, a widespread increase in the abundance of nitrogen cycling genes was observed in the SR and SR-SR plots during the freeze-thaw period and the early growing season, respectively. Snow removal significantly affected soil multifunctionality, which can be explained by changes in the microbial biomass, bacterial community structure and network complexity. Furthermore, snow removal significantly altered soil water content, temperature, and dissolved carbon, nitrogen. dbRDA and random forest analysis showed that soil water content, temperature, and total nitrogen as drivers of soil microbial community structure and multifunctionality. This study highlights that snow removal altered soil nitrogen availability, microbial community diversity, and multifunctionality during freeze-thaw period. However, these changes did not result in cross-seasonal legacy effects.

On the Radar Detection of Cloud Seeding Effects in Wintertime Orographic Cloud Systems

Abstract Recent studies from the Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) demonstrated definitive radar evidence of seeding signatures in winter orographic clouds during three intensive operation periods (IOPs) where the background signal from natural precipitation was weak and a radar signal attributable to seeding could be identified as traceable seeding lines. Except for the three IOPs where seeding was detected, background natural snowfall was present during seeding operations and no clear seeding signatures were detected. This paper provides a quantitative analysis to assess if orographic cloud seeding effects are detectable using radar when background precipitation is present. We show that a 5-dB change in equivalent reflectivity factor Ze is required to stand out against background natural Ze variability. This analysis considers four radar wavelengths, a range of background ice water contents (IWC) from 0.012 to 1.214 g m−3, and additional IWC introduced by seeding ranging from 0.012 to 0.486 g m−3. The upper-limit values of seeded IWC are based on measurements of IWC from the Nevzorov probe employed on the University of Wyoming King Air aircraft during SNOWIE. This analysis implies that seeding effects will be undetectable using radar within background snowfall unless the background IWC is small, and the seeding effects are large. It therefore remains uncertain whether seeding had no effect on cloud microstructure, and therefore produced no signature on radar, or whether seeding did have an effect, but that effect was undetectable against the background reflectivity associated with naturally produced precipitation. Significance Statement Operational glaciogenic seeding programs targeting wintertime orographic clouds are funded by a range of stakeholders to increase snowpack. Glaciogenic seeding signatures have been observed by radar when natural background snowfall is weak but never when heavy background precipitation was present. This analysis quantitatively shows that seeding effects will be undetectable using radar reflectivity under conditions of background snowfall unless the background snowfall is weak, and the seeding effects are large. It therefore remains uncertain whether seeding had no effect on cloud microstructure, and therefore produced no signature on radar, or whether seeding did have an effect, but that effect was undetectable against the background reflectivity associated with naturally produced precipitation. Alternative assessment methods such as trace element analysis in snow, aircraft measurements, precipitation measurements, and modeling should be used to determine the efficacy of orographic cloud seeding when heavy background precipitation is present.

Snowmobiling and Climate Change: Exploring Shifts in Snowmobile Activity Using a Temporal Analogue Approach in Ontario (Canada)

The multi-billion-dollar snowmobile industry is predicated on natural snowfall and cold temperatures, with a near absence of research that examines industry response to climatic variability and change. Using a temporal analogue approach, this study examines 30 years of climate data (1989–2019), along with operational (grooming hours) and performance (permit sales) indicators, to provide insight into the vulnerability and adaptive capacity of the Ontario snowmobile industry in a medium (RCP4.5) and high (RCP8.5) mid-century (2046–2060) emission scenario. The results underscore important temporal and spatial variability across Ontario’s 16 snowmobile districts, indicating that snowmobilers are highly resilient to marginal conditions, changing districts and switching from seasonal to daily permits in response to warming temperatures. The findings from this study can inform risk assessments in other major snowmobile markets (e.g., Canada, Europe, USA), with future research needs discussed.

DEM analyses of mesoscopic failure mechanism and stress bearing mechanism of compacted snow subjected to unconfined compressive loading

In order to explore the mesoscopic failure mechanism and bearing mechanism of compacted snow under loading. First, the skeleton of dendritic snow crystal was constructed by 13 ice rigid sphere particles which are bonded together using a completed bond contact model. Second, a "falling snow method" was proposed and used to simulate the whole process of natural snowfall, i.e. snow generation, snow falling, snow deposition, and snow compaction. Third, the compacted snow sample was sintered at different temperatures with different times; in sintering process, the snow particles were bonded together by the completed bond contact model. Finally, after contact model parameter calibration by reported snow test results, the unconfined compression tests on the finished sintering snow were carried out and the mesoscopic failure mechanism and stress bearing mechanism were analyzed. Take the sintering temperature of −10 °C and finished sintering samples for example, the results show that the number of compacted snow bond breaks was mainly contributed by tension bond breaks. Meanwhile, with the increase of density, the ratio of bond breaks in tension and compression was higher. When the density was below 475 kg·m−3, the bond breakage was dominated by bending. While the density was above 475 kg·m−3, the bond breakage was mainly shearing. The contribution of the normal contact force to the total axial stress accounted for about 65% which was greater than that of the tangential contact force (ρ = 400 kg m−3). This study can provide support for the mesomechanical failure theory of compacted snow engineering, such as snow roads, compacted snow runways, and snow foundations.

Imaging-based 3D particle tracking system for field characterization of particle dynamics in atmospheric flows

A particle tracking velocimetry apparatus is presented that is capable of measuring three-dimensional particle trajectories across large volumes, of the order of several meters, during natural snowfall events. Field experiments, aimed at understanding snow settling kinematics in atmospheric flows, were conducted during the 2021/2022 winter season using this apparatus, from which we show preliminary results. An overview of the methodology, wherein we use a UAV-based calibration method, is provided, and analysis is conducted of a select dataset to demonstrate the capabilities of the system for studying inertial particle dynamics in atmospheric flows. A modular camera array is used, designed specifically for handling the challenges of field deployment during snowfall. This imaging system is calibrated using synchronized imaging of a UAV-carried target to enable measurements centered 10 m above the ground within approximately a 4 m $$\times$$ 4 m $$\times$$ 6 m volume. Using the measured Lagrangian particle tracks, we present data concerning 3D trajectory curvature and acceleration statistics, as well as clustering behavior using Voronoï analysis. The limitations, as well as potential future developments, of such a system are discussed in the context of applications with other inertial particles.

Rapid Warming in the Australian Alps from Observation and NARCliM Simulations

The Australian Alps are the highest mountain range in Australia, which are important for biodiversity, energy generation and winter tourism. Significant increases in temperature in the past decades has had a huge impact on biodiversity and ecosystem in this region. In this study, observed temperature is used to assess how temperature changed over the Australian Alps and surrounding areas. We also use outputs from two generations of NARCliM (NSW and Australian Regional Climate Modelling) to investigate spatial and temporal variation of future changes in temperature and its extremes. The results show temperature increases faster for the Australian Alps than the surrounding areas, with clear spatial and temporal variation. The changes in temperature and its extremes are found to be strongly correlated with changes in albedo, which suggests faster warming in cool season might be dominated by decrease in albedo resulting from future changes in natural snowfall and snowpack. The warming induced reduction in future snow cover in the Australian Alps will have a significant impact on this region.

Analyzing influences of snowfall on electric field at the interface of composite cross-arm with finite element method

The composite cross-arm was used in large numbers in power systems due to its safety and economic advantages. The interfaces were the weak link in the property of composite cross-arm. However, the influence of severe weather such as ice and snow on the interface property was not clear, which would bring potential risks to operation safety for composite cross-arm. To this end, the finite element method was used to study the characteristics of the electric field at the FRP-silicone rubber and FRP-RPUF interfaces under snowfall conditions in this paper. Firstly, the snow and snowmelt models of the composite cross-arm were established by combining the natural snowfall conditions and the classical snowed model, then the influence of snowed degrees, snowmelt stages and dry-band on the interfaces electric field was analyzed. The results show that the snow without melting basically does not change the interface electric field. During the snowmelt stages, the average electric field intensity of the FRP-silicone rubber interface increases and the maximum electric field intensity of the two interfaces decreases. The distortion of the interface electric field caused by the dry-band in the middle snowmelt stage is the most serious, at this time, the electric fields at FRP-silicone rubber interfaces reach a maximum of 14.72 kV/cm and 8.53 kV/cm respectively. When the length of dry-band reaches or exceeds the distance between the high-voltage fitting and the eighth large umbrella skirt, it basically no longer causes the distortion of interface electric field. Compared to the FRP-RPUF interface, the FRP-silicone rubber interface is more severely affected by snowfall. The results can provide a reference for improving the interface property and ensuring the safety of the composite cross-arm in severe weather conditions.

Experiments on snowdrifts around two adjacent cube models based on a combined snow-wind facility

This study conducted experiments on the wind-induced snow drifting around two adjacent cube models, using artificial snow in an open air snow-wind combined experimental facility constructed at the Harbin Institute of Technology (HIT). In particular, 20 experiments were conducted on two adjacent cubes with three different wind directions, three different wind speeds, and four different spacings. They were compared with contrast experiments with a single cube under the same inflow condition. The cube models were two wooden cubes having dimensions of 0.5 × 0.5 × 0.5 m. The drift process of natural snowfall was simulated by scattering snow particles. After snowfall for 25 min in each experiment, the snowdrifts were measured by surveying approximately 300 points around the cubes. Contour maps of the normalized snow depths were drawn and analyzed. The experiments show that the wind direction and speed have a certain influence on a snowdrift. Based on the wind-snow movement mechanism, the relationship between the snowdrift pattern around two cubes and the snowdrift pattern around a single cube was explored. Under the same condition, the snowdrift pattern around the multiple cubes can be deduced from the snowdrift pattern around the single cube. The snowdrift pattern around the downstream cube depends on its spatial position relative to the upstream cube. Moreover, the snowdrift between two adjacent cubes seems to be dependent on a funneling effect.

Characterization of atmospheric coherent structures and their impact on a utility-scale wind turbine

Atmospheric turbulent velocity fluctuations are known to increase wind turbine structural loading and accelerate wake recovery, but the impact of vortical coherent structures in the atmosphere on wind turbines has not yet been evaluated. The current study uses flow imaging with natural snowfall with a field of view spanning the inflow and near wake. Vortical coherent structures with diameters of the order of 1 m are identified and characterized in the flow approaching a 2.5 MW wind turbine in the region spanning the bottom blade tip elevation to hub height. Their impact on turbine structural loading, power generation and wake behaviour are evaluated. Long coherent structure packets $(\mathrm{\ \mathbin{\lower.3ex\hbox{$\buildrel> \over {\smash{\scriptstyle\sim}\vphantom{_x}}$}}\ }200\;\textrm{m)}$ are shown to increase fluctuating stresses on the turbine support tower. Large inflow vortices interact with the turbine blades, leading to deviations from the expected power generation. The sign of these deviations is related to the rotation direction of the vortices, with rotation in the same direction as the circulation on the blades leading to periods of power surplus, and the opposite rotation causing power deficit. Periods of power deficit coincide with wake contraction events. These findings highlight the importance of considering coherent structure properties when making turbine design and siting decisions.

Super-large-scale flow visualization using natural snowfall for the study of utility-scale wind turbine flows

With the rapid growth of wind turbine installation in recent decades, fundamental physical understanding of the flow around wind turbines and farms is becoming increasingly critical for further efficiency increases. However, the effort to develop this understanding is hindered by the significant challenges involved in modelling such a complex dynamic system with a wide range of relevant scales (blade boundary layer thickness at ∼ 1 mm to atmospheric scales at ∼ 1 km). Additionally, conventional methods used to measure air flow around wind turbines in the field (e.g., lidar) are limited by low spatio-temporal resolutions.

Validation of model-based correction for non-Stokesian tracers

In-situ flow-tracking measurements at scales on the order of 10 m3 and larger remain a challenge. The large size of the tracers required for optical visibility results in an inertial lag and inherently low seeding density. For instance, natural snowfall, fake snow and soap bubbles on the order of 2 cm have been used as tracers for field measurements and extracted statistical quantities (Nemes et al., 2017; Wei et al., 2021; Rosi et al., 2014). There is also growing interest in networks of sensors for remote- measurement where optical access is impossible (Bolt et al. 2020; Villa et al. 2016). Onboard inertial measurement units (IMU) are a promising tool for high-resolution measurements over large spatial domains without optical access. However, due to the intrinsic lag, a dynamic-model-based correction is required for the tracking of transient phenomena, sketched in figure 1. In the present study, the tracer-velocity correction is evaluated by quantifying the residual error in measured flow velocity after the method of Galler et al. (2021) is applied.

Pan-European meteorological and snow indicators of climate change impact on ski tourism

Ski tourism plays a major socio-economic role in the snowy and mountainous areas of Europe such as the Alps, the Pyrenees, Nordic Europe, Eastern Europe, Anatolia, etc. Past and future climate change has an impact on the operating conditions of ski resorts, due to their reliance on natural snowfall and favorable conditions for snowmaking. However, there is currently a lack of assessment of past and future operating conditions of ski resorts at the pan-European scale in the context of climate change. The presented work aims at filling this gap, as part of the ”European Tourism” Sectoral Information System (SIS) of the Copernicus Climate Change Services (C3S). The Mountain Tourism Meteorological and Snow Indicators (MTMSI) were co-designed with representatives of the ski tourism industry, including consulting companies. They were derived from statistically adjusted EURO-CORDEX climate projections (multiple GCM/RCM pairs for RCP2.6, RCP4.5 and RCP8.5) using the UERRA 5.5 km resolution surface reanalysis as a reference, used as input to the snow cover model Crocus, with and without accounting for snow management (grooming, snowmaking). Results are generated for 100 m elevation bands for NUTS-3 geographical areas spanning all areas relevant to ski tourism in Europe. This article introduces the underpinning elements for the generation of this product, and illustrates results at the pan-European scale as well as for smaller scale case studies. A dedicated visualization app allows for easy navigation into the multiple dimensions of this dataset, thereby fulfilling the needs of a broad range of users.

Operational-dependent wind turbine wake impact on surface momentum flux

As wind energy continues to expand, increased interaction between wind farms and their surroundings can be expected. Using natural snowfall to visualize the air flow in the wake of a utility-scale wind turbine at unprecedented spatio-temporal resolution, intermittent periods of strong interaction between the wake and the ground surface are observed and the momentum flux during these periods is quantified. Significantly, two turbine operational-dependent pathways that lead to these periods of increased wake-ground interaction are identified. The first is caused by changes in tip speed ratio that lead to blade tip vortex leapfrogging, and the second results from increased power generation and the corresponding increase in tip vortex strength and wake expansion. Data from a nearby meteorological tower provides further insights into the strength and persistence of the enhanced flux for each pathway under different atmospheric conditions. Through the discovery of these pathways, discrepancies can be resolved between previous conflicting studies on the impact of wind turbines on surface fluxes. Furthermore, the results are used to generate a map of the potential impact of wind farms on surface momentum flux throughout the Continental United States, providing a valuable resource for wind farm siting decisions.

The effect of dynamic near-wake modulation on utility-scale wind turbine wake development

High-resolution field-scale experiments using flow visualization with natural snowfall and high-fidelity large eddy simulations are combined to investigate the effect of dynamic turbine operation and atmospheric conditions on wind turbine wake mixing and recovery in the wake of a 2.5 MW wind turbine. Instantaneous near-wake expansion and deflection in response to changes in blade pitch and wind direction, termed dynamic wake modulation, is quantified using both techniques, demonstrating excellent agreement. The simulations are used to extend these results by calculating the energy flux into the wake 7 rotor diameters downstream, showing that dynamic turbine-atmospheric interactions enhance mixing in the far-wake. This finding is exhibited under both uniform and turbulent inflow conditions. Under turbulent flow, a synergistic relationship is also observed between dynamic wake modulation and wake meandering, as wake recovery can be further accelerated when the two phenomena occur together. The results of this study have implications for the development of more realistic far-wake models that include the significant impact of dynamic wake modulation on wake mixing and development. Additionally, the findings from the current study can be used to develop advanced control algorithms to speed up wake breakdown and recovery, further improving wind farm efficiency.

An Experimental and Engineering Application of an Active Snow-Melting System for Highways Based on Heat-Pipe Technology

Major traffic accidents caused by snow cover and ice on pavements are responsible for large numbers of casualties and extensive property losses each year around the globe. A full-scale heat-pipe-based active snow-melting test system for outdoor asphalt roads was constructed to study and analyze its working performance on in-service asphalt highways. Based on long-term monitoring data, the active snow-melting system was analyzed to determine the temperature-field distribution pattern and relevant influencing factors as well as its performance on asphalt pavements. The research results show that: (1) the system exhibited excellent performance. Three natural snowfall events occurred on the full-scale test platform. In each event, the snow-melting system was able to effectively melt the snow. (2) Under long-term low-temperature conditions in winter, the active snow-melting system was able to increase the pavement temperature by approximately 10 °C. (3) In winter, the underground soil temperature decreased by approximately 4 °C as a result of heat extraction by the underground heat pipes and gradually recovered to its previous level as the outdoor ambient temperature gradually increased. This finding suggests that underground soil can provide heat to the snow-melting system for an extended period of time and continuously ensure its pavement snow-melting performance. The engineering application on the G18 Highway further demonstrates the effectiveness and reliability of active snow-melting systems based on heat-pipe technology.

Snow Reliability and Water Availability for Snowmaking in the Ski resorts of the Isère Département (French Alps), Under Current and Future Climate Conditions

This study presents the evolution of the snow reliability in the 24 alpine ski resorts of the Isère département (Northern French Alps, around Grenoble) over the last decades and its projection into the 21st century, taking into account grooming and snowmaking. The water demand for snowmaking is calculated and can be compared with hydrological simulations of water resource availability, under current and future climate conditions. Over the recent period, snowmaking has significantly improved the snow conditions in seasons with a natural snow deficit. For the middle of the 21st century, climate projections indicate that the expected evolution of snowmaking infrastructure by 2025 should make it possible to stabilize the snow reliability in seasons characterized by a deficit of natural snowfall. At a constant equipment rate, the evolution of water demand due to climate change is of the order of +15% on average in Isère between the recent period and the middle of the 21st century. The study shows that the pressure on water resources appears to not be the most critical point for the implementation of snowmaking, at the scale of the catchment basins in which the Isère ski resorts are located.