Snow Drift Research Articles

Physics and geochemistry of lakes in Vestfjella, Dronning Maud Land

AbstractShallow Antarctic surface lakes belong to the most extreme aquatic environments on the Earth. In Vestfjella, proglacial surface lakes and ponds are characterized by a 2–5 month long period with liquid water and depths < 2 m. We give a detailed description of nine seasonal lakes and ponds situating at three nunataqs (Basen, Plogen and Fossilryggen) in western Dronning Maud Land. Their physical and geochemical properties are provided based on observations in four summers. Three main ‘lake categories‘ were found: 1) supraglacial lakes, 2) epiglacial ponds and 3) nunataq ponds. Category 3 lakes can be divided into two subgroups with regards to whether the meltwater source is glacial or just seasonal snow patches. Supraglacial lakes are ultra-oligotrophic (electrical conductivity < 10 μS cm−1, pH < 7), while in epiglacial ponds the concentrations of dissolved and suspended matter and trophic status vary over a wide range (electrical conductivity 20–110 μS cm−1, pH 6–9). In nunataq ponds, the maxima were an electrical conductivity of 1042 μS cm−1 and a pH of 10.1, and water temperature may have wide diurnal and day-to-day fluctuations (maximum 9.3°C) because snowfall, snow drift and sublimation influence the net solar irradiance.

AN ASSESSMENT OF THE SIMILARITY OF SNOWSTORM AVALANCHING IN THE KHIBINY MOUNTAINS

In practice, forecasting of avalanche occurrences in a single avalanche path is usually subjective based on background avalanche and weather forecasts, data on the location and topography of the avalanche starting zone, as well as available data on the snowpack in it. Moreover, forecasters sometimes identify avalanche starting zones, in which, according to their opinion, avalanche formation is similar. It is generally believed that avalanche formation occurs similarly in avalanche starting zones similar in morphology and morphometry, as well as having similar exposure. The aim of the work was to establish a quantitative relationship in the avalanche formation of snowstorm avalanches in 22 avalanche starting zones located in an area of about 25 km2 located in the southern part of the Khibiny Mountains. The study was based on long-term observations of avalanches in this area. As a measure of the proximity of avalanche formation in two avalanche starting zones P (i / j), we used the conditional probability of avalanche formation in avalanche starting zone i, if an avalanche formed in avalanche starting zone j. As the study showed, correlations between avalanche formation in various avalanche starting zones are statistically significant, but, as a rule, rather weak. The most similar formation of snow avalanches occurs in the starting zones having a similar exposure. In addition, the deformations of the air flow in the mountain system and the size of the snow drift zones, as well as the spatial variability of the physical and mechanical characteristics of snowpack in avalanche starting zones, also affect. A methodology for probabilistic diagnosis and forecasting of snowstorm avalanches using avalanche starting zones-indicators is proposed.

Wind Tunnel Tests and Numerical Simulations of Wind‐Induced Snow Drift in an Open Stadium and Gymnasium

A long‐span sports centre generally comprises multiple stadiums and gymnasiums, for which mutual interference effects of wind‐induced snow motion are not explicitly included in the specifications of various countries. This problem is addressed herein by performing wind tunnel tests and numerical simulations to investigate the snow distribution and mutual interference effect on the roofs of long‐span stadiums and gymnasiums. The wind tunnel tests were used to analyse the influences of the opening direction (0°, 90°, 180°, and 270°) and spacing (0.3 L, 0.5 L, 1 L, 1.5 L, 2 L, and 2.5 L, where L is the gymnasium span) of the stadium and gymnasium. The wind tunnel tests and numerical simulations were used to analyse the influence of the wind direction angle (from 0° to 315°, there are a total of eight groups in 45° intervals). The following results were obtained. The stadium opening had a significant effect on the snow distribution on the surface of the two structures. An even snow distribution was obtained when the stadium opened directly facing the gymnasium, which corresponded to the safest condition for the structures’ surfaces. As the spacing between the buildings increased, the interference effect between the two structures was reduced. The interference was negligible for a spacing of 2 L. The stadium had the most significant amplification interference effect on the gymnasium for a wind direction angle of 45°, which was extremely unfavourable to the safety of the structure. The most favourable wind direction angle was 270°, where there were both amplification interference and blockage interference.

Continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on an alpine glacier

Abstract. Snow water equivalent (SWE) measurements of seasonal snowpack are crucial in many research fields. Yet accurate measurements at a high temporal resolution are difficult to obtain in high mountain regions. With a cosmic ray sensor (CRS), SWE can be inferred from neutron counts. We present the analyses of temporally continuous SWE measurements by a CRS on an alpine glacier in Switzerland (Glacier de la Plaine Morte) over two winter seasons (2016/17 and 2017/18), which differed markedly in the amount and timing of snow accumulation. By combining SWE with snow depth measurements, we calculate the daily mean density of the snowpack. Compared to manual field observations from snow pits, the autonomous measurements overestimate SWE by +2 % ± 13 %. Snow depth and the bulk snow density deviate from the manual measurements by ±6 % and ±9 %, respectively. The CRS measured with high reliability over two winter seasons and is thus considered a promising method to observe SWE at remote alpine sites. We use the daily observations to classify winter season days into those dominated by accumulation (solid precipitation, snow drift), ablation (snow drift, snowmelt) or snow densification. For each of these process-dominated days the prevailing meteorological conditions are distinct. The continuous SWE measurements were also used to define a scaling factor for precipitation amounts from nearby meteorological stations. With this analysis, we show that a best-possible constant scaling factor results in cumulative precipitation amounts that differ by a mean absolute error of less than 80 mm w.e. from snow accumulation at this site.

Evaluation of SNODAS Snow Water Equivalent in Western Canada and Assimilation Into a Cold Region Hydrological Model

AbstractSnow water equivalent (SWE) is one of the most hydrologically important physical properties of a snowpack. The U.S. National Weather Service's Snow Data Assimilation System (SNODAS) provides snow products at high spatial (~1 km2) and temporal (daily) resolution for the contiguous United States and southern Canada. This study evaluated the SNODAS SWE product in the boreal forest, prairie, and Canadian Rockies of western Canada against extensive snow survey measurements. SNODAS was found to work well in sheltered environments, to overestimate SWE under needle‐leaf forests, and to be unable to capture the spatial variation of SWE in windswept prairie and alpine environments. Results indicate that SNODAS SWE accuracy is strongly influenced by the missing blowing snow redistribution and canopy energetics and snow interception and sublimation processes in the mass balance calculations of the SNODAS model and by erroneous precipitation data forcing the model. To demonstrate how errors caused by missing processes can be corrected in areas with low assimilation frequency, SNODAS data were assimilated into a physically based hydrological model created using the modular Cold Region Hydrological Modelling (CRHM) platform that includes blowing and intercepted snow redistribution and subcanopy melt energetic processes. This approach decreased the overestimation of SWE compared to SNODAS from 135 to 79% in the study area and suggests that snow assimilation modeled SWE quality can be improved if snow redistribution, sublimation, and subcanopy melt processes are incorporated.

On Equilibrium Properties of the Replicator\u2013Mutator Equation in Deterministic and Random Games

In this paper, we study the number of equilibria of the replicator–mutator dynamics for both deterministic and random multi-player two-strategy evolutionary games. For deterministic games, using Descartes’ rule of signs, we provide a formula to compute the number of equilibria in multi-player games via the number of change of signs in the coefficients of a polynomial. For two-player social dilemmas (namely the Prisoner’s Dilemma, Snow Drift, Stag Hunt and Harmony), we characterize (stable) equilibrium points and analytically calculate the probability of having a certain number of equilibria when the payoff entries are uniformly distributed. For multi-player random games whose pay-offs are independently distributed according to a normal distribution, by employing techniques from random polynomial theory, we compute the expected or average number of internal equilibria. In addition, we perform extensive simulations by sampling and averaging over a large number of possible payoff matrices to compare with and illustrate analytical results. Numerical simulations also suggest several interesting behaviours of the average number of equilibria when the number of players is sufficiently large or when the mutation is sufficiently small. In general, we observe that introducing mutation results in a larger average number of internal equilibria than when mutation is absent, implying that mutation leads to larger behavioural diversity in dynamical systems. Interestingly, this number is largest when mutation is rare rather than when it is frequent.

Origin and advances in implementing blowing-snow effects in the Community Land Model

Origin and advances in implementing blowing-snow effects in the Community Land Model

Timing and duration of hydrological transitions in Arctic polygonal ground from stable isotopes

AbstractLand surface models and Earth system models that include Arctic landscapes must capture the abrupt hydrological transitions that occur during the annual thaw and deepening of the active layer. In this work, stable water isotopes (δ2H and δ18O) are used to appraise hydrologically significant transitions during annual landscape thaw at the Barrow Environmental Observatory (Utqiaġvik, Alaska). These hydrologically significant periods are then linked to annual shifts in the landscape energy balance, deduced from meteorological data and described by the microclimatic periods: Winter, Pre‐Melt, Melt, Post‐Melt, Summer, and Freeze‐Up. The tight coupling of the microclimatic periods with the hydrological transitions supports the use of microclimatic periods as a means of linking polygonal surface water hydrology to meteorological datasets, which provides a mechanism for improving the representation of polygonal surface water hydrology in process‐based models. Rayleigh process reconstruction of the isotopic changes revealed that 19% of winter precipitation was lost to sublimation prior to melting and that 23% of surface water was lost to evaporation during the first 10 days post‐melt. This agrees with evaporation rates reported in a separate study using an eddy covariance flux tower located nearby. An additional 17% was lost to evaporation during the next 33 days. Stable water isotopes are also used to identify the dominant sources of surface water to various hydrogeomorphological features prevalent in polygonal terrain (a lake, a low centre polygon centre, troughs within the rims of low centre polygons, flat centre polygon troughs, a high centre polygon trough, and drainages). Hydrogeomorphologies that retained significant old water or acted as snow drifts are isotopically distinct during the Melt Period and therefore are easily distinguished. Biogeochemical changes related to the annual thaw are also reported and coupled to the hydrological transitions, which provides insight into the sources and sinks of these ions to and from the landscape.

雪粒子の空気輸送モデルによる地吹雪メカニズムの解明 －その5 間欠性から連続性への輸送形態の変化－

雪粒子の空気輸送モデルによる地吹雪メカニズムの解明 －その5 間欠性から連続性への輸送形態の変化－

Investing the effect of age and cooperation in spatial multigame

In practice, cooperation is widely observed in various systems, including social and biological ones;nevertheless, it seems to be apparently in conflict with the natural selection Recently, spatial multi-games are investigated by numerous scholars aiming to ensure the benefits of cooperative behaviors. Hence in this manuscript, a multi-game consisting of the prisoner’s (PD) game and snow drift (SD) game, is mainly considered. Here, the aging property is incorporated aiming to evaluate the effect of age on cooperation in the investigated spatial multi-game . Numerous simulations are then performed with corresponding results being provided. We find that frequencies of cooperation can be improved by a large extent with the incorporation of the evolutionary mechanism introduced in this manuscript. Finally, we also find an interesting phenomenon, i.e., when the threshold θ=5 and θ=60, the individuals’ age in the system seems to obey uniform distribution. Whereas for θ=20 and θ=40, corresponding distribution seems to follow power law distribution. Eventually, we hope that our founding in this manuscript can shed some lights on resolving the social dilemmas.

Aerodynamic Stability of Bridge Structures

Large-span bridges, which are flexible structures, are more susceptible to the wind influence. At the same time, it is necessary to take into account the effect of snow drift and automobile traffic on the stability of the superstructure. As the object of research a metal continuous beam bridge with two parallel independent span structures was chosen. The program of aerodynamic test at the wind-tunnel was given at the paper. The paper presents the test results for the most interesting angles of attack from the aerodynamic point of view. Based on the test results, it was established that it is impossible to speak unequivocally about the effect of snow deposits on the aerodynamic stability of the span. The presence of automobile traffic on the span under study excludes all possible phenomena of aerodynamic instability, for all the flow directions considered.

Modeling Blowing Snow Over the Tibetan Plateau With the Community Land Model: Method and Preliminary Evaluation

AbstractSnow cover in mountainous terrain plays an important role in regional and global water and energy balances, climate change, and ecosystems. Blowing snow is a frequent and important weather phenomenon over the Tibetan Plateau (TP); however, this process is neglected in most current land surface models, despite the consequential role it plays in the land surface and atmospheric water and energy budgets. In this paper, we present a blowing snow model PIEKTUK coupled with the Community Land Model (CLM4.5) to provide a better estimate of the snow dynamics for the consideration of snow redistribution induced by wind. Two simulations with a 0.065° spatial resolution were performed in 2010 over the TP, namely, a sensitivity experiment with the inclusion of blowing snow effects (CLM_BS) and a control run with the original model (CLM). A specific objective of this study was to evaluate the improvements in the simulations of snow dynamics and other key variables in surface energy partitioning provided by the coupled model, such as the surface albedo and land surface temperature (LST). Compared with a variety of remote‐sensing observations, the results show that the surface snow cover, snow depth, and surface albedo can be better reproduced in most of the TP region by CLM_BS than by the original CLM, particularly in the Kunlun Mountains, Hoh Xil area, and the southwestern TP. In areas with reduced bias, variations in the monthly mean snow cover fraction can be reflected particularly well by CLM_BS. For LST, however, a significant decrease in the nighttime LST bias was detected in CLM_BS, while the bias in the daytime LST increases. The results show considerable potential for the inclusion of the blowing snow process to promote the modeling of snow dynamics and land‐atmosphere interactions on the TP.

Sea salt aerosol production via sublimating wind-blown saline snow particles over sea ice: parameterizations and relevant microphysical mechanisms

Abstract. Blowing snow over sea ice has been proposed as a significant source of sea salt aerosol (SSA) (Yang et al., 2008). In this study, using snow salinity data and blowing snow and aerosol particle measurements collected in the Weddell Sea sea ice zone (SIZ) during a winter cruise, we perform a comprehensive model–data comparison with the aim of validating proposed parameterizations. Additionally, we investigate possible physical mechanisms involved in SSA production from blowing snow. A global chemical transport model, p-TOMCAT, is used to examine the model sensitivity to key parameters involved, namely blowing-snow size distribution, snow salinity, sublimation function, surface wind speed, relative humidity, air temperature and ratio of SSA formed per snow particle. As proposed in the parameterizations of Yang et al. (2008), the SSA mass flux is proportional to the bulk sublimation flux of blowing snow and snow salinity. To convert the bulk sublimation flux to SSA size distribution requires (1) sublimation function for snow particles, (2) blowing-snow size distribution, (3) snow salinity and (4) ratio of SSA formed per snow particle. The optimum model–cruise aerosol data agreement (in diameter range of 0.4–12 µm) indicates two possible microphysical processes that could be associated with SSA production from blowing snow. The first one assumes that one SSA is formed per snow particle after sublimation, and snow particle sublimation is controlled by the curvature effect or the so-called “air ventilation” effect. The second mechanism allows multiple SSAs to form per snow particle and assumes snow particle sublimation is controlled by the moisture gradient between the surface of the particle and the ambient air (moisture diffusion effect). With this latter mechanism the model reproduces the observations assuming that one snow particle produces ∼10 SSA during the sublimation process. Although both mechanisms generate very consistent results with respect to observed aerosol number densities, they correspond to completely different microphysical processes and show quite different SSA size spectra, mainly in ultra-fine and coarse size modes. However, due to the lack of relevant data, we could not, so far, conclude confidently which one is more realistic, highlighting the necessity of further investigation.

Does social learning promote cooperation in social dilemmas?

In this study, we analyze how emergence of cooperation is related to social learning. Cooperation is an example of social behavior. It is frequency-dependent that is the success of a particular behavior depends on the number of individuals adopting each behavioral trait. We study how social learning can affect the evolution of cooperation in social dilemmas represented by two well-known games: Prisoner’s Dilemma (PD) and Snowdrift (SD). We show that, in the PD game, increase in the proportion of social learners leads to the alleviation of the social dilemma. Whereas, in the SD game increasing the proportion of social learners does not always lead to the alleviation of the social dilemma, that is there is no simple monotonic relation between social learning and the weakening of the social dilemma.

Blowing Snow Transport Analysis for Estimating Drift Orientation and Severity

AbstractA methodology for performing a snow drift transport analysis is provided that considers the demonstrated dependency of snow transport on approximately the fourth power of wind speed, giving...

A study of snow drifting on a flat roof during snowfall based on simulations in a cryogenic wind tunnel

Wind tunnel simulation is a very important approach to studying snow drifting and predicting drift snow loads on roofs. A complete simulation of the full process of wind-induced snow accumulation on a roof should include snow drifting both during snowfall and after snowfall. However, in most of the previous studies, snow drifting phenomenon was only simulated without concurrence of snowfall. We herein describe simulations of snow drifting on a flat roof during snowfall, which were carried out in a cryogenic wind tunnel using artificial snow particles. Based on the results, we demonstrate the differences and similarities between snow drifting during snowfall and that without concurrent snowfall. The developments of snow transport before saturated state apparently follow the same rule, no matter whether there is concurrent snowfall or not. However, it seems that the required fetch distance for a saturated saltation state can be reduced by snowfall. A formula is proposed to more reasonably describe the development of snow transport rate. Based on test results and deductions, some discussions on similarity requirements for modelling snow drifting on roofs during snowfall will be presented. Finally, a prediction of the prototype fetch distances under different wind and snowfall conditions will also be presented, which can provide a guide for further research and engineering application.

Assessment of snow drift impact in the northern steppe region of China

The process of blowing snow is important for secondary distribution of water resources in seasonal grassland snow areas because it affects the regeneration, growth, and nutrient circulation of vegetation. This study conducted field observations of blowing snow and snow accumulation in a grassland area typical of northern China. The results showed that in the near-surface area (0 to 100 cm), snow drifting intensity increased exponentially with a mean wind speed of 2 m/s, and that the maximum snow drifting intensity, which was found within 30 cm of the surface, accounted for 89.61% of the total amount of snow drifting within the near-surface area. The snow drifting intensity was strong under conditions of an abundant snow source and sparse vegetation, with an average value of 2.203 g/cm/min. The snow drifting intensity was lower under conditions of an insufficient snow source and higher vegetation coverage, with an average value of 0.545 g/cm/min. In typical grassland areas with a bare surface and sparse vegetation, snow cover is generally thin; the mean snow depth in such areas during the observation period of this study was 4.03 cm, and this constituted the source of the drifting snow. Snow cover was thicker in areas with taller grass and greater vegetation coverage; the mean value of snow depth in such areas during the observation period was 16.56 cm, and this constituted the main snow cover area. The observation results provide basic data to support the estimation of snow cover amount in grassland ecosystems, optimization of the utilization of snow water resources, regularization of snow cover, restoration of vegetation, and prevention and control of snowstorms.

Improved Snow Drift Relations

AbstractDrift loads on roofs are arguably the most important snow load from a structural engineering perspective in the US, as they are the governing load for most cases of snow related structural ...

Implications of stubble management on snow hydrology and meltwater partitioning

Spring snowmelt is the most important hydrological event in agricultural cold regions, recharging soil moisture and generating the majority of annual runoff. Melting agricultural snowcovers are patchy, which leads to melt rate enhancement by energy advection from warm moist snow-free surfaces to cool dry snowcovers. Agricultural snowmelt is also impacted by crop residue. Adoption of zero-tillage agricultural practices means vast areas of the Canadian Prairies are now characterized by standing crop stubble. Stubble influences snow accumulation through blowing snow processes and snowmelt through the impact of emerging stubble upon the surface energy balance. Unfortunately, stubble emergence and advection to patchy snowcovers are unaccounted for in snow hydrology models and a complete process description has been unavailable. Here, both advection and stubble influences on snowmelt hydrology are modelled by coupling new stubble-snow-atmosphere surface energy balance and advection models to existing blowing snow and frozen soil infiltration models. Long-term meteorological datasets from sub-humid and semi-arid locations in Saskatchewan, Canada are used to quantify the influence of stubble characteristics on accumulation, melt, and meltwater partitioning processes with respect to interannual variability, antecedent soil moisture, and climatic differences on the Canadian Prairies. The hydrological response to increasing stubble height is increased meltwater, melt rate, infiltration, and runoff, and negligible changes in melt duration. The response of these processes to changes in stubble height was more pronounced at a semi-arid site versus a sub-humid site as stubble more effectively suppresses blowing snow sublimation in the windier, drier semi-arid environment of southwestern Saskatchewan. Recommendations for stubble management to meet specific runoff or infiltration objectives are summarised; stubble management can be an effective tool to influence infiltration where soils are dry and runoff where soils are wet. This framework allows the diagnosis of the influence of stubble management on meltwater partitioning in cold agricultural regions.

Accessing genetic variation using arbitrary oligonucleotide markers system in apple genotypes

A core collection of 50 apple genotypes was taken into consideration to access the genetic diversity and phylogenetic relationship using arbitrary oligonucleotide RAPD and ISSR markers system. The level of polymorphism across the subjected genotypes was 67.26% and 64.56% by RAPD and ISSR markers, respectively. Dendrogram grouped the subjected apple genotypes among three major clusters with similarity coefficient ranging from 0.20 to 0.94 using RAPD and among four major clusters with similarity coefficient ranging from genotypes. The genotypes ‘Royal Delicious’ and ‘Snow Drift’ were found to be most distantly related to each other as revealed from pooled dendrogram analysis of both the markers. Estimates of pooled similarity coefficient ranging from 0.35 to 0.94 indicated a broad genetic base promising for application to future molecular screening, map construction, mining of desirable genes for genetic improvement of fruiting cultivars and comparative genomic studies, etc. Therefore, the obtained results in the present study confirmed the potential of subjected markers as a reliable, rapid and inexpensive discrimination method that could be helpful in framing more extensive studies on the determined apple genotypes.