Winter Snow Accumulation Research Articles

Seasonal Modulation of Crustal Seismicity in Northeastern Japan Driven by Snow Load

AbstractNumerous studies have reported that surface hydrological loading can seasonally modulate seismicity rates at crustal depths. For example, substantial winter snow accumulation occurs across the Japanese Islands, and these snowy regions appear to have seasonally modulated the occurrence of previous large inland earthquakes. Therefore, it is important to investigate the impact of seasonal stress changes on crustal seismicity to deepen our understanding of earthquake generation. Here we constrain seasonal changes in the surface load across northeastern Japan using Global Navigation Satellite System surface displacements and evaluate the potential relationship between temporal trends in inland seismicity and estimated seasonal stress changes. The spatial distribution of the seasonal surface load is consistent with snow depth along the Sea of Japan. The inland seismicity beneath northeastern Japan is modestly modulated by the seasonal stress changes that are induced by the annual snow load. However, this seasonal response is weaker than that in other regions. This weak modulation may be due to the small surface‐load‐induced stress perturbation relative to the long‐term‐averaged stressing rate and/or the limited presence of crustal fluids to trigger seismicity in Japan.

Recent Mass Balance Anomalies on the Djankuat Glacier, Northern Caucasus

A 54-year-long series of continuous instrumental measurements of mass balance and its main components has already been accumulated at the Djankuat Glacier, which is representative of the Caucasus and the most studied glacier in Russia. The anomalies of these indicators in 2017/2018–2020/2021 were evaluated against an analysis of meteorological reasons that predetermined them. Each of the four balance years under consideration represents a particular anomaly of varying severity. As for conditions of mass income, three years saw accumulation higher than average, and in one year (2018/2019) it approached the norm. As for summer ablation conditions, similarly, in one season (2019) the melting differed from the average only slightly, but in the other three it was much higher. Consequently, in one year (2020/2021) the state of the glacier was close to normal, in another (2017/2018) the budget situation was much more favorable for Djankuat, and in the other two the final losses significantly exceeded the average annual mass loss rate. At the same time, in 2019/2020, an absolute record of ablation since the beginning of monitoring in 1967/1968 was recorded (4360 mm w.e.). Nevertheless, although negative mass balance values continue to be recorded annually, signs of an inevitable slowdown in the rate of glacier degradation in the Caucasus have appeared in the last 4-year-long period: the continued growth of winter snow accumulation overlaps the ongoing intensification of summer melting. The growth of debris cover in terms of area and thickness also affects this mass loss slowdown to some extent. This inhibits ablation, exerting a heat-insulating effect. Because of this, the congruence of mass balance parameters vs. altitude curves is distorted. Also, a tendency toward increasing annual glacier mass turnover was revealed for the last half-century. This fact gradually increases the energy of glaciation and indirectly indicates a weakening of continentality in the climate of the Caucasian highlands.

Towards robust seasonal streamflow forecasts in mountainous catchments: impact of calibration metric selection in hydrological modeling

Abstract. Dynamical (i.e., model-based) methods are widely used by forecasting centers to generate seasonal streamflow forecasts, building upon process-based hydrological models that require parameter specification (i.e., calibration). Here, we investigate the extent to which the choice of calibration objective function affects the quality of seasonal (spring–summer) streamflow hindcasts produced with the traditional ensemble streamflow prediction (ESP) method and explore connections between hindcast skill and hydrological consistency – measured in terms of biases in hydrological signatures – obtained from the model parameter sets. To this end, we calibrate three popular conceptual rainfall-runoff models (GR4J, TUW, and Sacramento) using 12 different objective functions, including seasonal metrics that emphasize errors during the snowmelt period, and produce hindcasts for five initialization times over a 33-year period (April 1987–March 2020) in 22 mountain catchments that span diverse hydroclimatic conditions along the semiarid Andes Cordillera (28–37∘ S). The results show that the choice of calibration metric becomes relevant as the winter (snow accumulation) season begins (i.e., 1 July), enhancing inter-basin differences in hindcast skill as initializations approach the beginning of the snowmelt season (i.e., 1 September). The comparison of seasonal hindcasts shows that the hydrological consistency – quantified here through biases in streamflow signatures – obtained with some calibration metrics (e.g., Split KGE (Kling–Gupta efficiency), which gives equal weight to each water year in the calibration time series) does not ensure satisfactory seasonal ESP forecasts and that the metrics that provide skillful ESP forecasts (e.g., VE-Sep, which quantifies seasonal volume errors) do not necessarily yield hydrologically consistent model simulations. Among the options explored here, an objective function that combines the Kling–Gupta efficiency (KGE) and the Nash–Sutcliffe efficiency (NSE) with flows in log space provides the best compromise between hydrologically consistent simulations and hindcast performance. Finally, the choice of calibration metric generally affects the magnitude, rather than the sign, of correlations between hindcast quality attributes and catchment descriptors, the baseflow index and interannual runoff variability being the best predictors of forecast skill. Overall, this study highlights the need for careful parameter estimation strategies in the forecasting production chain to generate skillful forecasts from hydrologically consistent simulations and draw robust conclusions on streamflow predictability.

Atmospheric Circulation Anomalies and Key Physical Processes behind Two Categories of Anomalous Eurasian Spring Snowmelt

Abstract Eurasian spring snowmelt plays an important role in the subsequent climate and hydrological cycle, however, the understanding of snowmelt itself and its causes remains insufficient. This study explored the basic characteristics of spring snowmelt in the eastern Europe–western Siberia (EEWS) region by classifying snowmelt anomalies into two categories based on the different factors that dominate spring snowmelt, and then investigated the associated atmospheric circulation anomalies and local physical processes. The first category of anomalous snowmelt (category 1) is controlled by both the initial snow mass and the later snowmelt process, while the second category of anomalous snowmelt (category 2) is mainly linked to the later snowmelt process. Specifically, category 1 is characterized by an anomalous trough in EEWS in winter, where water vapor transported and converged, accompanied by anomalous upward motion, which promotes snowfall and snow accumulation, providing initial conditions conducive to snowmelt. In April, this region is controlled by an anomalous ridge, with significant warm advection anomalies and subsidence promoting surface warming, thereby accelerating snow melting. In contrast, the winter circulation anomalies are insignificant in category 2, while the anomalous ridge in April is stronger than in category 1, accompanied by more intense snowmelt processes. In addition, from the surface energy balance perspective, atmospheric downward sensible heat transport is an important factor influencing the anomalous snowmelt in category 1, while shortwave radiation plays a secondary role. Conversely, the snowmelt in category 2 is dominated by shortwave radiation forcing, but the sensible heat effect is slightly weaker. Significance Statement Eurasian spring snowmelt significantly impacts the subsequent climate and hydrological cycle, but the understanding of snowmelt itself and its causes is still inadequate. The purpose of this study is to explore the monthly evolution of atmospheric circulation associated with anomalous snowmelt and its local physical processes associated by categorizing them based on snowmelt characteristics. Category 1 is jointly affected by winter snow accumulation and later warming, while category 2 is dominated by strong snowmelt process in late spring. These two categories are accompanied by different winter and spring circulation configurations. Our results provide a basis for further investigation of snowmelt precursor signals.

The Increasing Role of Seasonal Rainfall in Western U.S. Summer Streamflow

AbstractSummer streamflow variations strongly affect water supply reliability and ecological functioning of western U.S. (WUS) streams. Traditional snow‐based forecasts of summer streamflow are becoming less accurate with warming‐induced reductions in winter snow accumulation. This reflects a rising importance of competing runoff‐generating processes in controlling summer streamflow variations, primarily an increasing role of rainfall in contrast to snowmelt. Here, based on a snowmelt‐rainfall tracking algorithm applied to two hydrological models, we show that cool‐season rainfall provides an important volumetric contribution to summer streamflow for many WUS streams in the current climate, and this contribution will increase under climate warming, especially in years with warm snow droughts and abnormally dry summers. We also show that seasonal rainfall (warm‐/cool‐seasons) dominates the variability of summer streamflow across ∼70% area of WUS. We show that an increasing warm‐season rainfall contribution to summer streamflow (largely replacing snowmelt) results in reduced summer streamflow predictability.

Snow drought and monsoon floods—hydrological extremes in the Cedar Valley watershed during water year 2021, southwestern Utah

Water year 2021 was a year of extremes in the Cedar Valley watershed of southern Utah, with snow drought resulting in extremely low snowmelt runoff of Coal Creek and intense monsoon rainfall resulting in several floods in different parts of the valley. Winter snow accumulation was depressed throughout southern Utah, perhaps due to La Nina conditions affecting winter storm trajectories. Coal Creek, the principal stream providing surface water to Cedar Valley, typically receives most of its annual flow from snowmelt runoff, but in 2021 had a peak snowmelt discharge 15% to 25% of that recorded in the previous two years and the third lowest snowmelt runoff on record. Following this extremely low snowmelt runoff period, more than 10 floods of Coal Creek occurred following monsoon storms in July and August that exceeded the 2021 snowmelt peak. Additionally, several thunderstorms produced rainfall rates in exceedance of the 100-year event and induced flooding within Cedar City and the town of Enoch. Flood inundation modeling using HEC-RAS and high-resolution topographic data showed good agreement with field and pubic-survey data on the high-water stage during the Enoch flooding, and demonstrated that the flooding was likely exacerbated by the low topography and limited drainage potential in flooded areas. Whereas the monsoon storms improved soil moisture and helped alleviate drought conditions, they also resulted in urban flooding and did little to replenish the regional water supply.

Expansion of Firn Aquifers in Southeast Greenland

AbstractSurface melt produces more mass loss than any other process on the Greenland Ice Sheet. In some regions of Greenland with high summer surface melt and high winter snow accumulation, the warm porous firn of the percolation zone can retain liquid meltwater through the winter. These regions of water‐saturated firn, which may persist for longer than one year, are known as firn aquifers, commonly referred to as perennial firn aquifers. Here, we use airborne ice‐penetrating radar data from the Center for Remote Sensing of Ice Sheets (CReSIS) to document the extent of four firn aquifers in the Helheim, Ikertivaq, and Køge Bugt glacier basins with more than six repeat radar flight lines from 1993 to 2018. All four firn aquifers first appear and/or show decadal‐scale inland expansion during this time period. Through an idealized energy‐balance calculation utilizing reanalysis data from the Modèle Atmosphérique Régionale (MAR) regional climate model, we find that these aquifer expansions are driven by decreasing cold content in the firn since the late 1990s and recently increasing high‐melt years, which has reduced the firn's ability for refreezing local meltwater. High‐melt years are projected to increase on the Greenland Ice Sheet and may contribute to the continued inland expansion of firn aquifers, impacting the ice sheet's surface mass balance and hydrological controls on ice dynamics.

Contrasting Fate of Western Third Pole's Water Resources Under 21st Century Climate Change

AbstractSeasonal melting of glaciers and snow from the western Third Pole (TP) plays important role in sustaining water supplies downstream. However, the future water availability of the region, and even today's runoff regime, are both hotly debated and inadequately quantified. Here, we characterize the contemporary flow regimes and systematically assess the future evolution of total water availability, seasonal shifts, and dry and wet discharge extremes in four most meltwater‐dominated basins in the western TP, by using a process‐based, well‐established glacier‐hydrology model, well‐constrained historical reference climate data, and the ensemble of 22 global climate models with an advanced statistical downscaling and bias correction technique. We show that these basins face sharply diverging water futures under 21st century climate change. In RCP scenarios 4.5 and 8.5, increased precipitation and glacier runoff in the Upper Indus and Yarkant basins more than compensate for decreased winter snow accumulation, boosting annual and summer water availability through the end of the century. In contrast, the Amu and Syr Darya basins will become more reliant on rainfall runoff as glacier ice and seasonal snow decline. Syr Darya summer river‐flows, already low, will fall by 16%–30% by end‐of‐century, and striking increases in peak flood discharge (by >60%), drought duration (by >1 month) and drought intensity (by factor 4.6) will compound the considerable water‐sharing challenges on this major transboundary river.

Geophysical research on the IGAN Glacier in 2021

The results of radar studies of the IGAN glacier carried out in 2019 and 2021 are presented in the paper. Measurements of the thickness of the snow cover and ice were carried out using the PICOR-LED GPR (1600 MHz) and VIRL-7 (20 MHz), respectively. Studies have revealed significant winter snow accumulation on the glacier and its stable spatial distribution, and also showed a significant ice thickness (up to 106 m) and the polythermal structure of the glacier. Electrotomography was used to monitor the central part of the glacial moraine. Two-dimensional geoelectric sections and a three-dimensional geoelectric model of the internal structure of the moraine are constructed. The size of the rock-ice core (high-resistance rocks) increases towards the center of the moraine, nevertheless, there is an active degradation of frozen material in the marginal parts of the moraine.

Long-term effects of snowmelt timing and climate warming on phenology, growth, and reproductive effort of Arctic tundra plant species

Arctic regions are particularly affected by rapidly rising temperatures and altered snow regimes. Snowmelt timing depends on spring temperatures and winter snow accumulation. Scenarios for the Arctic include both decreases and increases in snow accumulation. Predictions of future snowmelt timing are, thus, difficult and experimental evidence for ecological consequences is scarce. In 1995, a long-term factorial experiment was set up in a High Arctic evergreen shrub heath community on Ellesmere Island, Canada. We investigated how snow removal, snow addition, and passive warming affected phenology, growth and reproductive effort of the four common tundra plant species Cassiope tetragona (L.) D. Don, Dryas integrifolia Vahl, Luzula arctica Blytt, and Papaver radicatum Rottb. Timing of flowering and seed maturation as well as flower production were more strongly influenced by the combined effects of snowmelt timing and warming in the two shrub species than in the two herbaceous species. Warming effects persisted over the course of the growing season and resulted in increased shrub growth. Moreover, the long-term trend of increasing growth in two species suggests that ambient warming promotes tundra plant growth. Our results confirm the importance of complex interactions between temperature and snowmelt timing in driving species-specific plant responses to climate change in the Arctic.

Factors Governing Winter Snow Accumulation and Ablation Susceptibility Across the Sierra Nevada, U.S.A.

AbstractSeasonal snow water equivalent (SWE) accumulation in California’s Sierra Nevada is primarily governed by a few orographically enhanced snowstorms. However, as air temperatures gradually rise, resulting in a shift from snow to rain, the governing processes determining SWE accumulation versus ablation become ambiguous. Using a network of 28 snow pillow measurements to represent an elevational and latitudinal gradient across the Sierra Nevada, we identify distributions of critical temperatures and corresponding storm and snowpack properties that describe how SWE accumulation varies across the range at an hourly timescale for water years 2010 through 2019. We also describe antecedent and prevailing conditions governing whether SWE accumulates or ablates during warm storms. Results show that atmospheric moisture regulates a temperature dependence of SWE accumulation. Conditions balancing precipitable water and snow formation requirements produce the most seasonal SWE, which was observed in the (low-elevation) northern and (middle-elevation) central Sierra Nevada. The high southern Sierra Nevada conservatively accumulates SWE with colder, drier air, resulting in less midwinter ablation. These differences explain a tendency for deep, low-density snowpacks to accumulate rather than ablate SWE during warm storms (having median temperatures exceeding 1.0°C), reflecting counteracting liquid storage and internal energy deficits. The storm events themselves in these cases are brief with modest moisture supplies or are otherwise followed immediately by ablation.

Seasonal Precipitation and Soil Moisture Relationships Across Forests and Woodlands in the Southwestern United States

AbstractPrecipitation [P: mm] controls forest and woodland dynamics in the southwestern United States (SWUS) by altering soil moisture [θ: mm3 mm−3] availability, but the influence of P on θ is complex, varying across space and time. We evaluated seasonal P and θ relationships at shallow (0–20 cm) and intermediate (50 cm) soil depths for nine semiarid forest and woodland sites (56 total years), which comprised three elevation gradients in the SWUS. We developed time‐varying definitions of winter (snow accumulation), spring (moisture recharge), and summer (moisture deficit), and determined how these sites exhibited similar P influence on θ across depths in the soil profile, between seasons, and in seasons with above‐ and below‐average P. Higher elevation sites (>2,800 m) experienced greater winter P, longer springs, and shorter summers compared to lower elevation sites (<2,500 m). Seasons with above‐ and below‐average P reduced elevation‐associated differences. θ at 0–20 cm was generally decoupled from θ at 50 cm in seasons with average and below‐average P, imparted by differences in spring and summer rainfall versus winter snowfall. Notably, across‐season influence of θ (e.g., a season’s similarity to subsequent seasons) was high when the first season experienced above‐ or below‐average P, and the subsequent season experienced average P, illustrating an important temporal connection initiated by wet and dry conditions. These results illustrate similarities in P‐θ relationships across widely differing ecosystems in the SWUS, and elucidate how these relationships may be altered in a changing climate.

Response of U.S. West Coast Mountain Snowpack to Local Sea Surface Temperature Perturbations: Insights from Numerical Modeling and Machine Learning

AbstractSea surface temperature (SST) significantly modulates the precipitation and temperature over land, with important consequences on land surface processes such as snowpack. Compared to the impact of remote SST, the effect of nearshore/local SST is less well understood. In this study, the impact of local SST on the mountain snowpack of the U.S. West Coast is investigated using two 6-km regional climate simulations driven by the same lateral boundary conditions but with time-varying versus time-invariant and warmer local SSTs during 2003–15. Results show that local SST warming leads to warmer winter with more precipitation over the mountains. Meanwhile, the removal of SST temporal variability results in reduced temperature variability but increased precipitation variability. As a result, winter snow accumulation decreases by ~200 mm per season in the Cascade Mountains in the north but increases by ~100 mm per season in the Sierra Nevada in the south. Such a dipole response results from the competing effects of precipitation and temperature change at different elevations and are amplified by the enhanced atmospheric river moisture transport. To further delineate the relative contributions of different meteorological factors to the snowpack response, two neural network models were developed to predict the snow behaviors at seasonal and monthly scales. These models reveal the dominant influence of the total amount and the average temperature of precipitation on the snowpack response. These findings highlight the sensitivity of mountain snowpack to local SST in the western United States and underscore the importance of local SST and atmospheric rives to accurate snowpack estimations for water management.

Flowering Phenology Adjustment and Flower Longevity in a South American Alpine Species.

Delayed flowering due to later snowmelt and colder temperatures at higher elevations in the alpine are expected to lead to flowering phenological adjustment to prevent decoupling of peak flowering from the warmest time of the year, thereby favoring pollination. However, even if flowering is brought forward in the season at higher elevations, an elevational temperature gap is likely to remain between the high- and low-elevation populations of a species at the time these reach peak flowering on account of the atmospheric reduction in temperature with increasing elevation. The negative effect of this temperature gap on pollination could be compensated by plastically-prolonged flower life spans at higher elevations, increasing the probability of pollination. In a tightly temperature-controlled study, the flowering phenology adjustment and flower longevity compensation hypotheses were investigated in an alpine species in the Andes of central Chile. The snow free period varied from 7 to 8.2 months over 810 m elevation. Temperatures were suitable for growth on 82–98% of the snow free days. Flowering onset was temporally displaced at the rate of 4.6 d per 100 m increase in elevation and flowering was more synchronous at higher elevations. Flowering phenology was adjusted over elevation. The latter was manifest in thermal sums tending to decrease with elevation for population flowering onset, 50% flowering, and peak flowering when the lower thermal limit for growth (TBASE) was held constant over elevation. For TBASE graded over elevation so as to reflect the growing season temperature decline, thermal sums did not vary with elevation, opening the door to a possible elevational decline in the thermal temperature threshold for growth. Potential flower longevity was reduced by passive warming and was more prolonged in natural populations when temperatures were lower, indicating a plastic trait. Pollination rates, as evaluated with the Relative Pollination Rate index (RPR), when weighted for differences in floral abundance over the flowering season, declined with elevation as did fruit set. Contrary to expectation, the life-spans of flowers at higher elevations were not more prolonged and failed to compensate for the elevational decrease in pollination rates. Although strong evidence for phenological adjustment was forthcoming, flower longevity compensation did not occur over Oxalis squamata’s elevational range. Thus, flower longevity compensation is not applicable in all alpine species. Comparison with work conducted several decades ago on the same species in the same area provides valuable clues regarding the effects of climate change on flowering phenology and fitness in the central Chilean alpine where temperatures have been increasing and winter snow accumulation has been declining.

Recent Increases in Winter Snowfall Provide Resilience to Very Small Glaciers in the Julian Alps, Europe

Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. This study seeks to better understand the impact of extreme snowfall events on the resilience of very small glaciers and ice patches in the southeastern European Alps, an area with the highest mean annual precipitation in the entire Alpine chain. Mean annual precipitation here is up to 3300 mm water equivalent, and the winter snow accumulation is approximately 6.80 m at 1800 m asl averaged over the period 1979–2018. As a consequence, very small glaciers and ice/firn patches are still present in this area at rather low altitudes (1830–2340 m). We performed repeated geodetic mass balance measurements on 14 ice bodies during the period 2006–2018 and the results show an increase greater than 10% increase in ice volume over this period. This is in accordance with several extreme winter snow accumulations in the 2000s, promoting a positive mass balance in the following years. The long-term evolution of these very small glaciers and ice bodies matches well with changes in mean temperature of the ablation season linked to variability of Atlantic Multidecadal Oscillation. Nevertheless, the recent behaviour of such residual ice masses in this area where orographic precipitation represents an important component of weather amplification is somehow different to most of the Alps. We analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the influence and modification of atmospheric planetary waves and Arctic Amplification, with further positive feedbacks due to change in local sea surface temperature and its interactions with low level flows and the orography. Although further summer warming is expected in the next decades, we conclude that modification of storm tracks and more frequent occurrence of extreme snowfall events during winter are crucial in ensuring the resilience of small glacial remnants in maritime alpine sectors.

Too hot for our own good

Ice Sheets Climate is warming faster in the Arctic than in any other large region, and the Greenland Ice Sheet is melting faster as a result. Noel et al. project that the rate of summertime surface melting will surpass that of winter snow accumulation in Greenland when the average air temperature there rises to 4.5°C above preindustrial values, which corresponds to a global warming threshold of 2.7°C. Without strong CO2 emission mitigation measures, net surface mass loss could occur as soon as the middle of the 21st century. Geophys. Res. Lett. 10.1029/2020GL090471 (2021).

Inter-comparison of snow depth over Arctic sea ice from reanalysis reconstructions and satellite retrieval

Abstract. In this study, we compare eight recently developed snow depth products over Arctic sea ice, which use satellite observations, modeling, or a combination of satellite and modeling approaches. These products are further compared against various ground-truth observations, including those from ice mass balance observations and airborne measurements. Large mean snow depth discrepancies are observed over the Atlantic and Canadian Arctic sectors. The differences between climatology and the snow products early in winter could be in part a result of the delaying in Arctic ice formation that reduces early snow accumulation, leading to shallower snowpacks at the start of the freeze-up season. These differences persist through spring despite overall more winter snow accumulation in the reanalysis-based products than in the climatologies. Among the products evaluated, the University of Washington (UW) snow depth product produces the deepest spring (March–April) snowpacks, while the snow product from the Danish Meteorological Institute (DMI) provides the shallowest spring snow depths. Most snow products show significant correlation with snow depths retrieved from Operational IceBridge (OIB) while correlations are quite low against buoy measurements, with no correlation and very low variability from University of Bremen and DMI products. Inconsistencies in reconstructed snow depth among the products, as well as differences between these products and in situ and airborne observations, can be partially attributed to differences in effective footprint and spatial–temporal coverage, as well as insufficient observations for validation/bias adjustments. Our results highlight the need for more targeted Arctic surveys over different spatial and temporal scales to allow for a more systematic comparison and fusion of airborne, in situ and remote sensing observations.

ОПЫТ ПРИМЕНЕНИЯ ВЫСОКОЧАСТОТНОГО ГЕОРАДАРА ДЛЯ ЛАНДШАФТНОЙ СНЕГОМЕРНОЙ СЪЁМКИ В ОКРЕСТНОСТЯХ ГОРОДОВ КИРОВСК (ХИБИНЫ) И АПАТИТЫ

The results of processing of a profile snow-measuring survey of snow cover in the Khibiny Mountains are presented. The survey was performed during the period of maximum snow accumulation (March of 2020) on the main elements of the landscape: mixed forest on the plain, open woodlands at the bottom of valleys, plateaus, wooded slopes, and upper slopes without woody vegetation. The averaged values of snow storage for different types of the landscapes were obtained for the period of the maximum snow accumulation in the snowy winter of 2019/20. The maximum snow storage (> 700 mm w.e.) was determined for areas on the high plateaus and open woodlands at the bottom of valleys. Minimum snow storage (> 400 mm w.e.) was recorded in areas of mixed forest on the plain and on an ice cover of lakes. Measurements of snow depth were carried out by the standard method (a handspike) and the ground-based radio-echo sounding using georadar with the frequency of 1600 MHz. The accuracy of this method allows measuring of the snow depth with accuracy of 1 cm for a dense snow and 2 cm for a loose one. Thus, the accuracy of measuring the snow depth with the radar is comparable to the accuracy of a handspike. A large number of radar measurements of snow depth on the profiles makes possible to determine the spatial variability of this value and its statistical characteristics. As a result, a vertical gradient of snow accumulation was defined as 25 mm w.e. per 100 m. The smallest spatial variability of snow depth was observed on profiles in the forests on the plain, in woodlands, and on the upper slopes. On profiles with complex relief (plateau, lower slopes), the spatial variability of snow depth is significant – the standard deviation was within limits of 30%. Based on the results of processing the field data, a map of snow storage over the studying area during the period of maximum snow accumulation was constructed. When constructing the map, we took into account the averaged data of the measurements for each type of landscape, the boundaries of woody vegetation, the height, steepness of slopes, and the high-altitude gradient of snow accumulation. It was found that features of the spatial distribution of snow cover were primarily due to the location of natural landscape complexes. The role of changes in snow storages with altitude was found to be insignificant.

Snow removal method for self-heating of photovoltaic panels and its feasibility study

To solve the problem of winter snow accumulation in photovoltaic power stations, a new method of self-heating to remove snow from photovoltaic panels is proposed. This method overcomes the drawbacks of existing methods. No additional devices are needed, and photovoltaic cell wear, resource waste, and safety risk is reduced. Using the structural characteristics of the pn junction in the photovoltaic cell, a positive voltage is applied to the photovoltaic panel to melt the snow layer on the surface of the photovoltaic panel, and then the snow layer slides down from the photovoltaic panel by gravity. The heat transfer model and the mechanical model of photovoltaic panel snow removal were established. The minimum inclination angle of photovoltaic panel was calculated by the mechanical model. The corresponding experimental research was carried out. The front surface temperature of the photovoltaic panel was simulated by Matlab software, and compared with the experimental results to verify the transfer model. It is concluded that the method of self-heating to remove snow on the photovoltaic panel was feasible when the thickness of the snow was greater than the equivalent height and the inclination angle of the photovoltaic panel was greater than the minimum inclination angle. And the increase in snow thickness is beneficial to the snow removal performance of this method. When the thickness of the snow increased by 1 cm, and the total snow removal duration was shortened by about 6 min.

Glaciers and climate of the Upper Susitna basin, Alaska

Abstract. Extensive field observations were conducted in the Upper Susitna basin, a 13 289 km2 glacierized catchment in central Alaska in 2012–2014. This paper describes the comprehensive data set of meteorological, glacier mass balance, snow cover, and soil measurements, as well as the data collection and processing. Results are compared to similar observations from the 1980s. Environmental lapse rates measured with weather stations between about 1000 and 2000 m a.s.l. were significantly lower over the glaciers than the non-glacierized areas. Glacier-wide mass balances shifted from close to balanced in 1981–1983 to less than −1.5 m w.e. yr−1 in 2012–2014. Winter snow accumulation measured with ablation stakes on the glaciers closely matched observations from helicopter-borne radar. Soil temperature measurements across the basin showed that there was no permafrost in the upper 1 m of the soil column. The data produced by this study are available at: https://doi.org/10.14509/30138 (Bliss et al., 2019) and will be useful for hydrological and glaciological studies including modeling efforts.