Influence Of Snow Cover Research Articles

Analysis of the Effects of Different Snow Cover Mulches on Spatio-temporal Variationsof Farmland Soil Moisture

<abstract> <b><i>Abstract. </i></b> We investigated the influence of snow cover on soil moisture in a seasonally frozen area in northern China. To do this, we performed a field test during one freeze-thaw cycle with four treatments of the test area: bare land, normal snow cover, compacted snow cover, and thick snow cover. Soil moisture depth, liquid moisture depth, frost depth, temperature, solar radiation, and other meteorological data were measured to obtain a comprehensive analysis. One-way ANOVA with Duncan‘s multiple ranges test was used to evaluate significant differences between soil moisture among all four treatments. The results demonstrated that the different snow cover treatments led to significantly different levels of soil moisture. Soil moisture accumulation area appeared obvious temporal and spatial distribution differences. However, snow cover effectively inhibited large magnitude temporal and spatial variations of the soil liquid moisture content. The feedback adjustment capability of the total soil moisture content showed that shallow profiles were more affected by different snow cover treatments than deep profiles. The compacted snow treatment was most effective for conserving soil moisture in shallow soil and improving the liquid moisture content of deep soil.

Algorithms to estimate Antarctic sea ice algal biomass from under-ice irradiance spectra at regional scales

The presence of algal pigments in sea ice alters under-ice irradiance spectra, and the relationship between these variables can be used as a non-invasive means for estimating ice- associated algal biomass on ecologically relevant spatial and temporal scales. While the influence of snow cover and ice algal biomass on spectra transmitted through the snow-ice matrix has been examined for the Arctic, it has not been tested for Antarctic sea ice at regional scales. We used paired measurements of sea ice core chla concentrations and hyperspectral-transmitted under-ice irradiances from 59 sites sampled off East Antarctica and in the Weddell Sea to develop algorithms for estimating algal biomass in Antarctic pack ice. We compared 4 approaches that have been used in various bio-optical studies for marine systems: normalised difference indices, ratios of spectral irradiance, scaled band area and empirical orthogonal functions. The percentage of vari- ance explained by these models ranged from 38 to 79%, with the best-performing approach being normalised difference indices. Given the low concentrations of integrated chl a observed in our study compared with previous studies, our statistical models performed surprisingly well in explaining variability in these concentrations. Our findings provide a basis for future work to develop methods for non-invasive time series measurements and medium- to large-scale spatial mapping of Antarctic ice algal biomass using instrumented underwater vehicles.

Influence of snow cover on the thermal regime of a polythermal glacier in Western Spitsbergen

Influence of snow cover, climate and glacier parameters on the cold-ice layer thickness and thermal regime in the ablation area of a polythermal glacier in Western Svalbard was investigated. Numerical modeling has demonstrated that a thickness of a cold layer in a polythermal glacier depends on a relation between the ablation on the surface and the freezing rate at the layer base. If the ablation rate is lower than that of the freezing, the layer thickness grows until the ablation and freezing rates become equal. Estimations show that in a case of slightly negative air temperatures on the glacier its cold-ice layer thickness increases when the snow cover thickness grows.

The influence of surface characteristics, topography and continentality on mountain permafrost in British Columbia

Abstract. Thermal and surface offsets describe mean annual ground temperature relative to mean annual air temperature, and for permafrost modelling they are often predicted as a function of surface characteristics and topography. As macroclimatic conditions influence the effectiveness of the underlying processes, knowledge of surface- and topography-specific offsets is not easily transferable between regions, limiting the applicability of empirical permafrost distribution models over areas with strong macroclimatic gradients. In this paper we describe surface and thermal offsets derived from distributed measurements at seven field sites in British Columbia. Key findings are (i) a surprisingly small variation of the surface offsets between different surface types; (ii) small thermal offsets at all sites (excluding wetlands and peat); (iii) a clear influence of the micro-topography at wind exposed sites (snow-cover erosion); (iv) a north–south difference of the surface offset of 4 °C in vertical bedrock and of 1.5–3 °C on open (no canopy) gentle slopes; (v) only small macroclimatic differences possibly caused by the inverse influence of snow cover and annual air temperature amplitude. These findings suggest that topoclimatic factors strongly influence the mountain permafrost distribution in British Columbia.

On the influence of variability of snow cover parameters to the ground freezing

Depth and rate of the soil freezing are stronly determined by dynamics of snow accumulation during the first half of a cold season. Dynamics of snow accumulation over two periods (1966–2000 and 2001–2010) was analyzed using data of snow surveys performed on the European part of Russia and in basins of rivers Ob and Yenisei (Siberia). The ratio a of snow cover thickness measured for the first half of the cold season (untill January 1 st ) to the maximal thickness for the whole period is taken as a characteristic of the snow accumulation dynamics. Maps of the ratio a on the above areas had been constructed. During the last period (2001–2010) values of this ratio increased by 10–20% in regions to the East of the Lena river, and they decreased by 15–40% in the European part of Russia and in basins of rivers Ob and Yenisei. Model calculations did show that differences in the soil freezing depths under different conditions of the snow cover growth sometimes exceeded 50%. Interannual variability of the snow thermal resistance and the snow cover influence.

Observations and modeling of hillslope throughflow temperatures in a coastal forested catchment

AbstractA growing body of research on stream thermal regimes has highlighted the importance of heat advection associated with surface water and groundwater interactions, such as hyporheic exchange, groundwater discharge, and hillslope throughflow inputs. Existing catchment models that predict stream temperature use a variety of approaches to estimate throughflow temperatures, but none has been evaluated against field measurements of throughflow temperature. In this study, throughflow temperatures were monitored over two winters at 50 locations adjacent to a headwater stream (11 ha catchment area) located in the rain‐on‐snow zone of the Pacific Northwest. Existing approaches to estimate throughflow temperature under or overpredicted throughflow temperatures by up to 5°C, or were unable to represent the influence of transient snow cover. Therefore, a conceptual‐parametric model that is computationally efficient was developed that simulates hillslope hydrology and throughflow temperatures. The model structure includes an upslope reservoir that drains into a downslope reservoir that, in turn, drains into the stream. Vertical and lateral energy and water fluxes are simulated using simplified process representations. The model successfully predicts throughflow temperatures and highlights the dominant role of throughflow advection and the influence of snow cover on stream thermal regimes during high flow periods and rain‐on‐snow events.

Comparing springtime ice-algal chlorophyll a and physical properties of multi-year and first-year sea ice from the Lincoln Sea.

With near-complete replacement of Arctic multi-year ice (MYI) by first-year ice (FYI) predicted to occur within this century, it remains uncertain how the loss of MYI will impact the abundance and distribution of sea ice associated algae. In this study we compare the chlorophyll a (chl a) concentrations and physical properties of MYI and FYI from the Lincoln Sea during 3 spring seasons (2010-2012). Cores were analysed for texture, salinity, and chl a. We identified annual growth layers for 7 of 11 MYI cores and found no significant differences in chl a concentration between the bottom first-year-ice portions of MYI, upper old-ice portions of MYI, and FYI cores. Overall, the maximum chl a concentrations were observed at the bottom of young FYI. However, there were no significant differences in chl a concentrations between MYI and FYI. This suggests little or no change in algal biomass with a shift from MYI to FYI and that the spatial extent and regional variability of refrozen leads and younger FYI will likely be key factors governing future changes in Arctic sea ice algal biomass. Bottom-integrated chl a concentrations showed negative logistic relationships with snow depth and bulk (snow plus ice) integrated extinction coefficients; indicating a strong influence of snow cover in controlling bottom ice algal biomass. The maximum bottom MYI chl a concentration was observed in a hummock, representing the thickest ice with lowest snow depth of this study. Hence, in this and other studies MYI chl a biomass may be under-estimated due to an under-representation of thick MYI (e.g., hummocks), which typically have a relatively thin snowpack allowing for increased light transmission. Therefore, we suggest the on-going loss of MYI in the Arctic Ocean may have a larger impact on ice–associated production than generally assumed.

Influence of snow cover on soil freezing and thawing in the West Spitsbergen

This paper presents the results of experimental research of snow cover influence on ground freezing/thawing in Svalbard. Observations show that even before the snow disappearance ground thaws for dozens of centimeters that increases the thaw depth later in the season. Under the snow cover of 40 cm the thaw depth can reach 35–50 cm. The thawing can be caused by melt water with slightly positive temperature, percolating under the snow cover near the ground surface. The data on ground temperature regime during a year under various snow depths are given. Under a shallow snow cover the ground cools significantly, and this process causes the slowing down subsequent thawing.

Thermal resistance of snow cover and its effect on the ground freezing

Рассмотрена пространственно-временнaя изменчивость термического сопротивления снежного покрова для ряда районов Красноярского края и Якутии. Проведена корреляция глубины промерзания грунта с толщиной снежного покрова и его термическим сопротивлением. На основе математического моделирования дана оценка влияния параметров снежного покрова и грунта на глубину промерзания. Рассчитана критическая толщина снежного покрова, при превышении которой образуется несливающаяся мерзлота в сезонноталом грунте. Рассмотрены возможности и эффективность регулирования термического сопротивления снежного покрова для снижения отрицательных последствий потепления климата на деградацию многолетнемёрзлых грунтов.

To study the influence of snow cover on the power generated by photovoltaic modules

The possibility of increasing the power generation of PV modules due to radiation reflected from the snow is investigated. An experiment has been held to determine the value of the current generated by PV-modules on account of the underlying snow surface. Also the experiment has been held to determine the influence of the PV-module's location due the snow surface on the performance of solar cells.

Evaluating the Role of Snow Cover in Urban Canopy Layer on the Urban Heat Island in Sapporo, Japan with a Regional Climate Model

Climate monitoring in urban areas is important because climate change in densely populated areas has a strong influence on society. The rate of long-term temperature increase in high-latitude snowy urban areas is relatively large due to global warming and urban heat islands. However, the influence of snow cover on urban heat islands is unclear. The purpose of this study is to assess the effect of snow cover in urban canopy layer on winter heat islands using a mesoscale atmospheric model coupled with an urban canopy model. Numerical experiments indicate that snow cover in urban areas serves to decrease surface air temperature, with a stronger decrease in daily maximum temperatures (0.4-0.6°C) than daily minimum temperatures (0.1-0.3°C). The increase in surface albedo is primarily responsible for the decrease in net shortwave radiation and sensible heat flux. In addition, increased evaporation causes a weakened sensible heat flux. The estimated snow cover effect during the day is comparable with the typical magnitude of anthropogenic heat release. In urban canopy layer, snow cover on roofs plays a significant role in reducing surface air temperature. Snow clearing on roads tends to increase nocturnal surface air temperature, especially in suburban areas because decreased snow depth increases ground heat transfer. These results indicate that snow cover in urban canopy layer reduces surface air temperature, resulting in weakened urban heat islands.

The influence of seasonal snow on soil thermal and water dynamics under different vegetation covers in a permafrost region

Seasonal snow is one of the most important influences on the development and distribution of permafrost and the hydrothermal regime in surface soil. Alpine meadow, which constitutes the main land type in permafrost regions of the Qinghai-Tibet Plateau, was selected to study the influence of seasonal snow on the temperature and moisture in active soil layers under different vegetation coverage. Monitoring sites for soil moisture and temperature were constructed to observe the hydrothermal processes in active soil layers under different vegetation cover with seasonal snow cover variation for three years from 2010 to 2012. Differences in soil temperature and moisture in areas of diverse vegetation coverage with varying levels of snow cover were analyzed using active soil layer water and temperature indices. The results indicated that snow cover greatly influenced the hydrothermal dynamics of the active soil layer in alpine meadows. In the snow manipulation experiment with a snow depth greater than 15 cm, the snow cover postponed both the freeze-fall and thawrise onset times of soil temperature and moisture in alpine LC (lower vegetation coverage) meadows and of soil moisture in alpine HC (higher vegetation coverage) meadows; however, the opposite response occurred for soil temperatures of alpine HC meadows, where the entire melting period was extended by advancing the thaw-rise and delaying the freeze-fall onset time of the soil temperature. Snow cover resulted in a decreased amplitude and rate of variation in soil temperature, for both alpine HC meadows and alpine LC meadows, whereas the distinct influence of snow cover on the amplitude and rate of soil moisture variation occurred at different soil layers with different vegetation coverages. Snow cover increased the soil moisture of alpine grasslands during thawing periods. The results confirmed that the annual hydrothermal dynamics of active layers in permafrost were subject to the synergistic actions of both snow cover and vegetation coverage.

Modeling the influence of snow cover on low Arctic net ecosystem exchange

The Arctic net ecosystem exchange (NEE) of CO2 between the land surface and the atmosphere is influenced by the timing of snow onset and melt. The objective of this study was to examine whether uncertainty in model estimates of NEE could be reduced by representing the influence of snow on NEE using remote sensing observations of snow cover area (SCA). Observations of NEE and time-lapse images of SCA were collected over four locations at a low Arctic site (Daring Lake, NWT) in May–June 2010. Analysis of these observations indicated that SCA influences NEE, and that good agreement exists between SCA derived from time-lapse images, Landsat and MODIS. MODIS SCA was therefore incorporated into the vegetation photosynthesis respiration model (VPRM). VPRM was calibrated using observations collected in 2005 at Daring Lake. Estimates of NEE were then generated over Daring Lake and Ivotuk, Alaska (2004–2007) using VPRM formulations with and without explicit representations of the influence of SCA on respiration and/or photosynthesis. Model performance was assessed by comparing VPRM output against unfilled eddy covariance observations from Daring Lake and Ivotuk (2004–2007). The uncertainty in VPRM estimates of NEE was reduced when respiration was estimated as a function of air temperature when SCA ≤ 50% and as a function of soil temperature when SCA > 50%.

Influence of snow cover on the parameters flexural-gravity waves in ice cover

This paper presents a mathematical model for the analysis of the stress-strain state of ice cover in the presence of a snow layer under dynamic loads. Numerical calculations were made using the model of indestructible ice, and the results were compared with experimental data.

Mast seeding in deciduous forests of the northern Apennines (Italy) and its influence on wild boar population dynamics

Pulsed food resources may strongly affect the population dynamics of several consumer species, with consequences on the ecosystem. One of the most common pulsed resources is forest mast seeding. We analysed mast seeding in deciduous forests in a mountainous area of northern Apennines and its effect on population dynamics of wild boar (Sus scrofa L.). We performed a quantitative, 20-year analysis on annual seed production in Turkey oak (Quercus cerris L.), beech (Fagus sylvatica L.) and chestnut (Castanea sativa Mill.) forest stands using litter traps. The wild boar population density was estimated by means of drive censuses and hunting bag records. The role of other biotic (density of predators) and abiotic (climate) factors potentially affecting wild boar mortality was also investigated. Turkey oak and chestnut showed high levels of seed production, whereas lower levels were found in beech. The pulsed resources of chestnut and Turkey oak positively affected piglet density. Analyses also highlighted the influence of snow cover and wolves on wild boar population dynamics. Wild boar can be considered a pulse rate species, the management of which can be improved by annual monitoring of seed production.

Influence of snow-cover and soil-frost variations on continuously monitored CO2 flux from agricultural land

Changes in cryospheric snow accumulation, snowmelt, and soil freezing and thawing might influence the ground-surface CO2 flux and cumulative winter CO2 flux from agricultural land. We continuously observed CO2 flux using automatically closing chambers at an untreated control plot and a plot with snow removal in northern Japan. The CO2 in soil pores at 10-cm depth increased by 6.5ppmvday−1 as soil began to freeze, but it increased dramatically (to 49ppmvday−1) after snowmelt water infiltrated the soil and froze. The soil-frost layer constrained gas diffusion into the air, and the barrier strengthened as the frozen snowmelt water decreased the air volume in soil pores. Leached gas CO2 from the freezing snowmelt water also increased gas CO2 concentration in soil. As the soil thawed, the CO2 concentration decreased drastically, at 790ppmvday−1. However, these changes had little effect on CO2 flux. The soil CO2 concentration remained stable after snow cover reached 30cm in the control plot. Low CO2 flux in both plots occurred during the winter. No clear relation was found between CO2 flux and snow depth or soil-frost depth because of the small CO2 source at this site. We also considered how the presence of the chamber influenced soil temperatures and water contents. During the snow-free season, the chamber mitigated diurnal changes in soil temperature. The daily average soil temperature differed from that in the natural state by −1.7°C to 6.3°C. This fluctuation of temperature corresponded to the fluctuation of CO2 flux, which ranged from 91% to 143% of the CO2 flux in the natural state based on the temperature-response equations. The chamber had little influence on the soil temperature during the snow-cover period, and did not influence soil water content throughout the study period. Cumulative winter CO2 emissions were 17.2gCm−2 (over 143 days) in the control plot and 13.4gCm−2 (over 151 days) in the treated plot (10.0 and 7.5% of annual accumulation, respectively).

Influence of snow cover and grain size on the ground thermal regime in the discontinuous permafrost zone, Swiss Alps

The presence or absence of frozen ground within the discontinuous mountain permafrost zone is on a small scale largely determined by local site characteristics. Snow cover changes spatially at short distances caused by relief and temporally from year to year. Substrate grain size influences the heat exchange processes between air and surface and causes differences in the ground thermal properties. Based on data of four shallow boreholes and 25 temperature loggers, the effect of these factors on the ground thermal regime in two recently deglaciated forefields in the Engadin, Swiss Alps is investigated. The annual depth of the cold wave is dependent on the characteristics of the snow cover and can be twice as deep in winters with a snow height below 0.8m. In contrast, the active layer thickness is constant even though the duration of the snow-free period changes substantially from year to year. A difference in mean annual ground surface temperatures of 4.3°C is registered over distances of 50m. The postulated negative thermal anomaly in blocky surfaces is confirmed by our data. However, permafrost conditions are also recorded at one site with fine-grained debris (sand/gravel) that is attributed to its geomorphological position and a strong coupling between air and ground surface temperatures in early winter. Thus, the ground thermal regime shows a large spatial and temporal variability as a function of snow cover evolution, snow height, surface substrate, and relief. The short data record does not yet enable us to detect any climatic signal within the discontinuous permafrost.

Altitudinal temperature lapse rates in an Alpine valley: trends and the influence of season and weather patterns

AbstractThe vertical temperature structure in the area of Garmisch‐Partenkirchen between the Loisach river valley and the highest mountain in Germany (Zugspitze, 2962 m a.s.l.) is analysed. Using long time series (1936–2008) of daily mean, minimum and maximum temperatures from two meteorological stations, in the valley floor and on the mountain top, we studied seasonal variations in temperature lapse rates. By using daily data on weather types, significantly different altitudinal temperature lapse rates and daily temperature ranges for low and high pressure weather situations were found. There was no significant influence of snow cover in the valley on the lapse rate. At both stations, there has been an increase in temperature during recent decades. As there was a slight difference between these trends, the lapse rate has tended to become more negative, i.e. the difference between the mountain top and the valley has become more pronounced. In order to investigate the lapse rates in more detail, unpublished temperature data from 1989 to 1990 on slope transects near Garmisch‐Partenkirchen were evaluated. Despite the fact that an exact description of the vertical structure of the atmospheric temperature is possible only from free air measurements, there are some indications that major inversions occur in the first 500 m above the valley ground, depending on season, weather situation and time of day. Copyright © 2012 Royal Meteorological Society

Statistical modelling of ground temperature in mountain permafrost

Permafrost consists of soil and rocks that remain at 0 ° C or below for at least two consecutive years. In mountains, permafrost ground ice acts like cement, stabilizing rock walls. Its degradation, following climate warming, may lead to slope instability in high mountains and damage to infrastructure, so knowledge about its evolution is essential for risk analysis. In pure solids, heat is transferred by conduction, but permafrost ground is also subject to non-conductive fluxes, and heat transfers are influenced by factors such as air temperature and snow cover, so a deterministic scheme cannot fully describe heat propagation. Current approaches to modelling use numerical models involving heat conduction schemes and energy balance models, requiring data on quantities such as relative humidity and radiation. We describe a stochastic treatment of the heat equation, which adapts to space–time changes in heat transfers driven by factors such as air temperature and snow cover, without requiring corresponding data, as part of a statistical model. The flexibility and performance of our approach are illustrated using data from two boreholes in the Swiss Alps, which show the strong influence of snow cover on ground temperature and the long-term degradation of permafrost produced by the 2003 heat wave.

Comparison of visual‐based helicopter and fixed‐wing forward‐looking infrared surveys for counting white‐tailed deer Odocoileus virginianus

AbstractAerial surveys using direct counts of animals are commonly used to estimate deer abundance. Forward‐looking infrared (FLIR) technology is increasingly replacing traditional methods such as visual observation from helicopters. Our goals were to compare fixed‐wing FLIR and visual, helicopter‐based counts in terms of relative bias, influence of snow cover and cost. We surveyed five plots: four 41.4 km2 plots with free‐ranging white‐tailed deer Odocoileus virginianus populations in Wisconsin and a 5.3 km2 plot with a white‐tailed deer population contained by a high fence in Michigan. We surveyed plots using both fixed‐wing FLIR and helicopters, both with snow cover and without snow. None of the methods counted more deer than the other when snow was present. Helicopter counts were lower in the absence of snow, but lack of snow cover did not apparently affect FLIR. Group sizes of observed deer were similar regardless of survey method or season. We found that FLIR counts were generally precise (CV = 0.089) when two or three replicate surveys were conducted within a few hours. However, at the plot level, FLIR counts differed greatly between seasons, suggesting that detection rates vary over larger time scales. Fixed‐wing FLIR was more costly than visual observers in helicopters and was more restrictive in terms of acceptable survey conditions. Further research is needed to understand what factors influence the detection of deer during FLIR surveys.