Snow Duration Research Articles

The Andes Cordillera. Part II: Rio Olivares Basin snow conditions (1979–2014), central Chile

ABSTRACTSnow cover extent, duration, and properties were simulated (1979/1980–2013/2014) for the Rio Olivares Basin (548 km2) in central Chilean Andes, in an effort to understand conditions and trends (linear) at a basin scale. The National Aeronautics and Space Administration Modern‐Era Retrospective Analysis for Research and Applications products, together with the snow modelling software package SnowModel allowed simulations of first‐order atmospheric forcings (mean annual air temperature (MAAT) and water‐equivalent precipitation) and terrestrial snow features (snow cover extent, duration, snow water‐equivalent depth, snow density, and runoff generated from snow melt). Simulated snow cover extent and depletion curves were verified against Moderate Resolution Imaging Spectroradiometer‐derived snow cover data. For the Rio Olivares Basin, MAAT was −2.9 ± 0.6 °C with a mean 0° isotherm at 3325 m a.s.l. The greatest temporal and spatial changes in temperature over the 35‐year period occurred in January and at the highest elevations, respectively. Mean annual precipitation was 1.86 ± 0.60 m w.e., indicating an increase in precipitation of ∼0.1 m w.e. 100 m−1 increase in elevation. On average, ∼90% of the basin precipitation fell as snow, varying from 70% at ∼2600 m a.s.l., to 95% at ∼4200 m a.s.l. In 20 out of 35 years the snow cover extent went to 0% (no basin snow cover) by end‐of‐summer (during March), and the snow duration increased on average by ∼10 days 100 m−1 increase in elevation. Approximately 85% of the basin outlet freshwater runoff originated from snowmelt, making snowmelt a dominant contributor to water resources. Snowmelt‐derived basin runoff was dominated by variability in snow precipitation rather than by variability in MAAT.

Snow cover evolution, on 2009-2014, at the Limnopolar Lake CALM-S site on Byers Peninsula, Livingston Island, Antarctica.

In February 2009, a new Circumpolar Active Layer Monitoring (CALM) site was established in the Limnopolar Lake drainage basin, in Byers Peninsula, Livingston Island (South Shetland Archipelago), Antarctica (62°38′59.1″S, 61°06′16.9″W). The first results from active layer thickness and thermal monitoring reported interannual variations, without relevant changes in the air temperature conditions, leaving the snow cover as the most suitable agent controlling the reported changes. Here we study in detail the snow cover evolution on thickness, timing and duration during the 2009–2014 period, by the analysis of mean daily air and ground surface temperature, as well as the snow depth monitored in a stake. Freezing indexes, n-factor, and snow indexes calculations were analyzed to establish the effects of snow cover on the ground thermal regime. The evolution of the snow cover during the 2009–2014 period resulted in about similar snow depths, with mean values of about 45cm. The snow onset remained about constant with small variations of 10days in early March. However, the snow offset had significant variations, increasing in more than 60days in the last three years. This delay on the snow offset resulted in an increase in the snow cover duration from 267 (2011) to 338 (2014) days. Air temperature seems not to be strongly involved in this snow cover timing variation since the highest variation on this period of the maximum and mean annual temperatures only diminished, about 1.6° and 0.5° C respectively, but remaining constant the minimum temperatures (between −12° and −18°C). In consequence, the surface temperature evolved to become less variable along the year directly related to the annual snow layer duration, trending to longer zero curtain periods. In conclusion, the increase in the snow duration is resulting in a reduction of the thaw period in the ground, but remaining similar snow cover onset dates. The consequent decrease in the snow-free period each year could result in a thinner active layer.

The role of lake effect snow cover in reducing the susceptibility of Miscanthus × giganteus to extreme cold soil temperatures in Michigan

Miscanthus×giganteus (hereafter “M.×giganteus”) is a low-input, highly productive perennial grass increasingly grown in the US Midwest for conversion into cellulosic ethanol. M.×giganteus must be propagated rhizomatously because it is a sterile hybrid, and because it is a perennial crop, mass die-offs may take two to three years to recover fully. This leads to economic loss and interruption of bioenergy supply. Several experimental M.×giganteus crops in Illinois and Wisconsin experienced mass mortality due to extreme cold soil temperatures in the winter of 2008–2009. During this same winter, experimental M.×giganteus crops in Michigan experienced little to no mortality. It is hypothesized that the insulating effect of increased snow depth and duration due to lake effect snowfall is sufficient to reduce the risk of cold-induced M.×giganteus mortality in the Lower Peninsula of Michigan, where the opportunity cost of farmland is also lower than in other parts of the US Midwest. Observations of air and soil temperatures from experimental M.×giganteus plots in Illinois, Wisconsin, and Michigan are analyzed during periods of snow cover and no snow cover in two anomalously cold winters, and a synoptic analysis is also presented. It is found that the absolute difference between the shallow soil temperature and air temperature was 3–7°C greater when there was at least 2.5cm of snow on the ground at these sites. However, shallow soil temperatures were observed to drop below laboratory mortality temperature thresholds of M.×giganteus (−3°C and −6.5°C) despite snow cover, demonstrating that snowfall alone should not be relied upon to sufficiently insulate M.×giganteus rhizomes during their winter dormancy. Additionally, seven winters of shallow soil temperature observations at 12 sites in Michigan are compared with satellite-derived estimates of snow cover and it is shown that increased snow cover depth may not lead to decreased likelihood of soil temperatures below −3°C.

Observed contrast changes in snow cover phenology in northern middle and high latitudes from 2001-2014.

Quantifying and attributing the phenological changes in snow cover are essential for meteorological, hydrological, ecological, and societal implications. However, snow cover phenology changes have not been well documented. Evidence from multiple satellite and reanalysis data from 2001 to 2014 points out that the snow end date (De) advanced by 5.11 (±2.20) days in northern high latitudes (52–75°N) and was delayed by 3.28 (±2.59) days in northern mid-latitudes (32–52°N) at the 90% confidence level. Dominated by changes in De, snow duration days (Dd) was shorter in duration by 5.57 (±2.55) days in high latitudes and longer by 9.74 (±2.58) days in mid-latitudes. Changes in De during the spring season were consistent with the spatiotemporal pattern of land surface albedo change. Decreased land surface temperature combined with increased precipitation in mid-latitudes and significantly increased land surface temperature in high latitudes, impacted by recent Pacific surface cooling, Arctic amplification and strengthening westerlies, result in contrasting changes in the Northern Hemisphere snow cover phenology. Changes in the snow cover phenology led to contrasting anomalies of snow radiative forcing, which is dominated by De and accounts for 51% of the total shortwave flux anomalies at the top of the atmosphere.

Observations of distributed snow depth and snow duration within diverse forest structures in a maritime mountain watershed

AbstractSpatially distributed snow depth and snow duration data were collected over two to four snow seasons during water years 2011–2014 in experimental forest plots within the Cedar River Municipal Watershed, 50 km east of Seattle, Washington, USA. These 40 × 40 m forest plots, situated on the western slope of the Cascade Range, include unthinned second‐growth coniferous forests, variable density thinned forests, forest gaps in which a 20 m diameter (approximately equivalent to one tree height) gap was cut in the middle of each plot, and old‐growth forest. Together, this publicly available data set includes snow depth and density observations from manual snow surveys, distributed snow duration observations from ground temperature sensors and time‐lapse cameras, meteorological data collected at two open locations and three forested locations, and forest canopy data from airborne light detection and ranging (LiDAR) data and hemispherical photographs. These colocated snow, meteorological, and forest data have the potential to improve understanding of forest influences on snow processes, and provide a unique model‐testing data set for hydrological analyses in a forested, maritime watershed. We present empirical snow depletion curves within forests to illustrate an application of these data to improve subgrid representation of snow cover in distributed modeling.

Usnea antarctica, an important Antarctic lichen, is vulnerable to aspects of regional environmental change

Studies of cryptogam responses to climate change in the polar regions are scarce because these slow-growing organisms require long-term monitoring studies. Here, we analyse the response of a lichen and moss community to 10 years of passive environmental manipulation using open-top chambers (OTCs) in the maritime Antarctic region. Cover of the dominant lichen Usnea antarctica declined by 71 % in the OTCs. However, less dominant lichen species showed no significant responses except for an increase in Ochrolechia frigida, which typically covered dying lichen and moss vegetation. There were no detectable responses in the moss or associated micro-arthropod communities to the influence of the OTCs. Based on calculated respiration rates, we hypothesise that the decline of U. antarctica was most likely caused by increased net winter respiration rates (11 %), driven by the higher temperatures and lower light levels experienced inside the OTCs as a result of greater snow accumulation. During summer, U. antarctica appears unable to compensate for this increased carbon loss, leading to a negative carbon balance on an annual basis, and the lichen therefore appears to be vulnerable to such climate change simulations. These findings indicate that U. antarctica dominated fell-fields may change dramatically if current environmental change trends continue in the maritime Antarctic, especially if associated with increases in winter snow depth or duration.

Influence of terrain aspect on water partitioning, vegetation structure and vegetation greening in high‐elevation catchments in northern New Mexico

AbstractWe investigated vegetation structure, water partitioning dynamics and vegetation greening from 2000 through 2012 in three catchments draining north and east aspects of Redondo Peak in northern New Mexico. Vegetation structure was quantified from 1‐m lidar data, while vegetation greening was quantified using remotely sensed normalized difference vegetation index (NDVI). Hydrological partitioning at the catchment scale was estimated with a metric of catchment‐scale water fluxes and vegetation water use [Horton index (HI)]. The predominantly north‐facing catchment, when compared with the other two eastern catchments, receives less solar radiation, exhibits less forest cover and smaller biomass and has more surface run‐off (~15% of P) as a consequence of a smaller vaporization (85% of P) and smaller vegetation water consumption (HI = 0·85). Moreover, the north‐facing catchment showed smaller peak NDVI values (5·98) and shorter growing season length (121 days) as a consequence of energy limitation. In contrast, the two eastern catchments receive larger solar radiation and have more biomass and forest cover (>76%), smaller surface run‐off (<10% P) and higher vaporization (>90% P) and vegetation water consumption (HI = 0·95). The eastern catchments had larger vegetation greening (6·28–6·58) and a longer growing season (148–160 days). Snowpack conditions, such as maximum snow water equivalent and duration of the snow on the ground, explain over 95% of water partitioning (HI) that in turn influenced annual vegetation greening (R2 = 0·48–0·67; p < 0·05). This catchment‐scale study in perennial streams indicates that terrain aspect at a similar altitude (2700–3435 m) strongly controls energy, water distribution and vegetation productivity in high‐elevation ecosystems. Copyright © 2015 John Wiley & Sons, Ltd.

Changes in the snow water equivalent in mountainous basins in Slovakia over recent decades

Abstract. Changes in snowpack and duration of snow cover can cause changes in the regime of snow and rain-snow induced floods. The recent IPCC report suggests that, in snow-dominated regions such as the Alps, the Carpathian Mountains and the northern parts of Europe, spring snowmelt floods may occur earlier in a future climate because of warmer winters, and flood hazards may increase during wetter and warmer winters, with more frequent rain and less frequent snowfall. The monitoring and modelling of snow accumulation and snow melting in mountainous catchments is rather complicated, especially due to the high spatial variability of snow characteristics and the limited availability of terrestrial hydrological data. An evaluation of changes in the snow water equivalent (SWE) during the period of 1961–2010 in the Upper Hron river basin, which is representative of the mountainous regions in Central Slovakia, is provided in this paper. An analysis of the snow cover was performed using simulated values of the snow water equivalent by a conceptual semi-distributed hydrological rainfall-runoff model. Due to the poor availability of the measured snow water equivalent data, the analysis was performed using its simulated values. Modelling of the SWE was performed in different altitude zones by a conceptual semi-distributed hydrological rainfall-runoff model. The evaluation of the results over the past five decades indicates a decrease in the simulated snow water equivalent and the snow duration in each altitude zone and in all months of the winter season. Significant decreasing trends were found for December, January and February, especially in the highest altitude zone.

Impact of Climate Change on Life and Livelihood of Indigenous People of Higher Himalaya in Uttarakhand, India

Increase in average temperatures and abrupt changes in the precipitation regime are perceived to take place in the region by most people. Duration, amount and form of atmospheric precipitation is reported to have changed significantly. Even during winters the people of the region are increasingly getting overwhelmed with liquid precipitation rather than solid precipitation that was traditionally recived in the form of snow. This is perceived to be responsible for reduced duration of snow in the region. This is held responsible for reduced water availability in the region and people have already started to face scarcity of water. Most people of the region at the same time agree that there are changes in the timing of flowering and fruiting of plants. Productivity of the agricultural fields is also reported to have decreased. Increased incidences of pest infestations and animal attacks are also reported from the region. These have forced the inhabitants to introduce many changes in their traditional life support pursuits. Of these some are identified as being part of the coping strategy of the people of the region that is witnessing climate induced changes at an alarming rate. These are required to be studied, documented, researched and improvised with appropriate inputs from formal science and technology so as to make these viable and acceptable to the masses.

Winter Conditions and Land Cover Structure the Subnivium, A Seasonal Refuge beneath the Snow.

In seasonally snow-covered environments, many organisms endure winter by using the subnivium, a below-snow thermally stable seasonal refugium. Because the insulation of snow is dependent on snow depth and density, the stability of temperatures within the subnivium varies across land cover types. Additionally, across much of the Northern Hemisphere snow extent, depth and duration are generally decreasing while snow density is increasing due to climate change. These changes are likely to destabilize the thermal profile of the subnivium, although they have not yet been quantified. To explore the effects of land cover and climate change on the subnivium, we measured snow pack characteristics (depth and density), and ambient and subnivium temperatures from three different land cover types (prairie, deciduous forest, and coniferous forest) and within a micro-greenhouse (2.5 x 2.5 x 2 m) that maintained a temperature of 5°C warmer than outdoor ambient temperatures, and automatically opened during snow events throughout the winter of 2013/14. We found that the mean daily subnivium temperature was significantly colder in the deciduous cover type than the prairie cover type, and that prairie had higher maximum subnivium temperatures than both of the other cover types. Our climate change simulation revealed that, although ambient temperatures within the micro-greenhouse were 5°C warmer than outside the greenhouse, the daily minimum subnivium temperature was significantly lower inside the greenhouse. Our findings suggest that climate change could have considerable effects on the refuge quality of the subnivium, and that some cover types appear to be more susceptible to these effects than others.

Evaluating observational methods to quantify snow duration under diverse forest canopies

AbstractForests cover almost 40% of the seasonally snow‐covered regions in North America. However, operational snow networks are located primarily in forest clearings, and optical remote sensing cannot see through tree canopies to detect forest snowpack. Due to the complex influence of the forest on snowpack duration, ground observations in forests are essential. We therefore consider the effectiveness of different strategies to observe snow‐covered area under forests. At our study location in the Pacific Northwest, we simultaneously deployed fiber‐optic cable, stand‐alone ground temperature sensors, and time‐lapse digital cameras in three diverse forest treatments: control second‐growth forest, thinned forest, and forest gaps (one tree height in diameter). We derived fractional snow‐covered area and snow duration metrics from the colocated instruments to assess optimal spatial resolution and sampling configuration, and snow duration differences between forest treatments. The fiber‐optic cable and the cameras indicated that mean snow duration was 8 days longer in the gap plots than in the control plots (p < 0.001). We conducted Monte Carlo experiments for observing mean snow duration in a 40 m forest plot, and found the 95% confidence interval was ±5 days for 10 m spacing between instruments and ±3 days for 6 m spacing. We further tested the representativeness of sampling one plot per treatment group by observing snow duration across replicated forest plots at the same elevation, and at a set of forest plots 250 m higher. Relative relationships between snow duration in the forest treatments are consistent between replicated plots, elevation, and two winters of data.

Microhabitat use by mountain pygmy‐possum (Burramys parvus): Implications for the conservation of small mammals in alpine environments

AbstractThe Australian alpine region harbours a wide range of species, many of which are endemic and of high conservation value. Among these species, the endangered mountain pygmy‐possum, Burramys parvus, is of particular interest because this specialized marsupial is highly sensitive to extreme temperatures. The selection of microhabitats by B. parvus is a critical but poorly understood element of its biological characteristics. To understand the microhabitat preferences of B. parvus, we performed detailed investigations of the thermal properties of alpine boulder fields. The selection of a preferred microclimate was demonstrated by comparing temperatures and environmental conditions in preferred and non‐preferred boulder fields. The variability of the daily temperature depended on the depth at which measurements were made within the boulder fields. Temperatures were more stable as depth increased. The results suggest that B. parvus prefers to occupy deep boulder fields at high elevations with good rock structure (small rock and cavity size with multiple layers) and long snow duration because these boulder fields can provide a favourable microclimate. At 1 m depth, the maximum temperatures in the hottest part of the year were 1.27°C cooler in preferred compared to non‐preferred boulder fields. In the coldest part of the year, immediately following the melting of persistent snow cover, the minimum temperatures at a depth of 1 m were 1.67°C warmer in preferred compared to non‐preferred boulder fields. On average, the snow duration was 27 days greater in the boulder fields preferred by B. parvus than in non‐preferred boulder fields. Our results emphasize the value of boulder field microhabitats as thermal refuges for small mammals in rocky habitats within alpine environments in the light of continuing habitat loss and climate change.

川西亚高山森林林窗不同时期土壤转化酶和脲酶活性的特征

As an important small scale disturbance,forest gaps are often considered to be major drivers in the natural forest regeneration. Moreover,forest gaps can play essential roles in soil processes including the dynamics of soil enzyme activity,since the snow,precipitation and sunshine duration could be redistributed in different gap location due to the effects of forest canopy. Subalpine forest in western Sichuan is a typical cold biome,which often displays sensitive responses to environment disturbance because of its fragile characters. As yet,more and more recent studies have concentrated on gap characteristics and seedling regeneration processes in this area,but little attention has been given to the effects of forest gap on soil enzyme activity. As we know,soil invertase and urease are the key enzymes involved in the soil organic carbon and nitrogen transformation,respectively,and the changes of their activities are closely associated with the carbon and nitrogen cycling. Therefore,to understand the effects of forest gap on soil invertase and urease activities at different seasons in alpine forest,a field experiment was conducted in a Picea asperata plantation forest in western Sichuan. The dynamics of soil invertase and urease activity under gap center,gap edge and under-canopy were investigated from June 2012 to May 2013.Soil samples in soil organic layer and mineral soil layer were collected in growing season( completely soil thawing stage,early stage and later stage of growing season) and freeze-thaw season( onset stage of freezing,deeply soil freezing stage and soil thawing stage). The results showed that soil invertase activity in soil organic layer was higher than that in mineral soil layer regardless of forest gap location. Soil invertase activity during the growing season in both soil organic layer and mineral soil layer showed the order: gap center under-canopy gap edge,but soil urease activity showed the order: gap center gap edge under-canopy. In comparison with gap edge and under-canopy,gap center exhibited higher soil invertase activity at onset stage of freezing and deeply soil freezing stage,while soil invertase activity in under-canopy was higher than that of gap center and gap edge at soil thawing stage. In addition,soil urease activity at onset stage of freezing and soil thawing stage was significantly higher in under-canopy than that in gap center and gap edge,although which at deeply soil freezing stage showed few differences in different gap locations. The results here imply that gap location has a profound impact on soil invertase and urease activities at different seasons in subalpine forest.

A Hidden Markov Model for avalanche forecasting on Chowkibal–Tangdhar road axis in Indian Himalayas

A numerical avalanche prediction scheme using Hidden Markov Model (HMM) has been developed for Chowkibal–Tangdhar road axis in J&K, India. The model forecast is in the form of different levels of avalanche danger (no, low, medium, and high) with a lead time of two days. Snow and meteorological data (maximum temperature, minimum temperature, fresh snow, fresh snow duration, standing snow) of past 12 winters (1992–2008) have been used to derive the model input variables (average temperature, fresh snow in 24 hrs, snow fall intensity, standing snow, Snow Temperature Index (STI) of the top layer, and STI of buried layer). As in HMMs, there are two sequences: a state sequence and a state dependent observation sequence; in the present model, different levels of avalanche danger are considered as different states of the model and Avalanche Activity Index (AAI) of a day, derived from the model input variables, as an observation. Validation of the model with independent data of two winters (2008–2009, 2009–2010) gives 80% accuracy for both day-1 and day-2. Comparison of various forecasting quality measures and Heidke Skill Score of the HMM and the NN model indicate better forecasting skill of the HMM.

Below-cloud scavenging of aerosol particles by precipitation in a typical valley city, northwestern China

To fill the blank information for aerosol precipitation-scavenging research in north-west of China, the aerosol particle and raindrop size distributions were measured simultaneously during 1 September 2012 to 31 August 2013 in urban Lanzhou. The scavenging coefficients of thunderstorm and non-thunderstorm rain and snow events were studied and presented on the basis of nine selected precipitation cases including 3 snow and 6 rain events. The variation of scavenging coefficients of snowfall across the size distribution clearly exhibited a trough of lower values for particles of 1000 nm–2000 nm in diameter, while the particles smaller than 500 nm were scavenged efficiently by non-thunderstorm rain, and thunderstorm rain more effectively scavenged the particles in 500–1000 nm. The snow scavenging coefficients varied between 3.11 × 10−7 s−1 and 1.18 × 10−3s−1 in the 10–10,000 nm size range. The scavenging coefficients of thunderstorm (non-thunderstorm) rain were between 8.25 × 10−7s−1 (7.48 × 10−6s−1) and 1.23 × 10−3s−1 (7.46 × 10−4s−1). Additionally, the number of particles in 10–50 nm was more sensitive to duration of snow, while snowfall intensity was more responsible for particle number concentrations in 50–100 nm and 100–1000 nm. The longer period of precipitation with lower raindrop velocity can more effectively scavenge the particles in the size range of 10–50 nm.

Changes in winter conditions impact forest management in north temperate forests

Climate change may impact forest management activities with important implications for forest ecosystems. However, most climate change research on forests has focused on climate-driven shifts in species ranges, forest carbon, and hydrology. To examine how climate change may alter timber harvesting and forest operations in north temperate forests, we asked: 1) How have winter conditions changed over the past 60 years? 2) Have changes in winter weather altered timber harvest patterns on public forestlands? 3) What are the implications of changes in winter weather conditions for timber harvest operations in the context of the economic, ecological, and social goals of forest management? Using meteorological information from Climate Data Online and Autoregressive Integrated Moving Average (ARIMA) models we document substantial changes in winter conditions in Wisconsin, including a two- to three-week shortening of frozen ground conditions from 1948 to 2012. Increases in minimum and mean soil temperatures were spatially heterogeneous. Analysis of timber harvest records identified a shift toward greater harvest of jack pine and red pine and less harvest of aspen, black spruce, hemlock, red maple, and white spruce in years with less frozen ground or snow duration. Interviews suggested that frozen ground is a mediating condition that enables low-impact timber harvesting. Climate change may alter frozen ground conditions with complex implications for forest management.

Interaction of thermal and mechanical processes in steep permafrost rock walls: A conceptual approach

Degradation of permafrost rock wall decreases stability and can initiate rock slope instability of all magnitudes. Rock instability is controlled by the balance of shear forces and shear resistances. The sensitivity of slope stability to warming results from a complex interplay of shear forces and resistances. Conductive, convective and advective heat transport processes act to warm, degrade and thaw permafrost in rock walls. On a seasonal scale, snow cover changes are a poorly understood key control of the timing and extent of thawing and permafrost degradation. We identified two potential critical time windows where shear forces might exceed shear resistances of the rock. In early summer combined hydrostatic and cryostatic pressure can cause a peak in shear force exceeding high frozen shear resistance and in autumn fast increasing shear forces can exceed slower increasing shear resistance. On a multiannual system scale, shear resistances change from predominantly rock-mechanically to ice-mechanically controlled. Progressive rock bridge failure results in an increase of sensitivity to warming. Climate change alters snow cover and duration and, hereby, thermal and mechanical processes in the rock wall. Amplified thawing of permafrost will result in higher rock slope instability and rock fall activity. We present a holistic conceptual approach connecting thermal and mechanical processes, validate parts of the model with geophysical and kinematic data and develop future scenarios to enhance understanding on system scale.

Change of Snow Cover and Its Impact on Alpine Vegetation in the Source Regions of Large Rivers on the Qinghai-Tibetan Plateau, China

Based on a Normalized Difference Vegetation Index (NDVI) and remote sensing data of snow cover, we analyzed the variation in NDVI in relation to trends in snow cover and vegetation of the source regions of large rivers on the Qinghai-Tibetan Plateau. We then calculated the relationship between snow cover duration, snow depth, and NDVI to reveal the effect of snow cover change on vegetation growth on a regional scale. The results show that both snow depth and duration tend to reduce gradually from northeast to southwest on the Qinghai-Tibetan Plateau. Furthermore, snow cover duration (snow depth > 0 cm) has high interannual fluctuation and generally shows an increasing trend (P < 0.01) from 1980 to 2004. The interannual fluctuations of the duration of days with snow depth ≥ 5 cm as well as the maximum and average snow depth are also quite high, but they generally show insignificant tendencies (P > 0.05) from 1980 to 2004. The snow cover characteristics (duration and depth) are insignificantly correlated to annual maximum NDVI. However, a significant positive correlation (P < 0.05) is observed between snow cover duration (snow depth > 0 cm) and the NDVI values of both April and July, and an obvious negative correlation (P < 0.05) is observed between snow depth and the NDVI value in October across all source regions from 1981 to 2004. In the study area, increasing snow depth and the prolongation of the duration of snow cover have adverse effects on vegetation growth the following year. The melting of snow brings increasing effects to the NDVI value in the spring.

Effect of snow depth and snow duration on soil N dynamics and microbial activity in the alpine areas of the eastern Tibetan Plateau

The effects of snow regimes (including the depth and duration of snow cover) on soil N dynamics and microbial activity in situ were explored in the alpine belt of the eastern Tibetan Plateau. Deeper snow-cover reduced NH 4 + -N content, microbial biomass carbon and nitrogen, fungi count, and enzyme activities, whereas did not change net N mineralization. No differences in N pools in the soil, microbial biomass, microbial counts, and enzyme activity were found under the different duration of snow cover, showing that accumulation and release in soil N pools did not be significantly changed by earlier continuous snow cover.

Shifting mountain snow patterns in a changing climate from remote sensing retrieval

Observed climate change has already led to a wide range of impacts on environmental systems and society. In this context, many mountain regions seem to be particularly sensitive to a changing climate, through increases in temperature coupled with changes in precipitation regimes that are often larger than the global average (EEA, 2012). In mid-latitude mountains, these driving factors strongly influence the variability of the mountain snow-pack, through a decrease in seasonal reserves and earlier melting of the snow pack. These in turn impact on hydrological systems in different watersheds and, ultimately, have consequences for water management. Snow monitoring from remote sensing provides a unique opportunity to address the question of snow cover regime changes at the regional scale. This study outlines the results retrieved from the MODIS satellite images over a time period of 10 hydrological years (2000–2010) and applied to two case studies of the EU FP7 ACQWA project, namely the upper Rhone and Po in Europe and the headwaters of the Syr Darya in Kyrgyzstan (Central Asia). The satellite data were provided by the MODIS Terra MOD-09 reflectance images (NASA) and MOD-10 snow products (NSIDC). Daily snow maps were retrieved over that decade and the results presented here focus on the temporal and spatial changes in snow cover. This paper highlights the statistical bias observed in some specific regions, expressed by the standard deviation values (STD) of annual snow duration. This bias is linked to the response of snow cover to changes in elevation and can be used as a signal of strong instability in regions sensitive to climate change: with alternations of heavy snowfalls and rapid snow melting processes. The interest of the study is to compare the methodology between the medium scales (Europe) and the large scales (Central Asia) in order to overcome the limits of the applied methodologies and to improve their performances. Results show that the yearly snow cover duration increases by 4–5days per 100m elevation during the accumulation period, depending of the watershed, while during the melting season the snow depletion rate is 0.3% per day of surface loss for the upper Rhone catchment, 0.4%/day for the Syr Darya headwater basins, and 0.6%/day for the upper Po, respectively. Then, the annual STD maps of snow cover indicate higher values (more than 45days difference compared to the mean values) for (i) the Po foothill region at medium elevation (SE orientation) and (ii) the Kyrgyzstan high plateaux (permafrost areas). These observations cover only a time-period of 10years, but exhibit a signal under current climate that is already consistent with the expected decline in snow in these regions in the course of the 21st century.