Snow Depth (snow + depth)

Distribution by Scientific Domains


Selected Abstracts


Needle traits of an evergreen, coniferous shrub growing at wind-exposed and protected sites in a mountain region: does Pinus pumila produce needles with greater mass per area under wind-stress conditions?

PLANT BIOLOGY, Issue 2009
S. Nagano
Abstract Snow depth is one of the most important determinants of vegetation, especially in mountainous regions. In such regions, snow depth tends to be low at wind-exposed sites such as ridges, where stand height and productivity are limited by stressful environmental conditions during winter. Siberian dwarf pine (Pinus pumila Regel) is a dominant species in mountainous regions of Japan. We hypothesized that P. pumila produces needles with greater mass per area at wind-exposed sites than at wind-protected sites because it invests more nitrogen (N) in cell walls at the expense of N investment in the photosynthetic apparatus, resulting in increased photosynthetic N use efficiency (PNUE). Contrary to our hypothesis, plants at wind-exposed site invested less resources in needles, as exhibited by lower biomass, N, Rubisco and cell wall mass per unit area, and had higher photosynthetic capacity, higher PNUE and shorter needle life-span than plants at a wind-protected site. N partitioning was not significantly different between sites. These results suggest that P. pumila at wind-exposed sites produces needles at low cost with high productivity to compensate for a short leaf life-span, which may be imposed by wind stress when needles appear above the snow surface in winter. [source]


A study on the effect of Eurasian snow on the summer monsoon circulation and rainfall using a spectral GCM

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2006
S. K. Dash
Abstract Many studies based on observed data indicate the inverse relationship between the Eurasian snow cover/depth and the Indian summer monsoon rainfall (ISMR). The purpose of this study is to confirm the inverse snow,ISMR relationship by using the observed snow depth data as boundary conditions in the spectral general circulation model (GCM) of Indian Institute of Technology, Delhi (IITD), and to examine the influence of Eurasian snow depth on the monsoon circulation. The original model belonging to the European Centre for Medium range Weather Forecasts (ECMWF) at resolution T21 has been modified extensively to a higher resolution of T80L18 at IITD. A two-dimensional Lanczos digital filter has been used to represent the orography realistically. The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used for conducting sensitivity experiments using the above model. Two sensitivity experiments have been designed, corresponding to two contrasting cases: one with high Eurasian snow depth in spring followed by deficient ISMR and the second with low snow depth followed by excess ISMR. The difference fields of mean monsoon circulation simulated in the above two experiments are examined in detail in order to confirm the influence of Eurasian snow depth on ISMR and to examine the Asian summer monsoon circulation and rainfall. Copyright © 2006 Royal Meteorological Society [source]


Ecohydrological controls on snowmelt partitioning in mixed-conifer sub-alpine forests

ECOHYDROLOGY, Issue 2 2009
Noah P. Molotch
Abstract We used co-located observations of snow depth, soil temperature, and moisture and energy fluxes to monitor variability in snowmelt infiltration and vegetation water use at mixed-conifer sub-alpine forest sites in the Valles Caldera, New Mexico (3020 m) and on Niwot Ridge, Colorado (3050 m). At both sites, vegetation structure largely controlled the distribution of snow accumulation with 29% greater accumulation in open versus under-canopy locations. Snow ablation rates were diminished by 39% in under-canopy locations, indicating increases in vegetation density act to extend the duration of the snowmelt season. Similarly, differences in climate altered snow-season duration, snowmelt infiltration and evapotranspiration. Commencement of the growing season was coincident with melt-water input to the soil and lagged behind springtime increases in air temperature by 12 days on average, ranging from 2 to 33 days under warmer and colder conditions, respectively. Similarly, the timing of peak soil moisture was highly variable, lagging behind springtime increases in air temperature by 42 and 31 days on average at the Colorado and New Mexico sites, respectively. Latent heat flux and associated evaporative loss to the atmosphere was 28% greater for the year with earlier onset of snowmelt infiltration. Given the large and variable fraction of precipitation that was partitioned into water vapour loss, the combined effects of changes in vegetation structure, climate and associated changes to the timing and magnitude of snowmelt may have large effects on the partitioning of snowmelt into evapotranspiration, surface runoff and ground water recharge. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Soil microbial activity along an arctic-alpine altitudinal gradient from a seasonal perspective

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008
U. C. M. Löffler
Summary The knowledge on dynamics of soil microbial activity and its correlation to climate and vegetation is still poor but essential for predicting climatic changes scenarios. Seasonal dynamics of soil microbial activity and cell counts were studied along an arctic-alpine altitudinal gradient. The gradient comprised 12 ridges from 1000 to 1600 m altitude. Soil samples were collected during March, May, July and September 2005. The effect of temperature, snow depth and vegetation, all of which changed with altitude, on soil microbial activity and bacterial cell counts was analysed. The potential activities of phosphatase and chitinase were determined using fluorescent 4-methylumbelliferyl labelled analogues. Total and live bacterial cell counts were determined by live-dead-staining. We detected marked differences in soil microbial variables along the altitudinal gradient, forming three major clusters: a low alpine belt, a middle alpine belt, and an intermediate transition zone. Our results demonstrated that more frequent occurrence of shrubs and bryophytes would also increase microbial activity. Furthermore, we detected a clear relation (R2 = 0.6; P < 0.02) between high soil temperatures and greater soil microbial activity during summer. As higher temperatures are predicted to promote shrubs and higher humidity to promote bryophytes we expect microbial activity in dry heath tundra soils will increase with anticipated warmer, and in the case of Scandinavia, more humid climates. We did not find winter microbial activity to be less at snow-free sites than at sites covered by snow up to depths of 30 cm; hence, possible future decreases in snow depth will not result in reduced winter microbial activity. We demonstrate that shrubs support winter microbial activity not only by trapping snow but also directly by increasing the amount of organic carbon. [source]


Recent decay of a single palsa in relation to weather conditions between 1996 and 2000 in Laivadalen, northern Sweden

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2002
Frieda Sjoukje Zuidhoff
This study presents the decay of a small palsa complex between 1996 and 2000 in Sweden's southernmost major palsa bog. The outline of the palsa was mapped during three summers in 1996, 1999 and 2000 and an automatic weather station measured air temperature, precipitation, snow depth, wind speed and wind direction between 1997 and 2000. The decay of the palsa was enormous in the dome,shaped part of the palsa complex: the height decreased during the observation period from 2.3 m to 0.5 m. In 2000, the palsa dome had almost totally disappeared: only some peat blocks in a palsa pond were left. The decay of the palsa was complex with a number of degradational processes, of which the main processes were block erosion, thermokarst and wind erosion. Thermal melting has occurred along the edges of the palsa and possibly below the frozen core of the palsa since 1998/99. Wind erosion was observed during summer and the maximum estimated deflation was 80 cm. The decay of the palsa dome was especially large between 1999 and 2000, probably due to a high mean annual temperature, high summer precipitation and the warming influence of the large pond surrounding the palsa. The present climate in the palsa bog with a mean annual temperature of ,0.8°C is not favourable for palsa development and maintenance, despite a strong wind regime which can provide suitable conditions for snowdrift. [source]


The Ecological Role and Geography of Reindeer (Rangifer tarandus) in Northern Eurasia

GEOGRAPHY COMPASS (ELECTRONIC), Issue 4 2009
Bruce C. Forbes
The reindeer is a ruminant of the family Cervidae with a circumpolar distribution that has been a key component of Eurasian high latitude ecosystems for at least 2 million years. Interactions with humans date from the late Pleistocene onward and wild and semi-domestic animals continue to be highly valued by aboriginal and non-native peoples for a diversity of purposes. As a widespread and dominant ungulate across many tundra and taiga regions, the reindeer exerts a number of important controls on ecosystem structure and function. Animals, both free-ranging and herded, move seasonally between summer, winter and transitional spring/autumn habitats or ,pastures'. Their effects on vegetation and soils vary greatly in space and time depending on factors such as altitude/exposure, snow depth, substrate, moisture, prevailing vegetation type and, most importantly, animal density. At present, the number of Old World reindeer is somewhat less than 2.5 million. The most productive semi-domestic herds occur in Fennoscandia and the Nenets regions of northwest Russia straddling the Ural Mountains. Management systems differ within and among countries and regions. Given the diverse suite of factors involved, changes in vegetation associated with grazing and trampling can be remarkably heterogeneous spatially yet remain to a large extent predictable. Potential threats facing reindeer populations of Eurasia include rapid land use change, climate change and ongoing institutional conflicts. [source]


Modelled changes in arctic tundra snow, energy and moisture fluxes due to increased shrubs

GLOBAL CHANGE BIOLOGY, Issue 1 2002
Glen E. Liston
Abstract In arctic tundra, shrubs can significantly modify the distribution and physical characteristics of snow, influencing the exchanges of energy and moisture between terrestrial ecosystems and the atmosphere from winter into the growing season. These interactions were studied using a spatially distributed, physically based modelling system that represents key components of the land,atmosphere system. Simulations were run for 4 years, over a 4-km2 tundra domain located in arctic Alaska. A shrub increase was simulated by replacing the observed moist-tundra and wet-tundra vegetation classes with shrub-tundra; a procedure that modified 77% of the simulation domain. The remaining 23% of the domain, primarily ridge tops, was left as the observed dry-tundra vegetation class. The shrub enhancement increased the averaged snow depth of the domain by 14%, decreased blowing-snow sublimation fluxes by 68%, and increased the snowcover's thermal resistance by 15%. The shrub increase also caused significant changes in snow-depth distribution patterns; the shrub-enhanced areas had deeper snow, and the non-modified areas had less snow. This snow-distribution change influenced the timing and magnitude of all surface energy-balance components during snowmelt. The modified snow distributions also affected meltwater fluxes, leading to greater meltwater production late in the melt season. For a region with an annual snow-free period of approximately 90 days, the snow-covered period decreased by 11 days on the ridges and increased by 5 days in the shrub-enhanced areas. Arctic shrub increases impact the spatial coupling of climatically important snow, energy and moisture interactions by producing changes in both shrub-enhanced and non-modified areas. In addition, the temporal coupling of the climate system was modified when additional moisture held within the snowcover, because of less winter sublimation, was released as snowmelt in the spring. [source]


Effects of sample and grid size on the accuracy and stability of regression-based snow interpolation methods

HYDROLOGICAL PROCESSES, Issue 14 2010
J. Ignacio López Moreno
Abstract This work analyses the responses of four regression-based interpolation methods for predicting snowpack distribution to changes in the number of data points (sample size) and resolution of the employed digital elevation model (DEM). For this purpose, we used data obtained from intensive and random sampling of snow depth (991 measurements) in a small catchment (6 km2) in the Pyrenees, Spain. Linear regression, classification trees, generalized additive models (GAMs), and a recent method based on a correction made by applying tree classification to GAM residuals were used to calculate snow-depth distribution based on terrain characteristics under different combinations of sample size and DEM spatial resolution (grid size). The application of a tree classification to GAM residuals yielded the highest accuracy scores and the most stable models. The other tested methods yielded scores with slightly lower accuracy and varying levels of robustness under different conditions of grid and sample size. The accuracy of the model predictions declined with decreasing resolution of DEMs and sample size; however, the sensitivities of the models to the number of data points showed threshold values, which has implications (when planning fieldwork) for optimizing the relation between the effort expended in gathering data and the quality of the results. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Analysis of snow cover variability and change in Québec, 1948,2005

HYDROLOGICAL PROCESSES, Issue 14 2010
Ross D. Brown
Abstract The spatial and temporal characteristics of annual maximum snow water equivalent (SWEmax) and fall and spring snow cover duration (SCD) were analysed over Québec and adjacent area for snow seasons 1948/1949,2004/2005 using reconstructed daily snow depth and SWE. Snow cover variability in Québec was found to be significantly correlated with most of the major atmospheric circulation patterns affecting the climate of eastern North America but the influence was characterized by strong multidecadal-scale variability. The strongest and most consistent relationship was observed between the Pacific Decadal Oscillation (PDO) and fall SCD variability over western Québec. El Niño-Southern Oscillation (ENSO) was found to have a limited impact on Québec snow cover. Evidence was found for a shift in circulation over the study region around 1980 associated with an abrupt increase in sea level pressure (SLP) and decreases in winter precipitation, snow depth and SWE over much of southern Québec, as well as changes in the atmospheric patterns with significant links to snow cover variability. Trend analysis of the reconstructed snow cover over 1948,2005 provided evidence of a clear north,south gradient in SWEmax and spring SCD with significant local decreases over southern Québec and significant local increases over north-central Québec. The increase in SWEmax over northern Québec is consistent with proxy data (lake levels, tree growth forms, permafrost temperatures), with hemispheric-wide trends of increasing precipitation over higher latitudes, and with projections of global climate models (GCMs). Copyright © 2010 Her Majesty the Queen in right of Canada. Published by John Wiley & Sons. Ltd [source]


Assessing the effects of post-pine beetle forest litter on snow albedo

HYDROLOGICAL PROCESSES, Issue 6 2010
Rita Winkler
Abstract The effect of forest litter on snow surface albedo has been subject to limited study, mainly in the hardwood-dominated forests of the northeastern United States. Given the recent pine beetle infestation in Western North America and associated increases in litter production, this study examines the effects of forest litter on snow surface albedo in the coniferous forests of south-central British Columbia. Measured changes in canopy transmittance provide an indication of canopy loss or total litterfall over the winter of 2007,2008. Relationships between percent litter cover, an index of albedo, snow depth, and snow ablation during the 2008 melt season are compared between a mature, young, and clearcut coniferous stand. Results indicate a strong feedback effect between canopy loss and subsequent enhanced shortwave transmittance, and litter accumulation on the snow surface from that canopy loss. However, this relationship is confounded by other variables concurrently affecting albedo. While results suggest that a relatively small percent litter cover can have a significant effect on albedo and ablation, further research is underway to extract the litter signal from that of other factors affecting albedo, particularly snow depth. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Spatial patterns of simulated transpiration response to climate variability in a snow dominated mountain ecosystem

HYDROLOGICAL PROCESSES, Issue 18 2008
Lindsey Christensen
Abstract Transpiration is an important component of soil water storage and stream-flow and is linked with ecosystem productivity, species distribution, and ecosystem health. In mountain environments, complex topography creates heterogeneity in key controls on transpiration as well as logistical challenges for collecting representative measurements. In these settings, ecosystem models can be used to account for variation in space and time of the dominant controls on transpiration and provide estimates of transpiration patterns and their sensitivity to climate variability and change. The Regional Hydro-Ecological Simulation System (RHESSys) model was used to assess elevational differences in sensitivity of transpiration rates to the spatiotemporal variability of climate variables across the Upper Merced River watershed, Yosemite Valley, California, USA. At the basin scale, predicted annual transpiration was lowest in driest and wettest years, and greatest in moderate precipitation years (R2 = 0·32 and 0·29, based on polynomial regression of maximum snow depth and annual precipitation, respectively). At finer spatial scales, responsiveness of transpiration rates to climate differed along an elevational gradient. Low elevations (1200,1800 m) showed little interannual variation in transpiration due to topographically controlled high soil moistures along the river corridor. Annual conifer stand transpiration at intermediate elevations (1800,2150 m) responded more strongly to precipitation, resulting in a unimodal relationship between transpiration and precipitation where highest transpiration occurred during moderate precipitation levels, regardless of annual air temperatures. Higher elevations (2150,2600 m) maintained this trend, but air temperature sensitivities were greater. At these elevations, snowfall provides enough moisture for growth, and increased temperatures influenced transpiration. Transpiration at the highest elevations (2600,4000 m) showed strong sensitivity to air temperature, little sensitivity to precipitation. Model results suggest elevational differences in vegetation water use and sensitivity to climate were significant and will likely play a key role in controlling responses and vulnerability of Sierra Nevada ecosystems to climate change. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Snow density variations: consequences for ground-penetrating radar

HYDROLOGICAL PROCESSES, Issue 7 2006
A. Lundberg
Abstract Reliable hydrological forecasts of snowmelt runoff are of major importance for many areas. Ground-penetrating radar (GPR) measurements are used to assess snowpack water equivalent for planning of hydropower production in northern Sweden. The travel time of the radar pulse through the snow cover is recorded and converted to snow water equivalent (SWE) using a constant snowpack mean density from the drainage basin studied. In this paper we improve the method to estimate SWE by introducing a depth-dependent snowpack density. We used 6 years measurements of peak snow depth and snowpack mean density at 11 locations in the Swedish mountains. The original method systematically overestimates the SWE at shallow depths (+25% for 0·5 m) and underestimates the SWE at large depths (,35% for 2·0 m). A large improvement was obtained by introducing a depth,density relation based on average conditions for several years, whereas refining this by using separate relations for individual years yielded a smaller improvement. The SWE estimates were substantially improved for thick snow covers, reducing the average error from 162 ± 23 mm to 53 ± 10 mm for depth range 1·2,2·0 m. Consequently, the introduction of a depth-dependent snow density yields substantial improvements of the accuracy in SWE values calculated from GPR data. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Karakorum,Hindukush,western Himalaya: assessing high-altitude water resources

HYDROLOGICAL PROCESSES, Issue 12 2005
M. Winiger
Abstract The high mountains of Central and South Asia provide irrigation water for their adjacent lowlands. The Indus Irrigation Scheme depends on approximately 50% of its runoff originating from snowmelt and glacier melt from the eastern Hindukush, Karakorum and western Himalaya. The Atlas of Pakistan indicates that these mountains gain a total annual rainfall of between 200 and 500 mm, amounts that are generally derived from valley-based stations and not representative for elevated zones. High-altitude snowfall seems to be neglected and is obviously still rather unknown. Estimates derived from accumulation pits runoff above 4000 m range from 1000 mm to more than 3000 mm, depending on the site and time of investigation, as well as on the method applied. To assess the vertical spatio-temporal distribution of total annual precipitation, a combined approach is presented. This approach links in situ measurements of snow depth and water equivalent (10-year time series derived from automatic weather stations at elevations between 1500 and 4700 m a.s.l.), the spatial distribution and period of snow coverage (remotely sensed data and digital elevation models), and the runoff characteristics of streams originating from snow or snow/ice-covered watersheds (modified snowmelt runoff model, including intermediate snowfall and glacier runoff). Based on conservative assumptions, the vertically changing seasonal ratio between liquid and solid precipitation is calculated. Using a combined snow cover and ablation model, total annual amounts of precipitation are derived for different altitudinal zones. Amounts of modelled and measured runoff complement the investigation. Horizontal gradients along the Indus,Gilgit,Hunza transect indicate the varying dominance of seasonal precipitation regimes (monsoonal, Mediterranean and continental disturbances) south of Nanga Parbat, between Nanga Parbat and Batura Wall (=West Karakorum rainfall regime: 1500,1800 mm year,1 at 5000 m) and areas north of Batura (=Central Asian rainfall regime: ,600 mm year,1 at 5000 m). Copyright © 2005 John Wiley & Sons, Ltd. [source]


Statistical probability distribution of snow depth at the model sub-grid cell spatial scale

HYDROLOGICAL PROCESSES, Issue 2 2005
Dr Wolf-Dietrich Marchand
Abstract Comprehensive snow depth data, collected using georadar and hand probing, were used for statistical analyses of snow depths inside 1 km grid cells. The sub-grid cell spatial scale was 100 m. Statistical distribution functions were found to have varying parameters, and an attempt was made to connect these statistical parameters to different terrain variables. The results showed that the two parameters mean and standard deviation of snow depth were significantly related to the sub-grid terrain characteristics. Linear regression models could explain up to 50% of the variation for both of the snowcover parameters mentioned. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Evaluation of spatial variability in snow water equivalent for a high mountain catchment

HYDROLOGICAL PROCESSES, Issue 3 2004
S. P. Anderton
Abstract Multivariate statistical analysis was used to explore relationships between catchment topography and spatial variability in snow accumulation and melt processes in a small headwater catchment in the Spanish Pyrenees. Manual surveys of snow depth and density provided information on the spatial distribution of snow water equivalent (SWE) and its depletion over the course of the 1997 and 1998 melt seasons. A number of indices expressing the topographic control on snow processes were extracted from a detailed digital elevation model of the catchment. Bivariate screening was used to assess the relative importance of these topographic indices in controlling snow accumulation at the start of the melt season, average melt rates and the timing of snow disappearance. This suggested that topographic controls on the redistribution of snow by wind are the most important influence on snow distribution at the start of the melt season. Furthermore, it appeared that spatial patterns of snow disappearance were largely determined by the distribution of snow water equivalent (SWE) at the start of the melt season, rather than by spatial variability in melt rates during the melt season. Binary regression tree models relating snow depth and disappearance date to terrain indices were then constructed. These explained 70,80% of the variance in the observed data. As well as providing insights into the influence of topography on snow processes, it is suggested that the techniques presented herein could be used in the parameterization of distributed snowmelt models, or in the design of efficient stratified snow surveys. Copyright © 2003 John Wiley & Sons, Ltd. [source]


The simulation of heat and water exchange at the land,atmosphere interface for the boreal grassland by the land-surface model SWAP

HYDROLOGICAL PROCESSES, Issue 10 2002
Yeugeniy M. Gusev
Abstract The major goal of this paper is to evaluate the ability of the physically based land surface model SWAP to reproduce heat and water exchange processes that occur in mid-latitude boreal grassland regions characterized by a clear seasonal course of hydrometeorological conditions, deep snow cover, seasonally frozen soil, as well as seasonally mobile and shallow water table depth. A unique set of hydrometeorological data measured over 18 years (1966,83) at the Usadievskiy catchment (grassland) situated in the central part of Valdai Hills (Russia) provides an opportunity to validate the model. To perform such validation in a proper way, SWAP is modified to take into account a shallow water table depth. The new model differs from its previous version mainly in the parameterization of water transfer in a soil column; besides that, it includes soil water,groundwater interaction. A brief description of the new version of SWAP and the results of its validation are presented. Simulations of snow density, snow depth, snow water equivalent, daily snow surface temperature, daily evaporation from snow cover, water yield of snow cover, water table depth, depth of soil freezing and thawing, soil water storage in two layers, daily surface and total runoff from the catchment, and monthly evaporation from the catchment are validated against observations on a long-term basis. The root-mean-square errors (RMSEs) of simulations of soil water storage in the layers of 0,50 cm and 0,100 cm are equal to 16 mm and 24 mm respectively; the relative RMSE of simulated annual total runoff is 16%; the RMSE of daily snow surface temperature is 2·9 °C (the temperature varies from 0 to ,46 °C); the RMSE of maximum snow water equivalent (whose value averaged over 18 years is equal to 147 mm) is 32 mm. Analysis of the results of validation shows that the new version of the model SWAP reproduces the heat and water exchange processes occurring in mid-latitude boreal grassland reasonably well. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Soil frost effects on soil water and runoff dynamics along a boreal forest transect: 1.

HYDROLOGICAL PROCESSES, Issue 6 2001
Field investigations
Abstract To determine how soil frost changes flowpaths of runoff water along a hillslope, a transect consisting of four soil profiles directed towards a small stream in a mature forest stand was investigated at Svartberget, near Vindeln in northern Sweden. Soil temperature, unfrozen water content, groundwater level and snow depth were investigated along the transect, which started at the riparian peat, and extended 30 m upslope into mineral soils. The two, more organic-rich profiles closest to the stream had higher water retention and wetter autumn conditions than the sandy mineral soils further upslope. The organic content of the soil influenced the variation in frost along the transect. The first winter (1995,96) had abnormally low snow precipitation, which gave a deep frost down to 40,80 cm, whereas the two following winters had frost depths of 5,20 cm. During winter 1995,96, the two organic profiles close to the stream had a shallower frost depth than the mineral soil profile higher upslope, but a considerably larger amount of frozen water. The fraction of water that did not freeze despite several minus degrees in the soil was 5,7 vol.% in the mineral soil and 10,15 vol.% in the organic soil. From the measurements there were no signs of perched water tables during any of the three snowmelt periods, which would have been strong evidence for changed water flowpaths due to soil frost. When shallow soil layers became saturated during snowmelt, especially in 1997 and 1998, it was because of rising groundwater levels. Several rain on frozen ground events during spring 1996 resulted in little runoff, since most of the rain either froze in the soil or filled up the soil water storage. Copyright © 2001 John Wiley & Sons, Ltd. [source]


A study on the effect of Eurasian snow on the summer monsoon circulation and rainfall using a spectral GCM

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2006
S. K. Dash
Abstract Many studies based on observed data indicate the inverse relationship between the Eurasian snow cover/depth and the Indian summer monsoon rainfall (ISMR). The purpose of this study is to confirm the inverse snow,ISMR relationship by using the observed snow depth data as boundary conditions in the spectral general circulation model (GCM) of Indian Institute of Technology, Delhi (IITD), and to examine the influence of Eurasian snow depth on the monsoon circulation. The original model belonging to the European Centre for Medium range Weather Forecasts (ECMWF) at resolution T21 has been modified extensively to a higher resolution of T80L18 at IITD. A two-dimensional Lanczos digital filter has been used to represent the orography realistically. The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used for conducting sensitivity experiments using the above model. Two sensitivity experiments have been designed, corresponding to two contrasting cases: one with high Eurasian snow depth in spring followed by deficient ISMR and the second with low snow depth followed by excess ISMR. The difference fields of mean monsoon circulation simulated in the above two experiments are examined in detail in order to confirm the influence of Eurasian snow depth on ISMR and to examine the Asian summer monsoon circulation and rainfall. Copyright © 2006 Royal Meteorological Society [source]


Responses of China's summer monsoon climate to snow anomaly over the Tibetan Plateau

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2003
Prof. Y. F. Qian
Abstract The climatological features of the winter snow depth over the Tibetan Plateau and the summer precipitation in China are diagnosed using datasets obtained from 78 snow observation stations and 160 rainfall stations during 1957 to 1998. The climatic effects of the snow anomaly over the Tibetan Plateau on the regional summer monsoon climate in China are diagnosed and numerically simulated by use of a regional climate model (RegCM2). The singular value decomposition technique is adopted to diagnose the relationships between the previous winter and spring plateau snow depth anomalies and the spring and summer regional precipitation in China. It is found that the snow depth anomaly, especially in winter, is one of the factors influencing precipitation in China; however, it is perhaps not the only one, and even not the most important one. Nevertheless, it is proved that the winter snow anomaly over the Tibetan Plateau is relatively more important than that in spring for the regional precipitation in China. Results of numerical simulations show that the snow anomaly over the plateau has effects that are evident on China's summer monsoon climate. The increase of both snow cover and snow depth can delay the onset and weaken the intensity of the summer monsoon obviously, resulting in a decrease in precipitation in southern China and an increase in the Yangtze and Huaihe River basins. The influence of the winter snow depth is more substantial than that of both the winter snow cover and the spring snow depth. The mechanism of how the plateau snow anomaly influences the regional monsoon climate is briefly analysed. It is found that snow anomalies over the Tibetan Plateau change the soil moisture and the surface temperature through the snowmelt process at first, and subsequently alter heat, moisture and radiation fluxes from the surface to the atmosphere. Abnormal circulation conditions induced by changes of surface fluxes may affect the underlying surface properties in turn. Such a long-term interaction between the wetland and the atmosphere is the key process resulting in later climatic changes. Copyright © 2003 Royal Meteorological Society [source]


Lagged teleconnections between snow depth in northern Eurasia, rainfall in Southeast Asia and sea-surface temperatures over the tropical Pacific Ocean

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2001
Hengchun Ye
Abstract This study shows that above-(below-)normal winter snow depth over European Russia and corresponding below-(above-)normal snow depth over central Siberia is associated with reduced (increased) summer monsoon rainfall over southern and western India and eastern Pakistan, and above-(below-)normal sea-surface temperatures (SSTs) over the eastern and central tropical Pacific Ocean during the following winters. The connection is slightly stronger when snow depth over European Russia is above normal than below normal. These results are derived from an examination of 60 years (1936,1995) of winter snow depth data and SSTs, and 45 years (1951,1995) of summer precipitation records. The results of this study suggest that winter snow depth over the western rather than the eastern portion of Eurasia is critical to Southeast Asian summer monsoon rainfall and eastern tropical Pacific SSTs during the following seasons. Copyright © 2001 Royal Meteorological Society [source]


Overwinter mass loss of snowshoe hares in the Yukon: starvation, stress, adaptation or artefact?

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2006
KAREN E. HODGES
Summary 1Overwinter mass loss can reduce energetic requirements in mammals (Dehnel's phenomenon). Alternatively, mass loss can result from food limitation or high predation risk. 2We use data from fertilizer, food-supplementation and predator-exclusion experiments in the Yukon during a population cycle from 1986 to 1996 to test the causes of overwinter mass loss by snowshoe hares (Lepus americanus). In all years, some hares on control sites gained mass overwinter. During the increase phase the majority gained mass, but in all other phases the majority lost mass. 3Snowshoe hares weighing < 1000 g in autumn always gained mass overwinter, as did the majority that weighed 1000,1400 g. Hares weighing > 1800 g in autumn usually lost mass. 4Snowshoe hares on the predator-exclosure + food site gained mass overwinter in all years. Hares on the food-supplementation sites lost mass during the decline but gained mass in all other phases. Fertilization had little effect on mass dynamics. 5Snowshoe hares were more likely to lose mass during winters with low survival rates. Snowshoe hares on the predator-exclosure treatments were more likely to gain mass than were hares on control sites. 6Overwinter mass loss was correlated with maximum snow depth. At equivalent snow depths, hares on food-supplemented areas lost 98 g (± 14·6 SE) less on average than hares on the controls and predator-exclosure treatment. 7Bone-marrow fat was related to body mass and cause of death. Small hares had the lowest marrow fat. Hares killed by humans had higher marrow fat than those killed by predators; hares that simply died had the lowest marrow fat. Hares on food-supplemented sites had the highest kidney and marrow fat. 8Overwinter-mass loss for snowshoe hares is explained interactively by winter conditions, food supply, predation risk and autumn mass. Some snowshoe hares lost mass overwinter in all years and on all treatments, suggesting that reducing body mass may facilitate survival, especially in cases where foraging costs are high energetically or increase predation risk. [source]


Abrupt increases in soil temperatures following increased precipitation in a permafrost region, central Lena River basin, Russia

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2010
Yoshihiro Iijima
Abstract Marked increases in active-layer and upper permafrost temperatures occurred in the central Lena River basin in association with abrupt increases in active-layer soil moisture following the summer of 2005. The positive trend in soil temperature-moisture relations was observed at monitoring sites in the Yakutsk area, regardless of vegetation and soil type. The increase in soil temperature appears to have started in response to the large amounts of snow that accumulated in the winter of 2004. Abnormally high pre-winter rainfall and snowfall in the following three years accelerated soil warming through the effects of greater latent heat of freezing and insulation from atmospheric cooling in winter. The consecutive positive anomalies of snow depth and rainfall, which occurred widely in the central and southern Lena River basin during this three-year period, increased soil moisture and appear to have altered the active-layer thermal properties, which likely induced widespread warming of the surface layer of permafrost in this region. Copyright © 2009 John Wiley & Sons, Ltd. [source]


The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, Russia

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009
Valeria V. Popova
Abstract Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analysed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1,2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5,10,m depth were correlated with spring air temperatures in the current and preceding 1,2 years. The weather regime during the preceding 1,2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasising the importance of analyses at short temporal scales and for individual terrain units. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Thawing permafrost and thicker active layers in sub-arctic Sweden

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2008
H. Jonas Åkerman
Abstract Observations of active-layer thickness from nine sites with up to 29 years of gridded measurements located in the Torneträsk region, northernmost Sweden, were examined in relation to climatic trends. Mean annual air temperatures in this area have warmed and recently rose above 0°C. Active layers at all sites have become thicker, at rates ranging from 0.7 to 1.3,cm per year. This trend has accelerated in the past decade, especially in the westernmost site where rates have reached 2,cm per year and permafrost has disappeared at 81 per cent of the sampling points. Increased active-layer thicknesses are correlated with increases in mean summer air temperature, thawing degree-days and, in five of the nine sites, with increases in snow depth. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Frost boils and soil ice content: field observations

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2006
P. P. Overduin
Abstract Our aim is to measure and explain the seasonal changes in soil ice content in the frost boils of Galbraith Lake, Alaska. Instruments were installed in a frost boil to monitor the ground surface position and soil state over a period of 4 years. By comparing the subsidence and thaw rates, we calculate the soil ice content as a function of depth. Measured soil temperatures, liquid water contents and bulk apparent thermal conductivities are used to estimate latent heat production and release in the soil. The frost boil heaves during freezing and settles during thaw while the surrounding tundra heaves negligibly, but subsides measurably. Despite large changes in freezing rates from year to year, total heave and its distribution across the frost boil are similar between years. Winter air temperature and snow depth influence the freezing rate and ice distribution as a function of depth, but not the overall heave. This suggests that heave is controlled by water availability rather than the rate of heat removal from the soil. Areal ground subsidence rates between 2 and 5,cm/yr are due to the disappearance of ice at the base of the active layer, raising the possibility of ongoing thermokarst expansion around Galbraith Lake. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Needle traits of an evergreen, coniferous shrub growing at wind-exposed and protected sites in a mountain region: does Pinus pumila produce needles with greater mass per area under wind-stress conditions?

PLANT BIOLOGY, Issue 2009
S. Nagano
Abstract Snow depth is one of the most important determinants of vegetation, especially in mountainous regions. In such regions, snow depth tends to be low at wind-exposed sites such as ridges, where stand height and productivity are limited by stressful environmental conditions during winter. Siberian dwarf pine (Pinus pumila Regel) is a dominant species in mountainous regions of Japan. We hypothesized that P. pumila produces needles with greater mass per area at wind-exposed sites than at wind-protected sites because it invests more nitrogen (N) in cell walls at the expense of N investment in the photosynthetic apparatus, resulting in increased photosynthetic N use efficiency (PNUE). Contrary to our hypothesis, plants at wind-exposed site invested less resources in needles, as exhibited by lower biomass, N, Rubisco and cell wall mass per unit area, and had higher photosynthetic capacity, higher PNUE and shorter needle life-span than plants at a wind-protected site. N partitioning was not significantly different between sites. These results suggest that P. pumila at wind-exposed sites produces needles at low cost with high productivity to compensate for a short leaf life-span, which may be imposed by wind stress when needles appear above the snow surface in winter. [source]


Statistical probability distribution of snow depth at the model sub-grid cell spatial scale

HYDROLOGICAL PROCESSES, Issue 2 2005
Dr Wolf-Dietrich Marchand
Abstract Comprehensive snow depth data, collected using georadar and hand probing, were used for statistical analyses of snow depths inside 1 km grid cells. The sub-grid cell spatial scale was 100 m. Statistical distribution functions were found to have varying parameters, and an attempt was made to connect these statistical parameters to different terrain variables. The results showed that the two parameters mean and standard deviation of snow depth were significantly related to the sub-grid terrain characteristics. Linear regression models could explain up to 50% of the variation for both of the snowcover parameters mentioned. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Sensitivity analysis of snow patterns in Swiss ski resorts to shifts in temperature, precipitation and humidity under conditions of climate change

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2009
Bastienne Uhlmann
Abstract The value of snow as a resource has considerably increased in Swiss mountain regions, in particular in the context of winter tourism. In the perspective of a warming climate, it is thus important to quantify the potential changes in snow amount and duration that could have large repercussions on the economy of ski resorts. Because of the fine spatial variability of snow, the use of a Surface Energy Balance Model (SEBM) is adequate to simulate local snow cover evolution. A perturbation method has been developed to generate plausible future meteorological input data required for SEBM simulations in order to assess the changes in snow cover patterns. Current and future snow depths have also been simulated within the ski areas themselves. The results show a large decrease of the snow depths and duration, even at high elevation in a warmer climate and emphasize the sensitivity of snow to topographical characteristics of the resorts. The most vulnerable areas would be the Western regions of Switzerland or the Eastern Prealps whereas the Central Alps or Valais would be less affected. The study highlights the fact that not only the altitude of a domain but also its exposure, localization inland and slope gradients need to be taken into account when evaluating current and future snow depths. This method enables a precise assessment of the snow pattern over a small area. Copyright © 2008 Royal Meteorological Society [source]


Overwinter mass loss of snowshoe hares in the Yukon: starvation, stress, adaptation or artefact?

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2006
KAREN E. HODGES
Summary 1Overwinter mass loss can reduce energetic requirements in mammals (Dehnel's phenomenon). Alternatively, mass loss can result from food limitation or high predation risk. 2We use data from fertilizer, food-supplementation and predator-exclusion experiments in the Yukon during a population cycle from 1986 to 1996 to test the causes of overwinter mass loss by snowshoe hares (Lepus americanus). In all years, some hares on control sites gained mass overwinter. During the increase phase the majority gained mass, but in all other phases the majority lost mass. 3Snowshoe hares weighing < 1000 g in autumn always gained mass overwinter, as did the majority that weighed 1000,1400 g. Hares weighing > 1800 g in autumn usually lost mass. 4Snowshoe hares on the predator-exclosure + food site gained mass overwinter in all years. Hares on the food-supplementation sites lost mass during the decline but gained mass in all other phases. Fertilization had little effect on mass dynamics. 5Snowshoe hares were more likely to lose mass during winters with low survival rates. Snowshoe hares on the predator-exclosure treatments were more likely to gain mass than were hares on control sites. 6Overwinter mass loss was correlated with maximum snow depth. At equivalent snow depths, hares on food-supplemented areas lost 98 g (± 14·6 SE) less on average than hares on the controls and predator-exclosure treatment. 7Bone-marrow fat was related to body mass and cause of death. Small hares had the lowest marrow fat. Hares killed by humans had higher marrow fat than those killed by predators; hares that simply died had the lowest marrow fat. Hares on food-supplemented sites had the highest kidney and marrow fat. 8Overwinter-mass loss for snowshoe hares is explained interactively by winter conditions, food supply, predation risk and autumn mass. Some snowshoe hares lost mass overwinter in all years and on all treatments, suggesting that reducing body mass may facilitate survival, especially in cases where foraging costs are high energetically or increase predation risk. [source]


The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, Russia

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009
Valeria V. Popova
Abstract Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analysed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1,2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5,10,m depth were correlated with spring air temperatures in the current and preceding 1,2 years. The weather regime during the preceding 1,2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasising the importance of analyses at short temporal scales and for individual terrain units. Copyright © 2009 John Wiley & Sons, Ltd. [source]