scholarly journals Snowmelt lysimeters in the evaluation of snowmelt models

2000 ◽  
Vol 31 ◽  
pp. 405-410 ◽  
Author(s):  
Richard Kattelmann
Keyword(s):  
Sierra Nevada ◽  
Basic Problem ◽  
Unit Area ◽  
Water Flux ◽  
Great Variability ◽  
Lateral Flow ◽  
Snow Surface ◽  
Physical Measurement ◽  
Area Basis ◽  
The Mean

AbstractSnowmelt lysimeters have been used occasionally to provide a physical measurement for testing models of snowpack energy balance and/or meltwater production. Despite the attractiveness of using records of snowpack outflow for comparison with model results, there are many difficulties with using such data for this purpose. The basic problem is poor correspondence between melt produced at the snow surface and water arriving at the base of the snowpack on a unit-area basis. Unenclosed snowmelt lysimeters allow lateral flow of water into and out of the column of snow overlying the collector. The well-known lateral flow of water in a snowpack allows the effective contributing area at the snowpack surface to be different from the surface area of the collector. Data from several years at two research stations in the Sierra Nevada, California, U.S.A., illustrate the great variability of water flux measured by several collectors. However, the mean of accumulated outflow for a melt season from all the collectors tended to be close to the water equivalence of the overlying snowpack at the onset of snowmelt. Therefore, there is some hope that a set of small snowmelt lysimeters or a few large collectors can adequately sample outflow from the base of the snowpack.

scholarly journals Evaporation from Snow in the Central Sierra Nevada of California

1999 ◽  
Vol 30 (2) ◽  
pp. 81-108 ◽  
Author(s):  
Al Leydecker ◽  
John M. Melack
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Sierra Nevada ◽  
Meteorological Data ◽  
Snow Surface ◽  
Maximum Accumulation ◽  
Annual Evaporation ◽  
Evaporative Loss ◽  
The Mean ◽  
Vapor Pressure Gradient

Evaporation from snow was calculated with the mean-profile method using single-level meteorological data at eight locations representing a variety of alpine and sub-alpine terrain in the central Sierra Nevada, California. Four to six years of data were analyzed at most of the sites. Evaporation from snow was highest in mid-winter, when the vapor pressure gradient between the snow surface and the air was at its maximum, and declined throughout the snowmelt season. Near the end of snowmelt, condensation of water vapor on the snow surface often matched or exceeded evaporative loss. Annual evaporation from the snowpack varied from 12 to 156 mm. We estimate mean annual regional evaporation in the sub-alpine and alpine zones (excluding evaporation from tree-captured snow and during wind re-deposition) as 80 to 100 mm, approximately 7 per cent of the maximum accumulation during an average snow year. Evaporation during snowmelt contributed only minor amounts to the total seasonal loss, typically around 25 mm, or about 2% of the maximum average accumulation.

scholarly journals Cambial Activity and Phenology in Three Understory Species along an Altitude Gradient in Mexico

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 506
Author(s):  
Mayte S. Jiménez-Noriega ◽  
Lauro López-Mata ◽  
Teresa Terrazas
Keyword(s):  
Soil Temperature ◽  
Sierra Nevada ◽  
Cambial Activity ◽  
Life Forms ◽  
Dry Season ◽  
Vascular Cambium ◽  
Phenological Stages ◽  
Altitude Gradient ◽  
The Mean ◽  
Trees And Shrubs

The aims of this study were to evaluate the cambial activity and phenology of three species with different life forms (Alchemilla procumbens, Acaena elongata and Ribes ciliatum) along an altitudinal gradient and to establish which environmental variables (light, soil humidity and temperature) had the greatest influence on cambial activity and phenological stages. Over two years, data on phenology, growth and cambium were gathered every four weeks in three to six sites per species in Sierra Nevada, Mexico. The results showed that Ribes is the only species that terminates cambial activity with leaves senescence and is influenced by the minimum soil temperature. The light environment influenced the vegetative stages in Alchemilla (cryptophyte), while in Acaena (hemicryptophyte), the mean soil temperature explained the findings related to leaf area during the dry season and growth along the gradient. In the three species, the reproductive phase dominated for a longer period at higher elevations, especially in Alchemilla. Only Ribes, the phanerophyte, showed a similar cambial activity to other trees and shrubs. Although cambium reactivates during the dry season, no xylogenesis occurs. The three species varied during the time in which vascular cambium was active, and this was dependent on the altitude. Specifically, the variation was more rhythmic in Ribes and switched on and off in Alchemilla. It is likely that, depending on the life form, vascular cambium may be more or less susceptible to one or more climate factors.

scholarly journals Energy expenditure of free-living reindeer estimated by the doubly labelled water method

Rangifer ◽  
2000 ◽  
Vol 20 (2-3) ◽  
pp. 211 ◽  
Author(s):  
Geir Gotaas ◽  
Eric Milne ◽  
Paul Haggarty ◽  
Nicholas J.C. Tyler
Keyword(s):  
Energy Expenditure ◽  
Rangifer Tarandus ◽  
Water Flux ◽  
Co2 Production ◽  
Wild Ungulates ◽  
Free Living ◽  
Doubly Labelled Water ◽  
Svalbard Reindeer ◽  
Mountain Pasture ◽  
The Mean

The doubly labelled water (DLW) method was used to measure total energy expenditure (TEE) in three male reindeer (Rangifer tarandus tarandus) aged 22 months in winter (February) while the animals were living unrestricted at natural mountain pasture in northern Norway (69°20'N). The concentrations of 2H and l8O were measured in water extracted from samples of faeces collecred from the animals 0.4 and 11.2 days after injection of the isotopes. Calculated rates of water flux and CO2-production were adjusted to compensate for estimated losses of 2H in faecal solids and in methane produced by microbial fermentation of forage in the rumen. The mean specific TEE in the three animals was 3.057 W.kg-1 (range 2.436 - 3.728 W.kg1). This value is 64% higher than TEE measured by the DLW method in four captive, non-pregnant adult female reindeer in winter and probably mainly reflects higher levels of locomotor activity in the free-living animals. Previous estimates of TEE in free-living Rangifer in winter based on factorial models range from 3.038 W.kg-1 in female woodland caribou (R. t. caribou) to 1.813 W.kg-1 in female Svalbard reindeer (R. t. platyrhynchus). Thus, it seems that existing factorial models are unlikely to overestimate TEE in reindeer/caribou: they may, instead, be unduly conservative. While the present study serves as a general validation of the factorial approach, we suggest that the route to progress in the understanding of field energetics in wild ungulates is via application of the DLW method.

scholarly journals The Formation of Drainage Wind on a Snow-Dome

1965 ◽  
Vol 5 (42) ◽  
pp. 833-841 ◽  
Author(s):  
J.A. Businger ◽  
K. Ramana Rao
Keyword(s):  
Heat Flux ◽  
Temperature Profile ◽  
Energy Budget ◽  
Air Flow ◽  
Sensible Heat Flux ◽  
Wind Component ◽  
Sensible Heat ◽  
Snow Surface ◽  
Direct Measurements ◽  
The Mean

Abstract Direct measurements of the horizontal divergence of the air flow close to the snow surface have been made. The mean vertical wind component has been derived from these observations. The temperature profile has been analyzed near the center of the snow-dome and a method to determine the sensible heat flux independent from the energy budget has been developed.

scholarly journals Observations of snowpack ripening in the Sierra Nevada, California, U.S.A.

1999 ◽  
Vol 45 (151) ◽  
pp. 409-416 ◽  
Author(s):  
Richard Kattelmann ◽  
Jeff Dozier
Keyword(s):  
Snow Cover ◽  
Latent Heat ◽  
Sierra Nevada ◽  
Ice Sheets ◽  
Snow Surface ◽  
Layer Development

AbstractThe transition from a dry, sub-freezing snow cover to isothermal snow freely conducting water was observed near timberline in the Sierra Nevada, California, U.S.A. Although there were few major stratigraphic boundaries in the snowpacks observed, minor textural discontinuities were sufficient to both route water laterally downslope and later create ice layers at these strata. During the first few days of snowmelt, downslope movement of water parallel to the strata allowed water to bypass lower layers of the snow cover on slopes and converge in microtopographic depressions on level terrain, creating isolated drains through the snowpack. In addition to these drains, flow fingers associated with holes in the ice sheets delivered water to the base of the snow several days prior to the thorough wetting of the snowpack. Formation of a series of ice lenses just below the snow surface every night released much more latent heat than did ice-layer development within the bulk of the snowpack or at its base.

A Rational Approach to the Mapping of Freeze Dates1,2

1961 ◽  
Vol 42 (10) ◽  
pp. 703-714 ◽  
Author(s):  
Joseph M. Caprio
Keyword(s):  
Diurnal Temperature Range ◽  
Unit Area ◽  
Rational Approach ◽  
Maximum Temperature ◽  
Statistical Relation ◽  
Night Time ◽  
Interval Maps ◽  
Diurnal Temperature ◽  
Close Proximity ◽  
The Mean

Two methods of estimating average last-freeze dates as applied in Montana are described. Both methods are based on the observation that day-time-temperature differences between Weather Bureau climatological stations in close proximity and at the same elevation are much less than night-time differences in temperature. A procedure for drawing 100-ft-elevation-interval maps of the date when the mean maximum temperature reaches 70F in the spring is described. The first method of estimating freeze dates is based on the statistical relation between average date of last spring freeze, the date when the mean maximum temperature reaches 70F and average diurnal temperature range at the time. The second method incorporates the same general parameters but is based entirely on mapping procedures. A method of mapping average last-freeze dates is described employing the unit area concept, which can be applied in connection with either method of estimating average last-freeze dates.

Seasonal Field Energetics of the Rufous Rat-Kangaroo (Aepyprymnus-Rufescens)

1992 ◽  
Vol 40 (3) ◽  
pp. 279 ◽  
Author(s):  
IR Wallis ◽  
B Green
Keyword(s):  
New South ◽  
Water Flux ◽  
Behavioural Ecology ◽  
Free Living ◽  
Doubly Labelled Water ◽  
South Wales ◽  
Poor Understanding ◽  
Males And Females ◽  
The Mean ◽  
The Difference

Water flux and field metabolic rate (FMR) were measured by the doubly labelled water (DLW) method in free-living male and female rufous rat-kangaroos Aepyprymnus rufescens near Drake in northern New South Wales. The mean FMR of 499 kJ kg-1 day-1 was similar in winter and summer even though the difference in mean minimum temperatures between the two seasons was 20-degrees-C. Furthermore, we did not find any differences in FMR between males and females even though several females carried large pouch young or had young-at-foot. A poor understanding of the diet and the behavioural ecology of A. rufescens makes ft difficult to explain the similarities between sexes and seasons.

Theory of the Non-Newtonian Rheology of Raw Rubbers Consisting of Supermolecular Rheological Units

1957 ◽  
Vol 30 (2) ◽  
pp. 460-469 ◽  
Author(s):  
M. Mooney
Keyword(s):  
Experimental Data ◽  
Flow Curve ◽  
Unit Area ◽  
Mathematical Treatment ◽  
Relative Movement ◽  
Elastic Solids ◽  
Continuous Shear ◽  
The Mean ◽  
Better Than

Abstract A theory of the viscosity of raw rubbers is developed on the postulate that raw rubbers, when subjected to continuous shear in the non-Newtonian region of flow, consist of microscopic rheological units which are semipermanent aggregates of many rubber molecules. The theory treats these units as tacky, elastic solids, whose relative movement and slippage constitute the macroscopic flow of the rubber. The resulting theoretical flow curve differs little from that given by Smallwood, but the interpretation of the parameters is radically different. The new theory leads to expressions for the number of temporary point attachments per unit area between two touching rheological units and for the mean life of these attachments. Agreement with experimental data is slightly better than in Smallwood. Two types of observed deviation from the theory can be interpreted as due to two plausible phenomena not included in the mathematical treatment.

scholarly journals Elemental carbon in snow at Changbai Mountain, northeastern China: concentrations, scavenging ratios, and dry deposition velocities

2014 ◽  
Vol 14 (2) ◽  
pp. 629-640 ◽  
Author(s):  
Z. W. Wang ◽  
J. C. Gallet ◽  
C. A. Pedersen ◽  
X. S. Zhang ◽  
J. Ström ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Radiative Forcing ◽  
Elemental Carbon ◽  
Northeastern China ◽  
Snow Surface ◽  
Deposition Fluxes ◽  
The Mean ◽  
Deposition Processes ◽  
Scavenging Ratio

Abstract. Light-absorbing aerosol – particularly elemental carbon (EC) – while mixed with snow and ice is an important climate driver from the enhanced absorption of solar radiation. Currently, considerable efforts are being made to estimate its radiative forcing on a global scale, but several uncertainties remain, particularly those regarding its deposition processes. In this study, concurrent measurements of EC in air and snow are performed for three years (2009–2012) at Changbai station, northeastern China. The scavenging ratio and the wet- and dry-deposition fluxes of EC over the snow surface are estimated. The mean EC concentration in the surface snow is 1000 ± 1500 ng g−1, ranging from 7 to 7640 ng g−1. The mean value of the scavenging ratio of EC by snow is 140 ± 100, with a median value of 150, which is smaller than that reported in Arctic areas. A non-rimed snow process is a significant factor in interpreting differences with Arctic areas. Wet-deposition fluxes of EC are estimated to be 0.47 ± 0.37 μg cm−2 month−1 on average over the three snow seasons studied. Dry deposition is more than five times higher, with an average of 2.65 ± 1.93 μg cm−2 month−1; however, only winter period estimation is possible (December–February). During winter in Changbai, 87% of EC in snow is estimated to be due to dry deposition, with a mean dry deposition velocity of 6.44 × 10−3 m s−1 and median of 8.14 × 10−3 m s−1. Finally, the calculation of the radiative effect shows that 500 ng g−1 of dry-deposited EC to a snow surface absorbs three times more incoming solar energy than the same mass mixed in the snow through wet deposition. Deposition processes of an EC-containing snow surface are, therefore, crucial to estimate its radiative forcing better, particularly in northeastern China, where local emission strongly influences the level and gradient of EC in the snowpack, and snow-covered areas are cold and dry due to the atmospheric general circulation. Furthermore, this study builds on the knowledge to characterize the conditions in the snow-laden Chinese rural areas better as well as to constrain transport of EC to the Arctic better.

The fleece of the Scottish Blackface sheep I. Seasonal changes in wool production and fleece structure

1961 ◽  
Vol 56 (3) ◽  
pp. 365-374 ◽  
Author(s):  
J. M. Doney ◽  
W. F. Smith
Keyword(s):  
Fibre Type ◽  
Seasonal Changes ◽  
Unit Area ◽  
Late Pregnancy ◽  
Area Ratio ◽  
Fibre Types ◽  
Production Cycle ◽  
Wool Production ◽  
Apparent Change ◽  
The Mean

1. Seasonal changes in wool production per unit area of unstretched skin, number of fibres of each type per unit area, ratio of fibre types, mean fibre weights, lengths and diameters and degree of medullation are given. The production cycle shows a peak in August and September and a trough in February and March, the weight of wool produced in the latter period being only 16% of that in the former. Approximately 80% of the fleece is produced in the 6 months from June to November (lambing ewes). Other components show similar trends.2. The production cycle does not entirely coincide with the nutritional cycle as estimated from bodyweight changes before late pregnancy. Whilst bodyweight increases from September to November wool production declines by about 25%.3. The winter drop in wool production per unit area is caused partly by a decrease in the mean weight of each fibre type (in turn made up of a decrease in both length and diameter) and partly by a 50% reduction in the number of active fine fibre follicles and a 100% reduction in active kemp follicles. There is no apparent change in the number of active coarse fibre follicles. The degree of medullation of both coarse and fine fibres declines substantially between December and May.

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