Snow cover variability and snowmelt in a high-altitude ungauged catchment

Abstract. Mining activities in cold regions are vulnerable to snow avalanches. Unlike operational facilities, which can be constructed in secure locations outside the reach of avalanches, access roads are often susceptible to being cut, leading to mine closures and significant financial losses. In this paper we discuss the application of avalanche runout modelling to predict the operational risk to mining roads, a long-standing problem for mines in high-altitude, snowy regions. We study the 35 km long road located in the "Cajón del rio Blanco" valley in the central Andes, which is operated by the Codelco Andina copper mine. In winter and early spring, this road is threatened by over 100 avalanche paths. If the release and snow cover conditions can be accurately specified, we find that avalanche dynamics modelling is able to represent runout, and safe traffic zones can be identified. We apply a detailed, physics-based snow cover model to calculate snow temperature, density and moisture content in three-dimensional terrain. This information is used to determine the initial and boundary conditions of the avalanche dynamics model. Of particular importance is the assessment of the current snow conditions along the avalanche tracks, which define the mass and thermal energy entrainment rates and therefore the possibility of avalanche growth and long runout distances.

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Observed high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-1303-2016 ◽

2016 ◽

Vol 16 (3) ◽

pp. 1303-1315 ◽

Cited By ~ 43

Author(s):

Y. Xu ◽

V. Ramanathan ◽

W. M. Washington

Keyword(s):

Tibetan Plateau ◽

High Altitude ◽

Snow Cover ◽

Black Carbon ◽

Global Climate Model ◽

Anthropogenic Factors ◽

Climate Projections ◽

The Tibetan Plateau ◽

Surface Warming ◽

Snow Cover Extent

Abstract. Himalayan mountain glaciers and the snowpack over the Tibetan Plateau provide the headwater of several major rivers in Asia. In situ observations of snow cover extent since the 1960s suggest that the snowpack in the region have retreated significantly, accompanied by a surface warming of 2–2.5 °C observed over the peak altitudes (5000 m). Using a high-resolution ocean–atmosphere global climate model and an observationally constrained black carbon (BC) aerosol forcing, we attribute the observed altitude dependence of the warming trends as well as the spatial pattern of reductions in snow depths and snow cover extent to various anthropogenic factors. At the Tibetan Plateau altitudes, the increase in atmospheric CO2 concentration exerted a warming of 1.7 °C, BC 1.3 °C where as cooling aerosols cause about 0.7 °C cooling, bringing the net simulated warming consistent with the anomalously large observed warming. We therefore conclude that BC together with CO2 has contributed to the snow retreat trends. In particular, BC increase is the major factor in the strong elevation dependence of the observed surface warming. The atmospheric warming by BC as well as its surface darkening of snow is coupled with the positive snow albedo feedbacks to account for the disproportionately large role of BC in high-elevation regions. These findings reveal that BC impact needs to be properly accounted for in future regional climate projections, in particular on high-altitude cryosphere.

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Sunscreen for adventure travel: use sun protection factor 50 or higher

Journal of Travel Medicine ◽

10.1093/jtm/taaa048 ◽

2020 ◽

Vol 27 (6) ◽

Author(s):

Ken Zafren

Keyword(s):

High Altitude ◽

Snow Cover ◽

Uv Radiation ◽

Broad Spectrum ◽

Sun Protection ◽

Protection Factor ◽

Low Latitude ◽

Adventure Travel ◽

Exposed Skin ◽

Sun Protection Factor

For adventure travel to high altitude and low latitude locations as well as to areas with depleted ozone or snow cover, travelers should use clothing that blocks UV radiation and should liberally apply a broad spectrum sunscreen with an SPF of 50 or 50+ to exposed skin.

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Observed high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-19079-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 19079-19109 ◽

Cited By ~ 8

Author(s):

Y. Xu ◽

V. Ramanathan ◽

W. M. Washington

Keyword(s):

Tibetan Plateau ◽

High Altitude ◽

Snow Cover ◽

Black Carbon ◽

Global Climate Model ◽

Anthropogenic Factors ◽

Climate Projections ◽

The Tibetan Plateau ◽

Surface Warming ◽

Snow Cover Fraction

Abstract. Himalayan mountain glaciers and the snowpack over the Tibetan Plateau provide the headwater of several major rivers in Asia. In-situ observations of snow cover fraction since the 1960s suggest that the snow pack in the region have retreated significantly, accompanied by a surface warming of 2–2.5 °C observed over the peak altitudes (5000 m). Using a high-resolution ocean–atmosphere global climate model and an observationally constrained black carbon (BC) aerosol forcing, we attribute the observed altitude dependence of the warming trends as well as the spatial pattern of reductions in snow depths and snow cover fraction to various anthropogenic factors. At the Tibetan Plateau altitudes, the increase of atmospheric CO2 concentration exerted a warming of 1.7 °C, BC 1.3 °C where as cooling aerosols cause about 0.7 °C cooling, bringing the net simulated warming consistent with the anomalously large observed warming. We therefore conclude that BC together with CO2 has contributed to the snow retreat trends. Especially, BC increase is the major factor in the strong elevation dependence of the observed surface warming. The atmospheric warming by BC as well as its surface darkening of snow are coupled with the positive snow albedo feedbacks to account for the disproportionately large role of BC in high-elevation regions. These findings reveal that BC impact needs to be properly accounted for in future regional climate projections, in particular on high-altitude cryosphere.

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MODIS Imagery Based Water Content Forecasting Methodology for Mountain Rivers in Central Asia

Central Asian Journal of Water Research ◽

10.29258/cajwr/2020-r1.v6-2/66-78.eng ◽

2020 ◽

Vol 6 (2) ◽

pp. 66-78

Author(s):

◽

O.Yu. Kalashnikova ◽

A.A. Gafurov

Keyword(s):

High Altitude ◽

Snow Cover ◽

Water Content ◽

River Water ◽

Decision Makers ◽

Mountain Rivers ◽

Short Term ◽

Economic Sectors ◽

Central Asian ◽

Modis Imagery

The article investigates the possibility of using snow cover satellite data for short-term hydrological forecasting for Central Asian rivers with high-altitude catchments. The research aimed to elaborate a methodology for forecasting mean 10-day (decadal) river discharge (MDD) of the Varzob and Tar Rivers based on MODSNOW-processed MODIS satellite imagery. The objectives of the study were to calculate the snow cover index (SCI) for high-altitude zones in 200 m increments for selected river basins, and to analyze the closeness of dependency between the corresponding SCIs and MDDs. The research resulted in equations applicable for producing operational river water content forecasts. Timely and reliable information on expected river water content during the forthcoming 10-day period allows decision makers (water management and hydropower agencies, emergency authorities) plan water supply for various economic sectors, as well as take measures to prevent hazardous hydrological phenomena on the rivers of Tajikistan and Kyrgyzstan.

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Glacier retreat and its impact on summertime run-off in a high-altitude ungauged catchment

Hydrological Processes ◽

10.1002/hyp.11287 ◽

2017 ◽

Vol 31 (21) ◽

pp. 3672-3681 ◽

Cited By ~ 5

Author(s):

Rui Wang ◽

Zhijun Yao ◽

Shanshan Wu ◽

Zhaofei Liu

Keyword(s):

High Altitude ◽

Glacier Retreat ◽

Ungauged Catchment ◽

Run Off

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Shift in seasonal snowpack melt-out date due to light-absorbing particles at a high-altitude site in Central Himalaya

10.5194/acp-2021-158 ◽

2021 ◽

Author(s):

Johan Ström ◽

Jonas Svensson ◽

Henri Honkanen ◽

Eija Asmi ◽

Nathaniel B. Dkhar ◽

...

Keyword(s):

High Altitude ◽

Snow Cover ◽

Energy Budget ◽

Snow Water Equivalent ◽

Base Case ◽

Snow Melt ◽

Central Himalayas ◽

Seasonal Snow ◽

The Impact ◽

Seasonal Snow Cover

Abstract. Snow darkening by deposited light-absorbing particles (LAP) has the potential to accelerate snowmelt and shift the snow melt-out date. Here we investigate the sensitivity of the seasonal snow cover duration to changes in LAP at a high altitude valley site in the Central Himalayas, India. First, the variation of the albedo of the seasonal snow was emulated using two seasons of automatic weather station (AWS) data and applying a constant, but realistic deposition of LAP to the snow. Then, the number of days with snowmelt were evaluated based on the estimated net energy budget of the seasonal snow cover and the derived surface temperature. The impact on the energy budget by LAP combined with the melt-day analysis resulted in very simple relations to determine the contribution of LAP to the number of days with snowmelt of the seasonal snow in Himalaya. Above a concentration of 1 ng g-1 (Elemental Carbon equivalent, ECeq, which in this study includes EC and the absorption equivalent EC contribution by other light absorbing particles, such as mineral dust) in new snow, the number of days with snowmelt can be estimated by; days=0.0109(log⁡(〖EC〗_eq )+1)PP±0.0033(log⁡(〖EC〗_eq )+1)PP, where PP is the seasonal precipitation in mm snow water equivalent. A change in ECeq by a factor of two corresponds to about 1/3 of a day per 100 mm precipitation. Although the change in the number of days with melt caused by the changes in ECeq is small, the estimated total change in the snow melt-out date by LAP can be significant. For our realistic base case scenario for the Sunderdhunga Valley, Central Himalayas, India, of ECeq=100 ng g-1 and PP=400 mm, this yields in an advancement of the melt-out date of about 13 days.

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Contrast of Filament Bright Rims

International Astronomical Union Colloquium ◽

10.1017/s0252921100025628 ◽

1994 ◽

Vol 144 ◽

pp. 365-367

Author(s):

E. V. Kononovich ◽

O. B. Smirnova ◽

P. Heinzel ◽

P. Kotrč

Keyword(s):

High Altitude ◽

Line Profile ◽

Line Center ◽

Magnetic Structures ◽

The Mean

AbstractThe Hα filtergrams obtained at Tjan-Shan High Altitude Observatory near Alma-Ata (Moscow University Station) were measured in order to specify the bright rims contrast at different points along the line profile (0.0; ± 0.25; ± 0.5; ± 0.75 and ± 1.0 Å). The mean contrast value in the line center is about 25 percent. The bright rims interpretation as the bases of magnetic structures supporting the filaments is suggested.

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Clean Electron Microscope Substrate Films Used for Micrometeorite Collection and Study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061847 ◽

1967 ◽

Vol 25 ◽

pp. 366-367

Author(s):

D. M. Davies ◽

R. Kemner ◽

E. F. Fullam

Keyword(s):

Thin Film ◽

Electron Microscope ◽

High Altitude ◽

Amyl Acetate ◽

Temperature Variations ◽

Film Forming ◽

Film Specimen ◽

Particulate Contaminants

All serious electron microscopists at one time or another have been concerned with the cleanliness and freedom from artifacts of thin film specimen support substrates. This is particularly important where there are relatively few particles of a sample to be found for study, as in the case of micrometeorite collections. For the deposition of such celestial garbage through the use of balloons, rockets, and aircraft, the thin film substrates must have not only all the attributes necessary for use in the electron microscope, but also be able to withstand rather wide temperature variations at high altitude, vibration and shock inherent in the collection vehicle's operation and occasionally an unscheduled violent landing.Nitrocellulose has been selected as a film forming material that meets these requirements yet lends itself to a relatively simple clean-up procedure to remove particulate contaminants. A 1% nitrocellulose solution is prepared by dissolving “Parlodion” in redistilled amyl acetate from which all moisture has been removed.

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