The Problem of Short period measurements of Snow Ablation

Hubley, Richard C.

doi:10.3189/002214354793702542

Cited by 16 publications

(6 citation statements)

References 4 publications

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“…Hubley (1954) formulated an expression for the ablation which takes care of these changes and presented all quantities involved as functions of time:…”

Section: Theory and Measurementsmentioning

confidence: 99%

Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements

Föhn

1973

J. Glaciol.

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The daily snow melt calculated from meteorological observations is compared with detailed mass-balance measurements taking into account internal changes in density and free water content in the surface layers of a glacier snow-pack. The energy balance is calculated from measurements obtained by a meteorological station at the experimental site. In addition to the standard ablation measurements the run-off from the melting snow-pack was obtained for a few days. The snow-density profiles were measured with a portable gamma-transmission probe and the liquid-water content of snow was determined by a calorimetric method.Agreement between the melt calculated by the heat-balance method and the mass changes observed in the mass-balance measurements is fair for daily periods. It appears that about 20% of the daily snow melt takes place internally as a result of penetration of solar radiation.

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“…Hubley (1954) formulated an expression for the ablation which takes care of these changes and presented all quantities involved as functions of time:…”

Section: Theory and Measurementsmentioning

confidence: 99%

Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements

Föhn

1973

J. Glaciol.

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“…Hubley (1954) discussed the problems for the case of snow from a theoretical point of view and presented an equation for ablation which includes both changes in surface level and density as functions of time.…”

Section: Direct Measurement Of Mass Lossmentioning

confidence: 99%

Errors in Short-Term Ablation Measurements on Melting Ice Surfaces

1969

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Rapid changes in time and space in the micro-relief of an ablating glacier surface and radiation-induced melt within the uppermost ice layer, termed the “weathering crust”, seriously affect the accuracy of the short-term ablation measurements. The various measuring techniques commonly used (stakes, ablatometers, ablatographs) and some new methods (measurement of discharge from a small supra-glacial drainage basin, and mass loss directly measured on core samples) are critically reviewed and assessed in the light of these phenomena. The implications for studies of heat and mass balance are discussed.It appears that the direct measurement of mass flux is the most accurate means of assessing short-terni ablation rates. The errors in short-term ablation measurements by any method are largely compensatory and consequently do not influence long-period mass-balance estimates.

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“…Meas urements of surface ablation of snow on Lemon Creek Glacier by La Chapelle [1954] have shown that at least over short periods of time, the rate of lowering of the snow surface is not indicative of the rate of ablation. It has been shown in an earlier paper [Hubley, 1954] that in a vertical column of unit cross-sectional area extending from the base of the snowpack, 2 -0, to the upper surface, z =* h, the rate of melt, dmi/dt, can be expressed…”

Section: Exchangementioning

confidence: 99%

An analysis of surface energy during the ablation season on Lemon Creek Glacier, Alaska

Hubley¹

1957

Eos Trans. AGU

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The purpose of the present study has been to perform an empirical investigation of the energy transfer at an isothermal, melting snow surface and its relationship to observed meteorological parameters, using more refined instrumentation and methods of observation than were available in earlier, similar investigations by H. U. Sverdrup and C. C. Wallen. The thickness of the surface layer of snow through which absorption of solar radiation occurs is determined from measurements of intensities of visible radiation within the snow. Albedo values for the snow are computed from measurements of incoming and reflected solar radiation over the snow surface. The snow albedo is found to vary with solar altitude and cloudiness as well as with changes in physical characteristics of the snow. When long‐wave radiation is considered along with solar radiation, it is found that during the ablation season, the diurnal net transfer of radiant energy to the melting snowpack is often greater when skies are overcast than when skies are clear. A comparison is made between the radiative energy transfer at the surface of a model glacier in the Juneau Ice Field, and a model glacier in the Alps. It is shown that energy transfer to the snow by rain falling on an isothermal melting snowpack is an insignificant part of the total energy transfer. From measured and calculated values of net energy transfer at the snow surface, energy transfer by radiation, and energy transfer by rain, values of energy transfer by turbulence are determined for a series of selected observation periods. These values are used to calculate exchange coefficients. It is shown that by making a slight modification in the functional expression for heat transfer by turbulence from that used by Sverdrup and Wallén, it is possible to obtain a nearly invariant relationship between the heat transfer by turbulence, windspeed, and the vertical temperature distribution above the surface when an inversion is present. It is found that turbulent transfer of heat is the most important factor in causing ablation on the Lemon Creek Glacier. This turbulent transfer of energy becomes very large during summer storm periods. As a result, the number of warm storms passing over the glacier in a single ablation season can largely determine whether the glacier will end the season with a positive or negative mass budget.

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The Problem of Short period measurements of Snow Ablation

Cited by 16 publications

References 4 publications

Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements

Short-Term Snow Melt and Ablation Derived from Heat- and Mass-Balance Measurements

Errors in Short-Term Ablation Measurements on Melting Ice Surfaces

An analysis of surface energy during the ablation season on Lemon Creek Glacier, Alaska

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