Snow-covered Surfaces Research Articles

Bank-erosion processes in a cool-temperate environment, Orwell Lake, Minnesota

Orwell Lake, in west-central Minnesota, is a flood-control, water-management reservoir first impounded in 1953. Subsequent concern about erosion of the shoreline and a lack of knowledge of slope-erosion processes in this part of the upper Midwest prompted this study to identify and quantify the processes there. The processes were measured at selected sites between June 1980 and June 1983. Erosion of the banks is predominantly by thaw failure and secondarily by rainsplash and sheetwash. In winter, the upland surface adjacent to the lake freezes to a depth of between 1 and 2 m, depending on surface temperature, snow cover, and distance from exposed banks. In late winter, soil aggregates, released by the sublimation of interstitial ice within the banks, begin to accumulate at the base of the slopes, often veneering snowbanks. As soon as thaw begins, slab failure of bank sediment is followed by mudflows and earthflows. Thaw failure at Orwell Lake in the spring of 1982 accounted for 89% of the erosion (824 Mg); the following spring, 78% (746 Mg). Such slope failure is most intense along north-facing banks and considerably less intense on south-facing banks, where more effective desiccation and sublimation reduce soil-moisture content. Summer rainsplash and sheetwash were responsible for 11%–22% of the total erosion, amounting to 102 Mg in 1981 and 208 Mg in 1982. Although rainsplash is the most consistent process during summer, the occasional storm during which rainwash occurs causes greater total erosion. Erosion by rain increased in each of the three summers, largely because of increased precipitation. Infrequent massive deep-slip failures (slumps) have occurred at the east end of the lake where a buried clay-rich unit is stratigraphically and topographically positioned to favor such failures. Drought years followed by heavy spring rains probably will result in additional deep-slip slope failures.

Remote sensing of weather and climate parameters from HIRS2/MSU on TIROS‐N

At the Goddard Laboratory for Atmospheric Sciences (GLAS) we have developed a physically based satellite temperature sounding retrieval system, involving the simultaneous analysis of HIRS2 and MSU sounding data, for determining atmospheric and surface conditions which are consistent with the observed radiances. In addition to determining accurate atmospheric temperature profiles even in the presence of cloud contamination, the system provides global estimates of day and night sea or land surface temperatures, snow and ice cover, and parameters related to cloud cover. The inverse radiative transfer equation approach to the multi‐spectral analysis of the data, and details of its implementation, are described. Ice, snow, and cloud fields derived for January 1979 are consistent with other measures of similar parameters obtained from AVHRR and SMMR. Monthly mean sea‐surface temperature fields agree with those derived from ship and buoy measurements to 0.5°C.

Seasonal variation in the radiation regime of a dwarf apple orchard

Seasonal and daily radiation fluxes showed that the highest monthly albedo was 0.81 in January compared with a growing season mean of about 0.20. These differences correspond to dramatic changes in the surface characteristics with season. Patterns in photosynthetically active radiation were similar to those for incoming solar irradiance. The highest values of incoming long-wave radiation were on days with high temperatures and overcast skies, whereas outgoing long-wave radiation exhibited a midwinter minimum in January corresponding to a cold snow-covered surface. Net radiation was negative in the winter months but increased almost linearly in the late winter, spring, and early summer months. An understanding of these components of the radiation regime which drive the photosynthetic system may be useful in assessing winter injury or crop development during the growing season.

A Global Low-Order Spectral General Circulation Model. Part II: Diagnosis of the Seasonal Energetics

The purpose of this paper is to document the seasonal variation of the atmospheric energy cycle simulated by a low-resolution general circulation model in order to assess the model's strengths and weaknesses and better define its usefulness for future sensitivity studies. The numerical model is a global, spectral, primitive equation model with five equally-spaced sigma levels in the vertical and triangular truncation at wavenumber 10 in the horizontal. Included in the model are: orography; time-varying (but prescribed) sea surface temperature, snow cover, and solar declination angle; parameterizations of radiation, convection, condensation, diffusion, and surface transports; and a surface heat budget. The model simulates the observed vertically-integrated energetics of the troposphere reasonably well and the values are comparable to other general circulation models. At northern extratropical latitudes, the very long waves, wavenumbers 1 through 3, which are associated with thermal and orographic zonal asymmetries, dominate the model energy cycle. The annual cycle prevails, with maximum values approximately one month after the winter solstice. These model aspects are similar to those documented observationally. Analysis of the time variation of the model energetics details the presence of asymmetric and steplike variations superimposed on the annual cycles at northern extratropical latitudes. The. model statistics also reveal important latitudinal variations. In particular, more sinusoidal seasonal cycles and a predominance of energy at wavenumbers 4 through 7 are found at southern extratropical latitudes, and the thermally direct east-west circulations, associated with land-sea and precipitation zonal asymmetries, are important in the tropical energy cycle. The major discrepancies in the model simulation of the atmospheric energy cycle are the overestimation of zonal and eddy available potential energy and the conversion between them, an exaggerated semiannual component in the seasonal cycle of eddy available potential energy, a deficiency of eddy kinetic energy at the jet core level, and an underestimation of the transients. The model limitations leading to these discrepancies are discussed, as well as improvements made in subsequent versions of the model.

Practical Applications of a Versatile Geothermal Simulator

Since 1976, the author has programmed, developed and applied a versatile two-dimensional geothermal simulator for many interesting applications in cold regions engineering. This paper concentrates on applications to problems which have not been hitherto easily solved by other available geothermal models. Some of the important capabilities of the HAL simulator are: (i) radial or cartesian coordinate options, (ii) convective ground water flow component, (iii) simple data entry, (iv) ability to specify internal “pipes,” or areas of specified temperature, (v) monthly surface temperature and snow cover inputs as boundary conditions. The first application involves a steel pile, embedded in warm permafrost. A circular cryogenic storage tank is studied next, and the effectiveness of an insulation layer is illustrated. The convection option in the program is invoked when studying the effects of ground water flow around a series of vertical freeze pipes. Finally, the thermal degradation beneath an Arctic lake is studied, and the subsequent refreezing and growth of a pingo has been simulated.

Formulation and testing of a climatonomic simulation of the microclimate of the dry valleys and of the little America v station in Antarctica

A climatonomy model to synthesize monthly-mean energy fluxes and temperatures for a snow-covered and snow-free surface in the Antarctic is described. The system is composed of two submodels based on simple, bulk parameterization of physical processes. The first describes the scattering and absorption of global radiation by the atmosphere, while the second partitions the surface fluxes at the ground and predicts their time-series values over the annual cycle.

Spectral Radiation Modeling for the Antarctic Plateau: Effects of Clouds, Ozone and CO2 ON THE Radiation Budget(Abstract only)

The radiation balance at and above a snow-covered surface is affected not only by the high general level of the surface albedo, but also by the strong spectral variation of that albedo. Furthermore, the fact that clouds and snow have highly correlated optical properties means that the radiative problem of clouds over a snow surface is a particularly difficult one. Both for its own intrinsic interest, and because it is in many ways as clear an example of snowatmosphere radiative interactions as one is likely to find, we have chosen to make spectrally detailed model calculations of solar and long-wave radiation over Antarctica using an atmospheric radiation model of Wiscombe (1975) coupled to the recent snow reflectivity model of Wiscombe and Warren (1980). Typical clear and cloudy situations are studied. Radiative fluxes are examined particularly at the surface and the top of the atmosphere since these are the locations of most past and future measurements. Radiation budget calculations are compared with observations at Plateau station for various sun angles and cloud conditions. The effects on the radiation balance of a sub-visible ice-crystal cloud (“clear-sky ice-crystal precipitation”), as well as observed water clouds over the snow surface are investigated. Because the snow of the Antarctic plateau is very clean, falls throughout the summer, and never melts, we can make accurate calculations of the surface albedo using our model for fine-grained snow. The absorbed solar radiation at the surface is almost entirely in the near-infrared where snow albedo is considerably lower than its visible values. Snow-surface albedo increases with zenith angle for all sun angles. The spectrally integrated planetary albedo is about 10% less than the surface albedo and shows the same zenith-angle dependence for high sun. But for solar zenith angles greater than about 70° the planetary albedo may show a contrary trend because the increased atmospheric absorption in the long slant path overwhelms the zenith-angle dependence of the snow albedo. Clouds raise the spectrally integrated planetary albedo because the cloud particles are smaller, on average, than the snow grains. Clouds raise the surface albedo by absorbing near-infrared radiation and thus altering the spectral distribution of the solar radiation reaching the surface. The Antarctic atmosphere is so dry that more solar radiation may actually be absorbed by ozone than by water vapor, even for a water-vapor saturated troposphere, in contrast to the situation elsewhere. As the solar absorption due to ozone is enhanced by the lack of water vapor, so is the absorption due to C02. Because some of the water-vapor absorption bands overlap CO2 absorption bands, the radiation budget is more sensitive to CO2 variations in the Antarctic than elsewhere. The radiation-budget effects of possible future increases as well as the likely Pleistocene reductions of atmospheric CO2 are investigated. This paper will be submitted in full to the Journal of Geophysical Research. This research was supported by US National Science Foundation grant ATM-80-24641. The computations were done at the National Center for Atmospheric Research.

Spectral Radiation Modeling for the Antarctic Plateau: Effects of Clouds, Ozone and CO2 ON THE Radiation Budget(Abstract only)

The radiation balance at and above a snow-covered surface is affected not only by the high general level of the surface albedo, but also by the strong spectral variation of that albedo. Furthermore, the fact that clouds and snow have highly correlated optical properties means that the radiative problem of clouds over a snow surface is a particularly difficult one.Both for its own intrinsic interest, and because it is in many ways as clear an example of snowatmosphere radiative interactions as one is likely to find, we have chosen to make spectrally detailed model calculations of solar and long-wave radiation over Antarctica using an atmospheric radiation model of Wiscombe (1975) coupled to the recent snow reflectivity model of Wiscombe and Warren (1980). Typical clear and cloudy situations are studied. Radiative fluxes are examined particularly at the surface and the top of the atmosphere since these are the locations of most past and future measurements.Radiation budget calculations are compared with observations at Plateau station for various sun angles and cloud conditions. The effects on the radiation balance of a sub-visible ice-crystal cloud (“clear-sky ice-crystal precipitation”), as well as observed water clouds over the snow surface are investigated.Because the snow of the Antarctic plateau is very clean, falls throughout the summer, and never melts, we can make accurate calculations of the surface albedo using our model for fine-grained snow. The absorbed solar radiation at the surface is almost entirely in the near-infrared where snow albedo is considerably lower than its visible values.Snow-surface albedo increases with zenith angle for all sun angles. The spectrally integrated planetary albedo is about 10% less than the surface albedo and shows the same zenith-angle dependence for high sun. But for solar zenith angles greater than about 70° the planetary albedo may show a contrary trend because the increased atmospheric absorption in the long slant path overwhelms the zenith-angle dependence of the snow albedo.Clouds raise the spectrally integrated planetary albedo because the cloud particles are smaller, on average, than the snow grains. Clouds raise the surface albedo by absorbing near-infrared radiation and thus altering the spectral distribution of the solar radiation reaching the surface.The Antarctic atmosphere is so dry that more solar radiation may actually be absorbed by ozone than by water vapor, even for a water-vapor saturated troposphere, in contrast to the situation elsewhere.As the solar absorption due to ozone is enhanced by the lack of water vapor, so is the absorption due to C02. Because some of the water-vapor absorption bands overlap CO2 absorption bands, the radiation budget is more sensitive to CO2 variations in the Antarctic than elsewhere. The radiation-budget effects of possible future increases as well as the likely Pleistocene reductions of atmospheric CO2 are investigated.This paper will be submitted in full to the Journal of Geophysical Research. This research was supported by US National Science Foundation grant ATM-80-24641. The computations were done at the National Center for Atmospheric Research.

The January and July Performance of the OSU Two-Level Atmospheric General Circulation Model

A modified version of the two-level atmospheric general circulation model has been developed and used in the simulation of January and July global climates. The overall physical and numerical formulation of this Oregon State University (OSU) model is the same as that described previously by Gates and Schlesinger (1977), but in the new version water vapor at the upper level has been made a prognostic variable, the parameterizations of cumulus convection, large-scale condensation and evaporation, clouds and radiative-transfer have been changed, the surface snow mass and ground temperature have been made prognostic variables, and the treatment of the surface boundary layer has been revised. Modifications have also been made in the numerical solution procedure (which have increased the model’s speed by nearly a factor of 2), and in the prescribed distributions of topography, sea surface temperature and sea ice. The surface albedo is now a function of the prescribed surface type and of the predicted surface snow cover. The model simulates most features of the large-scale distributions of observed January and July climate more accurately than before, including the primary variables of pressure, temperature, wind, cloudiness and precipitation. In addition, the simulated meridional transports of zonal momentum, heat and water vapor are closer to those observed than heretofore, as are the elements of the associated heat and hydrologic balances. The energy cycle is also simulated with greater accuracy, although the zonal potential and kinetic energies are still somewhat overestimated by the model while the eddy kinetic energy is underestimated. The markedly improved simulations of precipitation, evaporation, 400 mb temperature and surface sensible heat flux in the tropics are shown to be due to the revisions in the new model’s boundary-layer parameterization.

Avalanche Protective Effect of Young Broad-leaved Forests

During the winter of 1968-1977 the relation between the growth of young broad-leaved forests and the snow glide was investigted on mountain slopes in Tokamachi city, Niigata Prefecture. It was observed that snow glide was greatly affected by the total number of trees, the tips of which appeared on the surface of snow cover of 2-3m in depth and those which were buried under the snow cover; the stems were over 6 cm in diameter. Avalanches tended to occur in the forests in which the number of trees was less than 3, 000/ha. When the number of trees increased to more than 4, 500/ha, the snow glide decreased to 2-3m in a winter and the snow cover became stable. It appeared that the snow cover on the southern slopes became stable in 10-15 years after regeneration felling and the same was observed on the northern slopes in 20-25 years.

Development of water veins along the three-grain intersection in fresh water ice at the melting point

This paper describes an experimental study on the development of water veins along three-grain intersections in pure water ice kept at the melting point. The diameter of a water vein D (μm) increases with the lapse of time t (hours) : D=2.61t0.56. Results of the experiment are applied to explain the formation of radially-grown meltpatterns on the snow-covered surface of lake ice. This pattern has been observed as a result of gushing of water through a hole formed in the snow-covered ice. As one of the causes contribuing to the formation of watergushing holes, the water vein development along the three-grain intersections in crystal grain boundaries is experimentally examined. Further, the effect of light irradiation on the ice sample is investigated in relation to the enhancement of formation of water veins.

Studies on the Attenuation of Quasi Millimeter Wave on a Rain and Snow Covered Radome

The quasi millimeter wave performance suffers degradation under rain, due to the high loss tangent of water in the quasi millimeter wave region. This effect cannot be theoretically estimated due to the complex nature of water flow on the radome surface. The above special effect is observed also in the case of snow-covered surface of the dome.In order to ascertain the above-mentioned effect, some model tests were performed. The main results are summarized as follows : (1) Laboratory tests on the effects of water accretion on the radome surfaceThe surface area of the radome used in this experiment is 50cm×50cm, and the frequency used is 24 GHz. It is found that attenuation factor vs. thickness of water film becomes about 18dB/mm. And attenuation factor vs. area percentage of stringy flow of running water is correlative.(2) Field tests on the effects of snow accretion on the practical radome surfaceThe aperture size of the practical radome used in this experiment is 3.3 meters, and this radome is made of dielectric plates (laminated polyester resin reinforced with glass fiber).Diurnal variations of snow accretion on the above radome were observed in the winter of 1973. The maximum thickness of accreted snow layer was about 60 cm. The condition of snow accretion varied quickly over a wide range chiefly with air temperature, especially above 0°C, and with weather conditions (sunny or shaded sides of the radome).

Seasonal Albedo Variation of Black Spruce and Sphagnum-Sedge Bog Cover Types

Abstract Albedo measurements were made over two northern Minnesota bog cover types. Two Kipp and Zonen pyranometers were cycled over black spruce [Pica mariana (Mill.) B.S.P.] and sphagnum-sedge bog canopies within a one year period. During the snow-free seasonal periods black spruce had a 6–8% albedo and did not exhibit a response to new shoot growth and maturation. Albedo increased to 8.2% with an 80% bog surface snow cover in late November while a 100% bog surface snow cover increased the albedo to 10.5% in February–March. The sphagnum-sedge bog exhibited an increase from 11.6% in April–May to 16.1% in June with a gradual decline to 13.5% in October–November. A 50–60% old snow cover increased the November–December albedo to 35.1% while the albedo of a fresh continuous snow cover in February–March was 81.7%. The effect of cloud cover on the albedo was negligible.

Large Strain FE-analyses Of Localized FailureIn Snow

An algorithm for finite deformation plasticity theory, recently proposed by Simo [5] and Simo and Meschke [6], is applied to numerical simulations of localized failure in snow. Within the algorithmic framework for finite strain plasticity the classical Drucker-Prager model and the modified Cam-Clay model are employed for the representation of snow. The respective material parameters are calibrated according to results from hydrostatic and shear-box tests of snow specimen. The effectiveness of the FE-model is demonstrated by means of re-analyses of the shear-box test, characterized by the formation of a sharp, localized failure zone. The traction mechanism of a single automobile tread moving over a snow-covered road surface is numerically simulated. The predicted failure mechanism of snow in consequence of the movement of the tread agrees relatively well with respective experimental observations. INTRODUCTORY REMARKS This paper is concerned with the numerical investigation of the traction behavior of automobile tires on snow-covered road surfaces by means of the finite element method (FEM). This type of analysis involves realistic modelling of rubber, snow and the contact at the rubber-snow interface. The traction behavior of tires for winter conditions is characterized by a complex mechanical interaction between the treads of the tires and the snow. The snow in the vicinity of the treads is subjected to large plastic deformations associated with the appearance of localized failure zones. The occurance of large non-recoverable deformations suggests using the of classical plasticity theory, embedded in the geometrically nonlinear theory of finite strain Transactions on Engineering Sciences vol 6, © 1994 WIT Press, www.witpress.com, ISSN 1743-3533 462 Localized Damage plasticity, for the modelling of snow. Relatively little research work concerning 3D constitutive models for snow is found in the open literature. In a recent work by Mohamed, Yong and Murcia [1] it is assumed that snow follows a ,/2-type of plasticity law. However, this simplified model does not account for the considerable plastification of snow when subjected to hydrostsatic pressure. Salm [4] proposed a viscoelastic constitutive law restricted to uniaxial stress states. The present numerical investigation has been accompanied by an experimental investigation of snow specimens involving hydrostatic and shear-box tests. The results of this series of tests suggest the 'critical state concept', widely used in geomechanics, to be an adequate representation of the constitutive behavior of snow. In the present analyses, the (modified) Cam-Clay model, recast within a recently proposed algorithmic framework for finite strain plasticity [5], [6] is employed. This algorithm is formulated on the basis of hyperelasticity in the current configuration, with the elastic region being defined in terms of Kirchhoff stresses. The key advantage of this method is that the structure of the return mapping algorithm of the infinitesimal theory can be taken over to the nonlinear theory without modification. A fully implicit algorithmic treatment of the nonlinear elastic constitutive law along with an implicit integration of the flow rule on the basis of the return mapping algorithm is used. The Cam-Clay model is calibrated by means of the hydrostatic and the shear-box tests, respectively. For comparison, an elastic, ideally-plastic Drucker-Prager model is adopted. The important issue of viscosity of snow is not considered in this paper. It will be addressed in a follow-up publication. Both models for snow are applied in the re-analyses of shear-box tests. As far as the Drucker-Prager model is concerned, a comparison between the new plasticity algorithm with the standard incremental hypoelastic formulation, implemented in the multipurpose program MARC is presented. The obtained results are compared with experimental data. Numerical simulations of the traction mechanism of a single automobile tread moving on a snow-covered surface, based on the Cam-Clay model for snow, are performed. REMARKS ON FINITE STRAIN PLASTICITY The extension of the classical (modified) Cam-Clay plasticity model to the finite strain regime is based on an algorithm for finite strain plasticity recently proposed by Simo [5] and Simo and Meschke [6]. The key ingredients of this algorithm are briefly outlined below: The stress response is governed by a hyperelastic law, characterized by a function of stored energy, W(F ) involving the elastic part of the deformation gradient, F*. The restriction to isotropy implies that W(F*) = M (b ), where b* is the elastic part of the left Cauchy-Green tensor. The total deTransactions on Engineering Sciences vol 6, © 1994 WIT Press, www.witpress.com, ISSN 1743-3533

Atmospheric Light Transmission in a Wisconsin Area

A technique is described for measuring hitherto unavailable, long range, air-to-ground total and direct transmittances simultaneously in the visible and near ir spectral regions from a point source in a real atmosphere. The technique involves a radar tracked aircraft with a flashing light source and a ground based, highly sensitive, multichannel, 180 degrees field-of-view light receiving system with manual tracking provisions. Air-to-surface transmission measurements were carried out to maximum slant range of 100,000 yards (92 km) at different altitudes and weather conditions over Lake Michigan and Wisconsin farm land during March 1965. Total transmittances vs slant range for the visible and near ir regions are presented as smoothed, average curves and simplified exponential equations representing the least-square fit to the experimental data under specific weather conditions. Criteria for evidence of surface albedo differences are introduced, from which limited albedo effects are noted under cloudy, snow-covered surface conditions.

Wavelength dependence of the radar reflectivity of the Earth and the Moon

Recent interest in the use of a multifrequency radar as a remote sensor for exploration of the earth and the moon has stimulated this study of the variation of radar backscattering with change in electromagnetic wavelength. The analysis of data has shown that radar cross sections of land and sea surfaces decrease with increasing wavelength and, on the average, follow approximately a λ−1 behavior, although the exponent may vary from +2 to −6 in individual cases. Snow-covered surfaces at all depression angles and sea surfaces at angles above 73° are the ones with positive values for the exponent. The wavelength dependence of the moon and the average values found on the earth in this study are quite similar. The combination of polarization and wavelength dependence versus depression angle may be characteristic features for distinguishing various terrain types by a multifrequency radar.

STUDY OF A CONTINENTAL SURFACE ALBEDO ON THE BASIS OF FLIGHT MEASUREMENTS AND STRUCTURE OF THE EARTH'S SURFACE COVER OVER NORTH AMERICA*

A series of 12 monthly flights along a fixed path in Wisconsin and a series of 4 long-range flights over extensive areas of the United States and Canada were performed during 1963 to measure systematically the surface albedo over various types of the earth's surface, using an instrumented light airplane operating at a low level. An approximate total of 24,000 mi. was flown and roughly 210,000 sets of the measurements were processed for this study. Techniques of measurement and data treatment are discussed. It is shown, and discussed in detail, that the regional differences and seasonal variations of the surface albedo due to thc structure and state of the earth's surface cover are significant. The snow cover is the most important modification of the earth's surface, giving a significantly higher albedo. A quantitative relationship between the increase of surface albedo and snow cover is examined. The surface albedo measured during the flights over typical surface covers over North America, including cities, is presented. The surface covers and their textures over the North American Continent were studied mainly in terms of land use, vegetation type and phenology, soil type, and ground snow cover. The surface albedo values were estimated for various regions of the continent from the flight measurement data, considering the similarity and differences in surface structure among the regions. The resulting seasonal albedo maps of North America are presented and discussed, along with the seasonal variation of the meridional profile of thc continental surface albedo.

An Investigation of Some Synoptic Capabilities of Atmospheric “Window” Measurements from Satellite TIROS II

Several samples of infrared radiation measurements in the 8–13 micron water-vapor “window” made by TIROS II are studied in relation to conventionally observed information on pressure systems, cloudiness and temperature These cases demonstrate further the synoptic capabilities, as well as some of the limitations, of these data for cloud detection; determination of cloud-top height; and observation of spatial gradients and temporal changes in the temperature of water-, land-, and snow-covered surfaces.

Studies on Seasonal Changes in the Temperature Gradient of the Active Layer of Soil at Fort Churchill, Manitoba

Reports Canadian Defence Research Board's study, 1950-54. Experiments on rates of freeze and thaw of the active layer are described, showing the effects of surface cover, snow cover and characteristics determining the ability of the soil to conduct and absorb heat. Soil temperatures at varying depths were obtained at stations in swamp and high, dry areas of forested and non-forested localities by means of copper-constantan thermocouples and a portable potentiometer. Snow depth, water level measurements and snow temperatures were recorded for part of the time. Correlations between ambient air temperatures and soil temperatures at varying depths and with varying moisture content, ground and snow covers are presented in graphic and tabular form and discussed; also changes in snow temperature at different depths. Findings show a lag, increasing with depth and longest in relatively dry areas, of soil temperature behind ambient air temperatures; and variations in the effect of snow cover according to its hardness, moisture content and depth. The thermal gradient of the snow is affected by changes in temperature of the ambient air and of the soil, ice or water below it.

The Dielectric Properties of Ice and Snow at 3.2 Centimeters

A knowledge of the permittivity and loss tangent of snow and ice is essential in studying both radar echoes from snow-covered terrain and the attenuation of microwave energy through snowstorms. To provide this information, a program was carried out at the National Research Council of Canada to measure the permittivity and loss tangent of ice and snow, and also to determine the reflection coefficients of snow-covered surfaces, at a wavelength of 3.2 centimeters. As a result of these investigations values have been obtained for the permittivity and loss tangent of snow of varying density, temperature, and water content. Theoretical values of the reflection coefficients of snow-covered surfaces, calculated from these data, are compared with the values obtained from the direct measurement of reflections from natural snow surfaces.