Light Snowfall Research Articles

An evaluation of NCEP Eta model predictions of surface energy budget and cloud properties by comparison with measured ARM data

Time‐series output from the Eta forecast model of the National Weather Service's National Centers for Environmental Prediction was evaluated by comparison with measured values for a location in Oklahoma. The measured data were drawn from the archives of the Department of Energy's Atmospheric Radiation Measurement program for the southern Great Plains site. Surface energy budget components and cloud indicators were examined for the first half of 1997. Overall, the Eta surface energy budget was found to be nearly balanced, as intended by the model physics, except for one instance when light snowfall occurred in the spring. Despite this balance, an average 50 W m−2 excess in incoming solar radiation was found. Approximately half of this excess was attributed to deficient extinction of shortwave radiation by water vapor and aerosols in the model, while the remainder appeared to be due to cloud treatment errors. The excess shortwave flux was offset by a smaller negative bias in the downwelling infrared flux and the use of slightly high albedos, in addition to errors of lesser magnitude in the latent and sensible heat fluxes. The upwelling infrared flux and ground heat flux were closer to measured values. Ambiguity in the definition of a cloud as well as measurement limitations hindered the analysis of cloud prediction. However, a rough cloud comparison indicated that the Eta model has more difficulty predicting convection than the movement of large storm systems. In addition, cirrus clouds were predicted too frequently in the winter, while low and midlevel clouds were often missed in the spring. This study demonstrates that single‐point time‐series data can be used effectively both to ascertain the quality of model output and to investigate the treatment of individual physical processes within models.

Geographical variation in the early regeneration process of Siebold's Beech (Fagus crenata BLUME) in Japan

The causes and timing of seed death in early regeneration process of Siebold's beech (Fagus crenata Blume) was studied at 15 sites along a snowfall gradient in Japan, in order to clarify why the seedling density of the species has geographic difference remarkably. Seed production did not significantly differ along the snowfall gradient. Pre-dispersal seed mortality by insect damage was higher at sites with light snowfall than at sites with heavy snowfall, but this only seemed to be a minor factor influencing the population. A large proportion of the viable nuts that fall in autumn ware killed in winter before germination. Winter mortality was much higher at sites with thin snow cover than that at sites with thick snow cover, and this factor was strongly correlated with the geographic variation of seedling regeneration probability. There was little seed mortality by winter desiccation. The main factor contributing to the geographic difference seemed to be a seed predation by rodents in winter. Deep snow cover may reduce the success of rodents finding seeds in winter. Thus the observed relationship between snowpack depth and early mortality may be due to an indirect effect through the process of seed predation.p>

Physiological tolerance of Camellia rusticana leaves to heavy snowfall environments: The effects of prolonged snow cover on evergreen leaves

Camellia rusticana is an evergreen broad‐leaved shrub found only in areas of heavy snowfall in Japan. The ecophysiological tolerance of this species to prolonged snow cover was studied in comparison with those of Camellia japonica found in areas of light snowfall. The shoots of C. rusticana and C. japonica were stored under a simulated snow cover for 1 year. During the experimental period, about 20% of the leaves of C. japonica defoliated after 90–140 days of storage and more than 80% of the leaves browned within 360 days. The proliferation of fungi was observed on all shoots of C. japonica after 200 days. In contrast, the leaves of C. rusticana showed no visible changes throughout the experimental period. The decline in the rate of soluble carbohydrate content in C. rusticana was about one‐sixth of that in C.␣japonica. The photosynthetic capacity (O2 exchange rates at saturated light and CO2 at 20°C) of C.␣japonica dropped to about half its initial value after 140 days, while that of the C. rusticana did not change even after 360 days. Under dark conditions, the stomata of C. rusticana were always closed through the experiment, but those of C. japonica were not completely closed after 90 days. The differences in stomata characteristics and the consumption rate of soluble carbohydrates under snow‐covered conditions between the two Camellia species are important factors for determining their habitat segregation by snow depth.

Adaptation of stomatal response of Camellia rusticana to a heavy snowfall environment: Winter drought and net photosynthesis

AbstractThe adaptation of Camellia rusticana, an evergreen broad‐leaved shrub found in areas of heavy snowfall in Japan, to heavy snowfall environments, and the mechanisms by which it is damaged in winter above the snow, were investigated. The stomatal response and photosynthetic characteristics of C. rusticana were compared to those of Camellia japonica found in areas of light snowfall. In field conditions, the mean net photosynthesis of C. rusticana at photon flux density (PFD) over 200 μmol m−2s−1 (Pn(>200). was 50% larger than that of C. japonica, but in both light saturated and CO2 saturated conditions, the O2 evolution rate (Pc) of C. rusticana was not different from that of C. japonica. Mean leaf conductance at PFD over 200 μmol m−2s−1 (gl(>200)) was about 100% larger than that of C. japonica in the field. The Pn(>200)) was 50% ratio of C. rusticana was 37% higher than that of C. japonica which suggests that C. rusticana's larger Pn(>200) can be explained by its larger gl(>200). When C. rusticana trees wintering underneath the snow were projected above it, the leaves of these plants showed serious drought within five days in non‐freezing conditions. Their Pc and the maximum stomatal conductance decreased by half and did not recover. The leaves of C. rusticana showed larger gl(>200) and a less sensitive stomatal response to the decrease of leaf water potential than that of C. japonica. The stomata characteristics of C. rusticana caused larger net photosynthesis than that of C. japonica during the no snow period, and caused the need for snow cover in winter as protector from winter drought.

Measurement and modelling of cloudwater deposition to a snow-covered forest canopy

Abstract Measurements are presented of the flux of cloud droplets, as a function of particle size to a forest canopy (Sitka spruce) before and after a light snowfall. The results are compared to the predivtions of the model of Slinn. Good agreement is found provided that appropriate values for the effective target diameter are chosen, both before and after the snowfall. It is shown that the snowfall results in a considerable reduction in the flux of cloud water to the forest canopy (by a factor of about 2). The snow reduces the surface roughness of the canopy but the most important effect is that it increases the effective target diameter for the droplets impacting on the tree. This effect may considerably reduce the deposition of phytotoxic chemical species to forests at high altitude where snow cover and low cloud are common in winter.

寒冬と暖冬における日本の１月の降水量・降雪量分布の比較

It is often said that heavier snowfall is obtained in relatively colder Jaunuaries. However, lighter rainfall (not snowfall) may also be obtained then, since colder air contains less water vapour.This paper compares the distribution of precipitation and snowfall in Japan obtained in both colder and warmer Januaries with that in usual ones. Six Januaries-those of 1963, 1977, 1981, 1984, 1985 and 1986-are selected as the colder Januaries, while six-1964, 1972, 1973, 1979, 1988 and 1989-are selected as the warmer ones. In both cases, the distribution of precipitation and snowfall is discussed and compared with that of usual Januaries (Figs. 3 and 4). Also the “snowfall ratio”, which is defined as the value of the monthly total depth of snowfall per total monthly precipitation, is calculated (Fig. 5). Besides, in order to assume the relationship between the synoptic conditions, the atmospheric pressure pattern in both colder and warmer Januaries is discussed (Fig. 6).In five of the six colder Januaries, lighter precipitation was usually obtained in almost whole of Japan except for the Hokuriku District (the Japan Sea side of Central Japan) and the western part of Hokkaido, both of which correspond to the landing locations of JPCZ (Japan Seapolar Airmass Convergence Zone) or the generated locations of local anticyclones (or local low-pressure areas). The value of the snowfall ratio is larger, so it can be considered that in a colder January when a heavier snowfall occures, the precipitation usually obtained as rainfall is obtained as snowfall. The value of atmospheric pressure is not always smaller, but a steeper pressure gradient is found. However, in 1963 January, much heavier precipitation was obtained on the Japan Sea side and only lighter precipitation on the Pacific Ocean side. The value of the monthly mean atmospheric pressure was much smaller. Therefore, January 1963 must be considered as an abnormal case.In five of the six warmer Januaries, heavier precipitation was obtained on the Pacific Ocean side and lighter precipitation on the Japan Sea side, especially the Hokuriku District and the western part of Hokkaido; in 1988 lighter precipitation was obtained in the whole area of Japan. The value of the snowfall ratio was usually smaller, so it can be considered that the lighter snowfall in the warmer Januaries is the result of both lighter precipitation in itself and the rainfall usually obtained as snowfall. The value of monthly mean atmospheric pressure is usually larger, and gentler pressure gradient is found.This paper emphasizes the general features both in the colder Januaries and in the warmer ones. However some difference is found among both the colder and the warmer Januaries. And these general features do not always fit with Hokkaido or the Pacific Ocean side of Northeast Japan. These problems must be given further consideration.

The Magic of "Old Christmas"

The Magic of "Old Christmas"

Snow Accumulation and Oxygen-Isotope Records at the Law Dome Summit, Antarctica (Abstract)

At the summit of Law Dome (66°44′S, 112°50′E) the annual snow accumulation is equivalent to 0.7 m of water, and seasonal cycles of oxygen-isotope ratio are preserved clearly in the firn. Isotope-ratio measurements on three 28 m deep ice cores taken 15 m apart near the summit show that although annual layer thicknesses are well correlated between the cores, the actual isotope values (even when averaged over several years’ accumulation) are poorly correlated. Since the three sites must obviously receive the same precipitation, the differences in isotope ratio imply that the amounts of the precipitation retained as accumulation from individual snow-falls throughout the year must vary. The large seasonal variation in isotope ratio then easily accounts for the offsets. In the Law Dome region, precipitation occurs mainly as a result of cyclonic activity in spring, winter and autumn. The stronger winds experienced at these times cause the snow to be formed into large dunes, which are the stable (although moving) surface configuration under these conditions. The movement of dunes by erosion on one face and deposition on the other causes the snow in them to be well mixed. Isotope measurements on a 0.7 m high dune on the inland ice cap showed that it was composed of “winter” snow, with an average isotope value of −28.2% and a range of only 1%. The harder underlying snow had values which varied between −24.2 and −27.4%. During periods of relatively calm or warm conditions the dunes become consolidated and their movement is greatly reduced. Further snow-falls then do not add accumulation to the top and up-wind side of the dunes but tend to fill them in on the down-wind side. In particular it is observed that for Law Dome the surface profile is quite rough in winter and spring, but the more gentle winds and light snow-falls experienced in summer produce a very smooth surface at the beginning of autumn, with all the surface hollows filled in. The ice-core isotope profiles confirm the evenness of the summer accumulation, compared to that of winter. Correlation coefficients are typically 0.26 for the winter minima and 0.65 for the summer peak in isotope ratio. This means that somewhat shorter averaging times can be used when compiling “climatic” records from isotope profiles if only the “summer” isotope values are used. This is useful in comparison of isotopic and meteorological data when only a limited time span is available. Apart from the short-term effects, which can be reduced as desired by longer averaging periods, these core studies also demonstrate how any process which can modulate the precipitation or accumulation will also affect the isotopic composition of the accumulated snow.

Snow Accumulation and Oxygen-Isotope Records at the Law Dome Summit, Antarctica (Abstract)

At the summit of Law Dome (66°44′S, 112°50′E) the annual snow accumulation is equivalent to 0.7 m of water, and seasonal cycles of oxygen-isotope ratio are preserved clearly in the firn. Isotope-ratio measurements on three 28 m deep ice cores taken 15 m apart near the summit show that although annual layer thicknesses are well correlated between the cores, the actual isotope values (even when averaged over several years’ accumulation) are poorly correlated.Since the three sites must obviously receive the same precipitation, the differences in isotope ratio imply that the amounts of the precipitation retained as accumulation from individual snow-falls throughout the year must vary. The large seasonal variation in isotope ratio then easily accounts for the offsets.In the Law Dome region, precipitation occurs mainly as a result of cyclonic activity in spring, winter and autumn. The stronger winds experienced at these times cause the snow to be formed into large dunes, which are the stable (although moving) surface configuration under these conditions. The movement of dunes by erosion on one face and deposition on the other causes the snow in them to be well mixed. Isotope measurements on a 0.7 m high dune on the inland ice cap showed that it was composed of “winter” snow, with an average isotope value of −28.2% and a range of only 1%. The harder underlying snow had values which varied between −24.2 and −27.4%.During periods of relatively calm or warm conditions the dunes become consolidated and their movement is greatly reduced. Further snow-falls then do not add accumulation to the top and up-wind side of the dunes but tend to fill them in on the down-wind side. In particular it is observed that for Law Dome the surface profile is quite rough in winter and spring, but the more gentle winds and light snow-falls experienced in summer produce a very smooth surface at the beginning of autumn, with all the surface hollows filled in.The ice-core isotope profiles confirm the evenness of the summer accumulation, compared to that of winter. Correlation coefficients are typically 0.26 for the winter minima and 0.65 for the summer peak in isotope ratio. This means that somewhat shorter averaging times can be used when compiling “climatic” records from isotope profiles if only the “summer” isotope values are used. This is useful in comparison of isotopic and meteorological data when only a limited time span is available.Apart from the short-term effects, which can be reduced as desired by longer averaging periods, these core studies also demonstrate how any process which can modulate the precipitation or accumulation will also affect the isotopic composition of the accumulated snow.

Multiple Remote Sensor Observations of Supercooled Liquid Water in a Winter Storm at Beaver, Utah

Abstract The temporal and spatial distribution of cloud liquid water in a winter storm from the 1983 Utah/NOAA Cooperative Weather Modification Program is characterized using remote sensing observations. The remote sensors, located at a mountain-base site near Beaver, Utah, consisted of a dual-channel microwave radiometer operated in an azimuthal scanning mode, and a polarization lidar and Ku-band radar both operated in the vertically pointing mode. The cloud system was associated with the passage of a weak cold front and produced only light snowfall across the barrier network of precipitation gages. Although the amounts of supercooled water detected radiometrically varied considerably during the storm, liquid water depths were consistently enhanced in the direction of the barrier. The spatial distribution of liquid water was observed to undergo a transition from a primarily orographic distribution to a more area-wide pattern immediately behind the front, and then became convective as the storm dissipated...

Wavelength-dependent extinction by falling snow

Wavelength-dependent extinction in the visible and infrared regions of the electromagnetic spectrum has been observed during studies of transmission through falling snow. The wavelength dependence was particularly noticeable during periods of light snowfall. Particles comparable in size to the wavelengths were also present during these periods. These particles were assumed to be water droplets, and their extinction cross-sections were determined from Mie scattering calculations. The calculations suggest that these particles were responsible for the wavelength-dependent extinction observed during snowfall.

Snow-cover area vs. snowmelt runoff relation and its dependence on geomorphology — A study from the Beas catchment (Himalayas, India)

Snowmelt may substantially contribute to the overall discharge of a river and hence is the importance of estimating snowmelt runoff. The River Beas, in the northwestern part of India, was chosen to study the relation between snow-cover area and snowmelt runoff. Snow-cover area was mapped from the LANDSAT images for a number of years in various subcatchments. The river discharge, excess over the baseflow, in days of non-concurrent rain-precipitation, was computed which could be attributed to snowmelt alone. The snow-cover area and the subsequent snowmelt runoff in various subcatchments are found to be well correlated. It is interpreted that there have been years of uniformly heavier and lighter snowfall all over the basin and the snowmelt discharges have consequently systematically varied. For a particular subcatchment, the relationship between snow-cover area and snowmelt runoff seems to be independent of geographic factors like solar illumination, catchment orientation and relative location. On the other hand, it appears to depend on geomorphical factors such as size of the subcatchment, permanent snow-cover area, average altitude, lithology and stream order. Hence, it is considered that, for each type of geomorphical subcatchment, a different empirical relation should exist between snow-cover area and snowmelt runoff.

Winter avalanche activity and weather in a Canterbury alpine basin

Abstract Weather, snow conditions, and avalanche activity for a four-month winter period in 1977 are described for Porter Heights Skifield in the Craigieburn Range, South Island, New Zealand. They are analysed to assess the origin of a large, climax-type slab avalanche event in spring. Depth hoar, which formed early in the winter, and light snowfalls produced an unstable snowpack which failed after spring warming. Other weakening processes in the snowpack are outlined. Ski areas with potential for avalanches should be monitored daily for weather observations and hazard assessments, and snowpits dug weekly throughout the winter.

Satellite Detection of an Extremely Light Snowfall in Arizona

Abstract Estimates of snow cover area (SCA) from analyses of operational environmental satellite data have been produced since 1974. Daily, and even half hourly, images monitor changes in the SCA where continuous surveillance of the snowpack is necessary to accurately predict runoff and flood potential. A case of rapid melt of an extensive, but shallow, snow cover in Arizona is examined.

The Wintertime Arctic Front and Its Effect on Fairbanks, Alaska

Abstract Surface and upper air data for November 1974–February 1975 were examined in order to determine a method to locate and predict the movement of the wintertime arctic front over Alaska. Ten cases each of the front passing north and south over Fairbanks were studied, Frontal effects an Fairbanks were noted and methods to forecast the timing of the frontal passage at Fairbanks were determined. Movement of the arctic front over interior Alaska was found to be directly related to the location and movement of large low-pressure systems in the Gulf of Alaska. Only very light snowfall accompanied the front as it passed northward over Fairbanks. However, southward passage of the front accounted for 77% of the Fairbanks snowfall during the four mouth period. A marked temperature and moisture difference was evident between the two air masses separated by the arctic front. Periods of extremely low temperatures with clear skies and ice fog were observed when the front remained south of Fairbanks for several day...

Three‐dimensional air motion measured in snow

In this letter, we present the results of a method that uses two Doppler radars to observe the three‐dimensional wind field during light snowfall. These radars are designed to scan in a series of tilted planes, passing through the two radar positions. From the mean Doppler shifts in the frequency spectra we can determine average radial velocities within the pulse volumes. Since the two radars do not observe the same volume increments at the same time, spatial interpolation is needed before the radial velocities can be combined into a two‐dimensional velocity field at a set of common coordinates within each plane. The estimated terminal fall velocity of the snow is subtracted from the particle velocity to obtain the true air motion in the plane. The air motion component normal to the plane is obtained by integrating the equation of continuity in cylindrical coordinates starting with the surface boundary condition at the plane of zero elevation. The velocity field in the common planes scanned by the radars is then transformed into a rectangular coordinate system with one axis oriented parallel to the average wind direction. After the mean wind field is removed from the results, a well organized “eddy” wind field is evident.

Reproductive Biology of White-Tailed Deer in Manitoba

This study is based on 159 female white-tailed deer (Odocoileus virginianus) collected during the winters of 1961, 1962, and 1963 from, in order of decreasing habitat quality, the Turtle Mountain, Duck Mountain, and Whiteshell areas of Manitoba. Conception rates were high for adults and yearlings but relatively low for fawns. Ovulation rates and average numbers of fetuses per pregnant doe were high for adults from all areas but the ovulation rate was significantly higher for adults from Turtle Mountain. Both rates were high for yearlings from Turtle Mountain but relatively low for yearlings from the Whiteshell and Duck Mountain. Considering all age-groups, fertility was highest in Turtle Mountain, followed by Duck Mountain, and lowest in the Whiteshell. The rate of ova loss among adult does from Turtle Mountain was significantly higher than among adults from the other areas. This may be due, indirectly, to flushing. Kidney fat indices showed that deer from all areas lost condition at the same rate during winter. A general comparison of winter environment between the Whiteshell, which was closed to hunting, and the Upper Peninsula of Michigan indicates that lower temperatures in the Whiteshell cause deer there to suffer more from malnutrition during average winters than do deer in the Upper Peninsula and hence to have relatively higher numbers of stillbirths and postnatal losses of fawns. Lighter snowfall in the Whiteshell allows deer to cover more of their summer range in winter than do Upper Peninsula deer, thus helping to explain why over-utilization of browse in the Whiteshell is not the serious problem it is in the Upper Peninsula. Winter weather appears to be sufficient to prevent deer irruptions in the Whiteshell and to hold maximum density well below that reached in the Upper Peninsula. It is postulated that similar controls function in the rest of Manitoba. White-tailed deer in Manitoba have a high level of fertility but densities are relatively low compared with most good deer areas in the United States. Irruptions, characterized by severely decreased size and fertility; the formation of browse lines; prevention of forest regeneration; and eventual mass die-offs, do not occur in Manitoba, apparently because winter environmental conditions during average years result in over-winter losses and an unusually high percentage of stillbirths and postnatal losses of fawns. Consequently the average annual increment is relatively small. This study was undertaken in 1960 with the support of the Manitoba Wildlife Branch and was completed in fulfillment of research requirements for a M.Sc. degree from the University of Alberta. I wish to express sincere gratitude to Eugene F. Bossenmaier, Chief Biologist, Manitoba Wildlife Branch, for suggesting the study initially, for his continued advice and encouragement, and for his helpful criticisms of this manuscript. Sincere gratitude is also extended to Dr. W. A. Fuller and to Dr. J. C. Holmes, Department of Zoology, University of Alberta, for their guidance during the final year of the study and for their criticisms of the manuscript. Dr. W. G. E. Evans, Department of Entomology, University of Alberta, also gave helpful criticisms. Special thanks are extended to Conservation Officers of the Manitoba Department of Mines and Natural Resources who collected specimens for the study. Appreciation is expressed to Dr. G. I. Paul, Department of Statistics, University of Manitoba, for his advice on statistical analysis of the data. I also wish to thank L. J. Verme of the Michigan Department of Conservation for his comments on the manuscript.

降雪による地表電場の擾乱について

Simultaneous observation of surface electric field, charge on snow particles, rate of snowfall, crystal type of snow crystals was made during snowfall in four winter seasons from 1956 to 1960 in Sapporo. Various patterns of the surface electric field occurred during the observation.From the observational results obtained, the following conclusions were obtained.1. In the case of quiet and light snowfall from higher clouds of layer type, non-rimed snow crystals are charged negatively by a mechanism similar to Wilson's induction mechanism, and the so called inverse relation between positive surface electric field and negative charge on falling snow crystals is observed.2. In the case of heavy snowfall from such as nimbocumulus clouds, graupel or rimed snow particles are charged positively at temperature higher than -10°C by friction with non-rimed snow crystals which are charged negatively. A negative surface electric field is formed by the removement of positive charge on falling graupel from cloud layer, and thus inverse relation (positive snowfall under negative surface electric field) is observed.3. In the case of showery snowfall, negative and positive sharp peaks occur in the electric field record. These peaks are produced by the change of local space charge near the observation point. The mechanism of charge generation is the same as in 2.

The Effect of Suspended Ice Crystals on Radiative Cooling

Two periods of very low (below −40C) surface temperature of Fairbanks, Alaska, were studied in detail as part of ice fog investigations during the 1961–1962 winter. The observed cooling rates from teh snow surface up to 3000 m were to large to be satisfactorily explained by advection and/or by radiative heat losses from the air and from the snow surface. The excess is shown to be due to radiation from ice crystals suspended in air. The ice crystals, formed by overall cooling of the air, act as heat sinks. It is proposed that heat flows from the air to the crystals and is radiated away. This process results in strong temperature gradients in the air immediately adjacent to the crystals. It may also account for the fact that humidity measurements show less than saturation values during occurrences of ice fog, light snowfall or “diamond dust” crystal displays. The air temperature values used in determining humidity pertain to ambient air between the ice crystals, whereas the air in contact with crystals has a lower temperature and is saturated with respect to ice.

The relationship een the ear development in autumn and the sowing time in barley varieties

The sowing time of wheat and barley in heavy snowfall regions is early and the progress of the ear development in barley varietes in autumn is not always correlated with the degree of spring habit. In the present study, 38 varieties of barley were sown several times in autumn and the degree of the ear development was investigated before the continuous snow-cover. These barley varieties were classified into 6 groups based on the degree of provisionally called "early sown growth habit". On the whole, the varieties which have very low or high "early sown growth habit" almost show very high or low spring growth habit respectively, but some varieties which have I -V degree of growth habit belong to the groups of II and III "early sown growth habit" and these two growth habits are not always correlated to each other. Hence, they are recognized as different characteristics. The spring growth habit, examined by sowing several times in spring, is important in the light snowfall regions, because barley plants are damaged by cold in spring, but the "early sown growth habit", examined by sowing sevaral times in autumn, , is more important from the practical point of view in the heavy snowfall regions, because the cold and snow damage is related to the growth of barley in autumn and early winter. The "early sown growth habit" is to be effectively utilized in the breeding: of the barley varieties in heavy snowfall regions.