Occurrence Of Snow Research Articles

Simulating Snowmelt and Soil Frost Depth by an Energy Budget Approach

The occurrence of snow and soil frost influences hydrology and, in turn, the mechanisms of soil erosion processes in cold regions. For these regions, reliably modeling the dynamics of snow accumulation and melt, and soil frost formation and melt, is necessary prior to accurately predicting runoff and erosion. Only then will methods for predicting the rates and amounts of soil erosion by water be established on a firm hydrological footing. This article examines the potential of an energy budget approach to simulate the magnitude and variations of snow and soil frost depths. It is assumed that the net sum of all energy components in the environment is consumed or compensated by water phase change occurring near or under the ground surface, such as snow melting or soil freezing and thawing. Testing indicates that this energy budget approach demonstrates promise to simulate winter hydrology and to be adapted to erosion prediction models.

Adverse-Weather Trends in the Canadian Arctic

Abstract This study provides an assessment of changes in the occurrence frequency of four types of adverse-weather (freezing precipitation, blowing snow, fog, and low ceilings) and no-weather (i.e., no precipitation or visibility obscuration) events as observed at 15 Canadian Arctic stations of good hourly weather observations for 1953–2004. The frequency time series were subjected to a homogenization procedure prior to a logistic regression–based trend analysis. The results show that the frequency of freezing precipitation has increased almost everywhere across the Canadian Arctic since 1953. Rising air temperature in the region has probably resulted in more times that the temperature is suitable for freezing precipitation. On the contrary, the frequency of blowing snow occurrence has decreased significantly in the Canadian Arctic. The decline is most significant in spring. Changes in fog and low ceiling (LC) occurrences have similar patterns and are most (least) significant in summer (autumn). Decreases were identified for both types of events in the eastern region in all seasons. In the southwest, however, the fog frequency has increased significantly in all seasons, while the LC frequency has decreased significantly in spring and summer. The regional mean rate of change in the frequency of the four types of adverse weather was estimated to be 7%–13% per decade. The frequency of no-weather events has also decreased significantly at most of the 15 sites. The decrease is most significant and extensive in autumn. Comparison with the adverse-weather trends above indicates that the decline in no-weather occurrence (i.e., increase in weather occurrence) is not the result of an increase in blowing snow or fog occurrence; it is largely the result of the increasing frequency of freezing precipitation and, most likely, other types of precipitation as well. This is consistent with the reported increases in precipitation amount and more frequent cyclone activity in the lower Canadian Arctic.

The impact of variable snow pack accumulation on a major Scottish water resource

In regions such as northern Scotland, where winter temperatures are such that the occurrence of snow is borderline under the present climate, potential changes affecting precipitation and temperature regimes may have a disproportionately large impact on snow processes and hydrological behaviour. The physical characteristics of mountainous areas in Scotland mean that the spatial variability of snowpack accumulation is high, as well as the temporal variability caused by the climate. There have been few modelling studies aimed at assessing the significance of snow resources in these areas and none that have adopted a spatially distributed approach. This paper describes the approach taken in applying a new distributed model to a headwater catchment in the Cairngorm Mountains. The results demonstrate the importance of wind on re-distributing snow to create deep accumulations in small sheltered pockets. These accumulations are shown to be important in sustaining baseflows in the rivers, long after snow has melted from the rest of the catchment. The model has also produced a first set of maps showing how predicted snow depths vary across the catchment through the winter.

Relation between Eurasian Snow Cover, Snow Depth, and the Indian Summer Monsoon: An Observational Study

Satellite-derived snow cover data for 22 yr and snow depth data for 9 yr over Eurasia have been analyzed to reexamine the possible relation of snow with the Indian summer monsoon. In contrast to the previous studies that use snow cover averaged over all of Eurasia as a single number, the frequency of occurrence of snow at each grid point over Eurasia is correlated with the Indian summer monsoon rainfall. Thus specific geographical regions over Eurasia that are responsible for the well-known inverse relationship between Eurasian snow cover and Indian monsoon rainfall are delineated. It is found, somewhat surprisingly, that western Eurasia is the only geographical region for which a significant inverse correlation exists between winter snow cover and subsequent summer monsoon rainfall. However, composites for high and low snow cover over Eurasia show spatially homogeneous large-scale patterns of snow cover and surface temperature anomalies. Winters of high and low snow cover for Eurasia are found to be associated with colder and warmer than normal temperatures, respectively, for large regions of the Eurasian continent. The inverse snow–monsoon relationship holds especially in those years when snow is anomalously high or low for both the winter as well as the consecutive spring season. Contrary to previous findings, no significant relation is found between the Himalayan seasonal snow cover and subsequent monsoon rainfall.

Mapping wet snowcovers with SAR interferometry

The capability of mapping wet snowcovers by means of Synthetic Aperture Radar (SAR) is well known. However, using only the backscattering intensity at C-band, there still remain some incertitudes regarding the effect of either rough snow surfaces or very small liquid water contents for measurements performed at small incidence angles. Since the European remote sensing (ERS) satellites usually operate at 23 incidence angle, it is important to consider these effects. This paper shows that these difficulties can be overcome using repeatpass SAR interferometry. ERS data over a part of the Netherlands and a part of Switzerland are used as illustrative examples. In the situations examined the occurrence of wet snow could not be directly observed by means of the backscattering intensity, but the use of the degree of coherence allowed an easy discrimination. The results are validated with in situ measurements.

A vegetation model for the Sayan Mountains, southern Siberia

A mountain vegetation model driven by regional climatic parameters was developed for predicting the geographic distribution of the numerous ecosystems of the Sayan Mountain system in southern Siberia. Meteorological data are drawn from normal records of monthly means. Four climatic variables were interpolated to a 10′ by 10′ grid: temperature, precipitation, vapor pressure, and cloudiness. In addition, albedo was derived by 100-m elevation classes for both windward and leeward slopes as a function of the general type of vegetation surface and the dates of snow occurrence. Ecosystems were classified using a two-dimensional climatic ordination. The first dimension was growing degree-days above a 5 °C threshold, and the second was Budyko's dryness index, which is based on annual radiation balance and annual precipitation. The patterns of predicted vegetation corresponded rather well to observed mapped vegetation. Overall κ statistics indicated agreement with observed vegetation that varied from fair at the finest resolution (10′ by 10′ cells) to good at intermediate resolution (30′ by 30′ cells and 1° by 1° cells) to very good at the coarsest resolution (2° by 2° cells). Focusing on individual vegetation classes, agreement was good to very good for each vegetation class at intermediate resolutions and very good to excellent for each vegetation class at the 2° by 2° resolution. Thus, the general location, pattern, and overall distribution of these mountain ecosystems was accurately predicted. This approach for predicting the spatial distribution of biomes was successfully applied at both the global and subcontinental scale. The successful extension of Budyko's radiation balance approach to mountainous terrain on a finer resolution regional scale indicates the generality of the approach.

Objective Guidance for 0–24-Hour and 24–48-Hour Mesoscale Forecasts of Lake-Effect Snow Using CART

Abstract Lake-effect-snow-possible (LESP) days were identified for each of 29 climatological stations in the lee of Lake Huron and Georgian Bay for the November-to-April winters of 1984–1988, using 0–24-h and 24–48-h wind and temperature forecasts from the Canadian Meteorological Center operational spectral numerical weather prediction model. Observed 24-h snow amounts on LESP days were separated into five ordered categories. A symmetric distribution centered on category 3 (>5–12.5 cm) was found for the aggregate of the 29 stations, but the distributions for individual stations peaked on category 1 (0-trace) or category 2 (>trace-5 cm). This suggests lake-effect snow occurrence, and amounts are likely to be overforecast for specific sites and small areas in forecasts issued for many public forecast regions, whose boundaries tend to be large. A recently developed nonparametric classification procedure known as “Classification and Regression Trees (CART)” was used to find decision trees that classify the ca...

Winter storm structure and melting‐induced circulations

Abstract Extensive observations were made of a winter storm that crossed eastern Canada on 10–12 March 1986 during the Canadian Atlantic Storms Program (CASP) field project. A kinematic description of the storm is established by using isentropic analyses and this description is compared with storm observations in other regions as well as with other CASP storms. The occurrence and role of snow and freezing precipitation in this storm are highlighted. It is suggested that the evolution and organization of the storm was greatly influenced by mesoscale circulations driven by melting snow.

Use of Enhanced IR/Visible Satellite Imagery to Determine Heavy Snow Areas

Abstract Interpretation techniques are established which relate heavy snow (100 mm or more in a 12 h period) areas to real-time infrared and visible geostationary satellite imagery. An initial collection of cases totaled about 75 during the period from the fall of 1979 to the spring of 1984. The main area of concern extended from the Rockies to the Appalachians. By using conventional surface and upper air data and numerical model output from the LFM-II relationships were established between heavy snow occurrences and cloud patterns in the satellite imagery. The different cloud patterns and flow regimes suggest a classification of heavy snow events into four main types: High Plains cyclogenesis, northwest and southwest flow short-wave troughs, and orographic. Each type has preferred geographical locations, common snowfall durations, storm totals, and band widths and lengths. The snowfall maximum with each storm is influenced by the strength and movement of the system and the structure of the moist layer. S...

A study of the chemical components of aerosols and snow in the Kashmir region

Atmospheric aerosols in surface air were sampled for a total period of 2 weeks, from February 25 to March 11, 1971, during the winter season, at Gulmarg and Srinagar. Snow samples were also collected on days of snow occurrence during the period. Aerosols were sampled using cascade impactor and millipore filter assembly. Samples collected through impactor were categorized into hygroscopic and non-hygroscopic nuclei while chloride, ice-forming and total nuclei were evaluated from millipore filters. Analysis of the aerosol data showed higher counts for all the nuclei at Srinagar with respect to Gulmarg. Fractions of chloride, hygroscopic and ice-forming nuclei among the total nuclei were larger at Gulmarg. Aerosol counts during the days were higher as compared to the corresponding night values. All the chemical constituents, except Cl - , gradually reduced from the initial to the end stage of the snowfall. Snow sample from Srinagar indicated higher cation concentrations. Variations of aerosols under different weather conditions have been discussed. DOI: 10.1111/j.2153-3490.1980.tb01719.x

Arctic sea ice decay simulated for a CO2-induced temperature rise

A large scale numerical time-dependent model of sea ice that takes into account the heat fluxes in and out of the ice, the seasonal occurrence of snow, and ice motions has been used in an experiment to determine the response of the Arctic Ocean ice pack to a warming of the atmosphere. The degree of warming specified is that expected for a doubling of atmospheric carbon dioxide with its associated greenhouse effect, a condition that could occur before the middle of the next century. The results of three 5-year simulations with a warmer atmosphere and varied boundary conditions were: (1) that in the face of a 5 K surface atmospheric temperature increase the ice pack disappeared completely in August and September but reformed in the central Arctic Ocean in mid fall; (2) that the simulations were moderately dependent on assumptions concerning cloud cover; and (3) that even when atmospheric temperature increases of 6–9 K were combined with an order-of-magnitude increase in the upward heat flux from the ocean, the ice still reappeared in winter. It should be noted that a year-round ice-free Arctic Ocean has apparently not existed for a million years or more.

Alkaline snowfalls in Ottawa and Winnipeg, Canada

The first snowfall of the winter 1974-75 in Ottawa, Canada revealed what is interpreted as the influence of a cement industry in the centre of the National Capital Region. Snow pH values of less than 6 were found outside the city limits. Values systematically increased to over pH 9.0 in the centre of the city. The alkaline samples contained anomalous concentrations of Ca and Mg. In 1975-76, snow samples collected in the most alkaline area of 1974-75, had normal pH values of 6 or less. Between the two collection periods, a large cement plant operation located in the centre of the 1974-75 pattern, had ceased operations. This fact, in conjunction with the Ca and Mg concentrations in the 1974-75 samples, and the occurrence of alkaline snow collected during the winters of 1975-76 and 1976-77 in an area of presently operating cement plants in Winnipeg, support the contention that the alkaline snowfall in Ottawa was related to the cement plant's former operations.

The mapping and interpretation of snow conditions in Quebec-Labrador using ESSA-9 composite minimum brightness (CMB) charts

This study is concerned with the interpretation of snow conditions using 5-day composite minimum brightness (CMB) charts which are computer products derived from digitized and rectified satellite video data. The usefulness of CMB charts is tested in the study of the areal extent and temporal variation of the snow cover over the Quebec-Labrador peninsula during the period early March to late July, 1972. Using a Densichron densitometer and a grid overlay, the spatial distribution of brightness values was analysed, and each CMB chart was reformated into a map of approximately 550 reflection values. Relationships were established between reflection values and both snow depth and recent snow occurrence, and the physiographic influences were identified. The data were used to follow temporal changes in the areal extent of the snow cover, and an attempt was made to use the data as an indicator of snow conditions.

A Search for Necessary Conditions for Heavy Snow on the East Coast

An investigation into the synoptic conditions necessary for the occurrence of heavy snow on the east coastal plain of the United States has revealed no obvious characteristic antecedent patterns either 12 or 24 hr prior to the onset of snow. The contemporaneous association of heavy snow with east coastal secondary cyclogenesis and with certain synoptic features at the 850-mb level is found to be of limited predictive value.

FORECASTING SNOW AND RAIN FOR THE NEW YORK CITY AREA USING THE METHOD OF ORDERED STATISTICS1

ABSTRACTThe occurrence of rain and snow for New York City is examined in relation to atmospheric parameters at three levels for four first order weather bureau stations. An objective forecasting guide is developed using order statistic properties. Incorporating surface and upper level data, the guide is a highly accurate forecast tool.

A Weather Singularity over the U. S. in October

A sudden increase in the probability of snow occurrence during the month of October at Denver, Colorado, had been reported. It is shown that this increase can be associated with the development of a widespread weather singularity occurring at that time of the year. The normal sea-level pressure-pattern changes derived from 40 years of data over the United States show the synoptic development of this singularity. This development leads to peculiarities in various weather elements at that time.

White Rainbow at Malvern

AN account of a white rainbow has been received from Mr. R. H. Stevens of "Rockland", Cowleigh Road, Malvern. The bow was seen at about 10.30 a.m. on November 8 after a short snowstorm, but no snow could be seen to be falling at the time of the observation. The white rainbow, also known as the 'fog-bow' or 'Ulloas Ring', is a rare phenomenon due, as in the case of the ordinary coloured rainbow, to refraction and reflexion of sunlight in falling drops of rain, but the raindrops composing the cloud must be very small—0·1 mm. or less in diameter. When this is the case, the first maxima of intensity for the different colours of the spectrum are spread out over a wider angle than with the larger drops, and are nearly coincident, the result being approximately to restore the original colour of the sunlight. The bow is only bright enough to be visible in exceptionally favourable circumstances and when the observer is near the cloud which contains the small drops. In this instance the previous occurrence of snow must be assumed to have been fortuitous, the snow probably having originated from clouds at a higher level than that of the cloud which carried the water drops.

A study of propagation over the ultra-short-wave radio link between Guernsey and England on wavelengths of 5 and 8 metres (60 and 37.5 Mc/s)

The paper presents a survey and analysis of field intensity measurements obtained during the years 1937–1939, over the Post Office radio-telephone link between Guernsey and Chaldon, England, on wavelengths of 5 and 8 m. (frequencies 60 and 37.5 Mc./s.). The path between the stations was almost entirely over sea and about 85 miles in length, of which some 36 miles was outside the optical range. The data recorded have been analysed in such a way as to illustrate the general and detailed variations in received signal strength, and the manner in which these are dependent on various atmospheric conditions.The results of the analysis have shown that while the fading of the signals was similar in type on the two wavelengths, there was a difference in the secular variation of the amount of fading on 5 and 8 m. No diurnal or seasonal variation of signal intensity was noted, nor was there any definite diurnal variation in the amount of fading. The fading observed took various forms, ranging from a rapid type in which the changes occurred more or less periodically every three or four minutes, to a slow type of variation extending over one or more hours. The latter type was usually accompanied by a high level of signal intensity interrupted at long intervals by rapid and deep fading lasting from 10 to 30 minutes. The field strength records show a marked correlation between periods of negligible fading and the existence of low atmospheric pressure conditions generally, including lack of appreciable temperature inversion. The occurrence of fog and snow has a similar effect to that due to the prevalence of low pressure.A consideration of these results and of similar data obtained by other workers leads to the conclusion that abrupt changes in temperature and water vapour gradients in the atmosphere give rise to signal variations in good weather, while the absence of these discontinuities in bad weather allows of steadier signal conditions.

The Aberdeenshire Dee

RIVER FLOW RECORDS, the private organisation directed by Capt. W. N. McClean, has just issued in brochure form (Parliament Mansions, London, S.W.I. 105. 6d.) a complete account with diagrams of the observations and readings taken for the year 1935 in connexion with the survey of the River Dee (Aberdeenshire), comprising records of water-level, flow and rainfall. The diagrams, in four sheets, exhibit in coloured outline the monthly water-levels at Cairn ton Gauge Post in 3-hourly averages, and the aggregate rainfall and run-off over a catchment area approximately of 528 square miles. The value of these monthly diagrams has been enhanced since their publication for 1934 by the inclusion of the maximum and minimum temperatures and wind at Balmoral and by the incidence of rainfall from the automatic rain gauge. Thus the occurrence of snow and the effect of temperature in increasing or diminishing the flow become clear in winter and spring months. The effect of wind is not obvious, and it appears likely that certain changes in water-level, which, locally, are attributed to strong down-stream winds, may be due to temperature.

Ice-Caves

THE occurrence of snow and ice in an old mine during the month of June, mentioned by Mr. J. Clifton Ward in his interesting paper in NATURE, vol. xi. p. 309—to the accuracy of the greater part of which I can bear personal testimony—has a more exact parallel in the Alps than “a Swiss glacier,” namely, a glacière. These remarkable caverns have been fully described by Mr. G. F. Browne in his able and pleasant work, “Ice-Caves of Switzerland and France;” and briefly by myself in “The Alpine Regions” Since the publication of that book I have seen others; and as one of these has never, I think, been described in any English work, I venture to take the opportunity of sending you a short account of it. It is in the Val d'Herens, a short distance from Evolena, on the way to the Pic d'Arzinol, and is called the Pertuis Freiss. A slip or subsidence of part of a cliff appears to have cracked the rock and opened two joints, into one of which fissures one can descend. This is about four feet wide and generally some four yards high, the floor being a little below the level of the ground outside. The crevice comes to an end in about a dozen yards. Against the slightly sloping wall of rock rested some pendent sheets of ice, whose thickness rarely appeared to exceed three inches, and irregular patches of ice lay about the floor. The temperature of the air appeared to be a little above the freezing (unfortunately, I had not a thermometer with me). It was a warm summer's day—July 23. The ice exhibited the usual prismatic structure, but the prisms seldom exceeded a third of an inch in diameter. I was informed that in winter it was choked up with snow. The other fissure also contained ice, but as it was less accessible, and seemed in no way different from the former, I did not enter it. The especial interest of this case is that it affords what I might call the most rudimentary type of a glacière; a natural ice-house, replenished every winter, and perhaps sometimes entirely cleared out during an unusually hot summer. The “Grotto” on Monte Tofana, near the Ampezzo Pass (which I have not been able to visit), is, I expect, another of this kind.