Monthly Snowfall Research Articles

Spatiotemporal Trends in Lake Effect and Continental Snowfall in the Laurentian Great Lakes, 1951–1980

Abstract A new raster-based monthly snowfall climatology was derived from 1951–1980 snowfall station data for the Laurentian Great Lakes. An automated methodology was used to obtain higher spatial resolution than previously obtained. The increase in resolution was attained by using all available monthly snowfall data from over 1230 stations per year combined with a monthly lime step to produce high-resolution grids. These monthly grids were combined to produce snow-year grids. Multiyear average grids were created and compared. This technique minimizes traditional problems associated with missing data and variable length station records. The three 10-year average distribution maps presented here indicate a period of increasing snowfall. Windowing of the 30 seasonal grids revealed that increasing snowfall was attributable to an increase in lake effect snowfall and not to continental snowfall. The Great Lakes drainage basin was evaluated for trends within and between monthly and seasonal average snowfall thr...

Temporal characteristics of USA snowfall 1945–1946 through to 1984–1985

AbstractThe temporal variability of USA snowfall is investigated for the period 1945–1946 through to 1984–1985 using linear trend and principal components analyses. The results of the linear trend analysis indicate that two regions of the USA evidence significant changes in monthly snowfall over the period. These areas include the Great Lakes/upper mid‐west and high plains regions of the USA. In the Great Lakes/upper mid‐west sector, positive linear trends are found in monthly snowfall totals for the mid‐winter months (December, January, February). For the high plains region, positive linear trends are found for the month of December. Principal components analysis (PCA) is used with seasonal snowfall data in order to better understand the spatial and temporal nature of seasonal snowfall variations across the USA. The PCA isolates six spatially coherent regions in which seasonal snowfall varied similarly over the 40‐year period. Only one of these regions, centred on the Great Lakes and upper mid‐west, displays any long‐term change in seasonal snowfall, a positive trend during the period 1945–1946 through to 1984–1985. These results are discussed in the context of man‐induced and natural environmental changes.

TEMPORAL STATISTICS: AN APPLICATION IN SNOWFALL CLIMATOLOGY

A method is introduced for the analysis of temporal distributions of climatic data based on a comparison of a variable's frequency distribution in the time dimension to a standard bell-shaped curve through time. The following statistics are defined using mean monthly snowfall data: the temporal mean, which is the average time for accumulation of 50% of the annual snowfall total; the temporal standard deviation, which characterizes the mean annual spread of snowfall accumulation about the mean; temporal skewness, which characterizes the symmetry of the annual snowfall distribution; temporal kurtosis, which measures the peakedness of the annual distribution; and temporal correlation, which quantifies the degree of association between two temporal distributions. Analysis of snowfall data demonstrates the utility of temporal statistics for quantifying temporal and geographic variations in a climatic variable's seasonal distribution. [Key words: snowfall, climatology, temporal statistics.]

A comparison of simulated and observed fluctuations in summertime Arctic surface albedo

The melt cycle during two Arctic summers is simulated with a dynamic‐thermodynamic sea ice model. The regional, seasonal and interannual variability of the surface albedo is compared directly with corresponding estimates derived by Robinson et al. (1986) from satellite imagery. Despite the large seasonal variability (∼0.8 to ∼0.2) of the observationally derived regional albedos, the largest error in the simulated albedo for any region or month is approximately 0.10. The model also captures much of the interannual variability of the regional albedos, which were observed to be lower in 1977 than in 1979 because of an earlier onset of melt. The component of the model's thermodynamic forcing that explains the most of the interannual variability of regional albedo (and ice thickness) is the air temperature. On the other hand, the various sensitivity tests show that the model is at least as sensitive to the specification of monthly snowfall as to the parameterization of the snow and ice albedos.

A Climatology of Mean Monthly Snowfall for the Conterminous United States: Temporal and Spatial Patterns

Mean monthly snowfall data for 216 stations across the conterminous United States were analyzed to produce a climatology that identifies statistical, spatial and intraseasonal aspects. Geographic variations in the length of the snowfall season are characterized using two statistics: the number of months of snow and the Snow Concentration Index (SCI). The annual distribution of mean monthly snowfall is also examined using harmonic analysis. Snowfall across the conterminous United States generally peaks in February; earlier snowfall maxima are found in the Great Lakes area and in the Pacific Northwest, whereas late February or March maxima occur in the western High Plains. Stations with relatively high amounts of variance explained by the second harmonic indicate 1) areas with a short snowfall season such as the southeastern United States, or 2) areas with a long snowfall season that have a tendency toward a bimodal distribution. A climatology of the changing monthly patterns of snowfall is identified through the mapping of station deviations from a national composite. This procedure produces contiguous regions that can be related to seasonal changes in the extent and positioning of the circumpolar vortex. The maps reveal that positive snowfall deviations predominate 1) in autumn in the northern and western Great Plains and the Rocky Mountains (with a full-latitude trough over the central United States and associated upslope precipitation); 2) in early winter in the Great Lakes (associated with lake-effect storms); 3) in late winter over the southern and western states (with a fully expanded circumpolar vortex); and 4) in spring in the western states (linked to seasonal changes in preferred locations of cyclogenesis and associated storm tracks).

An estimate of the role of lake effect snowstorms in the hydrology of the Lake Erie Basin

The role of lake effect snowstorms in the hydrology of the Lake Erie basin is estimated by using climatological data. By comparing monthly snowfall over areas affected by lake effect storms off Lake Erie and Lake Huron/Georgian Bay with a nearby nonaffected area, it was possible to isolate the contribution from frontal storm systems (including their augmentation due to orography) and from lake effect storm activity. These latter storms were found to contribute only 6% of the mean seasonal snowfall over the entire basin. For the snow belt southeast of Lake Erie, lake effect snowstorms provided less than 20% of the total seasonal snowfall. This percentage is low in comparison with other Great Lake snow belts because of the diminished storm activity resulting from the freezing over of Lake Erie by midwinter. The water equivalent of all snowfall over the Lake Erie basin is equivalent to a 1.07‐foot depth over the Lake Erie area. Only 0.06 foot of this depth results from lake effect snowstorm activity.

Effects of Snow Removal, Litter Removal and Soil Compaction on Soil Freezing and Thawing in a Minnesota Oak Stand

AbstractThe depths of soil freezing and thawing were measured periodically with a Veihmeyer tube in snow removed, litter removed, compacted, compacted‐snow removed, and undisturbed plots during the 1962–63 season near St. Paul, Minn. The soil was a sandy loam to a loamy sand with a high water content when the study began. Cold conditions and minimal snowfall resulted in deeply frozen soil throughout Minnesota this season. At a station near the study site, the mean monthly snowfall and mean daily air temperature were, respectively, 4 to 6 cm and 2 to 5C below normal during January and February.The removal of a snow layer 13 cm or less in depth caused deeper and more persistent soil freezing than did either litter removal or soil compaction. For several weeks, frozen soil averaged 38 cm deeper in snowless plots than in snow‐covered control plots. For about the same period, frozen soil averaged 20 cm deeper in plots without litter than in litter‐covered control plots, and 13 cm deeper in snowless compacted plots than in snowless control plots. The presence of even a shallow snowpack (13 cm) seemed to reduce the individual effects of litter removal and soil compaction on the depth of soil freezing. “Concrete” and “porous concrete” were the types of frozen soil observed in all treatments. The most significant hydrologic effect of deep freezing in snowless plots may have been the 10 additional days required for complete thawing in comparison to snow‐covered plots. However, late in the thawing period, the top of the frozen layer was 60‐cm beneath the soil surface, and it was discontinuous as indicated by complete thawing at some sample points. A discontinuous frozen layer was observed in all treatments 1 to 2 weeks before the complete disappearance of frozen soil. Thawing began earliest in plots without litter.