MEASUREMENTS ON NEW-FALLEN SNOW.
MCGILL UNIV MONTREAL (QUEBEC) STORMY WEATHER GROUP
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The rate of accumulation of snow at the ground has been recorded by photographing the snow surface against a wire grid. The records have provided useful data about amounts and rates of snowfall at Montreal. Of 101 snowstorms considered, half deposited less than 2 mm of water mmw. During a winter there are only half a dozen storms that deposit more than 10 mmw 4 inches of snow. Half the amount of snow in a season comes at rates of 1.2 mmwhr and less. The highest rate measured in two winters was 7.4 mmwhr over a period of one-half hour. The snow surface is continually subsiding at a rate generally less than 1 mm of snow per hour. The subsidence is due to the compacting of the snow cover presumably as the crystals become modified in their new environment. The rate of compacting of any layer in the new snow is found to be about 1 per cent per hour, independent of the snow density. Many measurements of the snowfall rate R and the average mass per crystal m have provided values of Rm, the number of snow crystals reaching unit area of the surface per unit time. A typical number is 1 per cent sq cm per sec. Over a whole seasons data, the flux is proportional to the snowfall rate. Specifically, two thirds of the measurements lie within a factor two of a locus Rmsq cm sec 1.5 R1.0 where R is in mmwhr. Author