PROBABILITY OF OCCURRENCE OF BLOWING SNOW

Blowing snow (snow transport) affects snow cover distribution and snow melt runoff patterns in cold, wind-swept regions. This paper uses a st atistical method to examine the occurrence of blowing snow and the met eorological conditions recorded for 16 stations on the prairies of wes tern Canada over six winters. The results show that the occurrence pro bability is highly related to wind speed, air temperature and snow age . For the same air temperature and snow age, the occurrence probabilit y increases with increasing wind speed. The probability distribution o f occurrence with respect to wind speed approximates a cumulative norm al probability distribution, depending on the mean and variance of win d speed: the location and scale parameters of the normal distribution. It was found that these two statistical parameters essentially indica te snow resistance and sensitivity to wind transport. Analysis of the probability distributions for the occurrence of blowing snow for diffe rent classes of air temperature and snow age reveals that the mean win d speed of the normal distribution generally increases with increasing air temperature and snow age, and the variance of wind speed increase s with increasing air temperature. This leads to the development of a model which first estimates the two parameters of the normal distribut ion using air temperature and snow age, and then estimates the probabi lity of the occurrence of blowing snow using wind speed and the two pa rameters with the cumulative normal probability function. Comparison o f hours of occurrence of blowing snow and of fluxes of snow transport and sublimation estimated using the model to those determined using ob servations of occurrence of blowing snow shows good agreement. The res ults of this study can be used to estimate the frequency of blowing sn ow events using standard meteorological data, to determine the snow tr ansport and snow sublimation fluxes, and to examine the effect of mete orological conditions on blowing snow processes.