Point Probability Distributions of Frozen Soil

Abstract

In some areas of the Pacific Northwest, frozen soils play a major role in surface runoff, soil erosion and sedimentation, but quantitative descriptions of the frequency and severity of soil frost are lacking. The temporal characteristics of frozen soil in north-central Oregon were quantified by using a soil frost simulation model to calculate the presence or absence of frozen soil over a 30-year time period. The soil frost model correctly predicted the presence or absence of soil frost 80% of the time for a 5-year field calibration period. November through March simulation results for a 30-year time period showed that frozen soil occurred every year, and the soil was frozen an average of 57 days per year. The highest incidence of frozen soil occurs during January when the soil is frozen 67% of the time followed closely by February (53%) and December (51%). The number of freeze-thaw cycles other than diurnal cycles varied from 1 to 7 per year with an average of 3 per year for the simulation period.