Snow temperature profiles in the Central Sierra Nevada

The temperature profile and cold content of a Sierra Nevada snowpack are significant indicators of it's potential response to environmental stimuli. An analysis of more than 2200 daily snow temperature profiles recorded at the U.S. Forest Service's Central Sierra Snow Laboratory in northern California identified those with marked subzero deviations and calculated temperature deviation frequencies. An anisothermal snow profile was defined and 31 cases were identified. January and February showed the highest proportion of anisothermal events and the largest temperature deviations while April and May showed the lowest proportion of events and the smallest deviations. Deep snowfalls produced most of the anisothermal profiles, but cold air and negative net radiation also created anisothermal profiles. Six significant rain-on-snow storms were identified and characterized. The rain reduced the snowpack's cold content and warmed interior snow temperatures to near 0 degrees C. The reduction in cold content was not uniform or proportional to rainfall depth.