THE CHANGING DYNAMICS OF SNOW PROCESSES IN THE MOUNTAINOUS WESTERN US

Among the effects of a changing climate at the land surface, the effects on snow are among the most evident. The phase change of falling precipitation from solid to liquid at around 0o C dictates that in a warmer climate, less snow accumulates, and more precipitation falls as rain in the winter months. Furthermore, these transitions are elevation dependent, and depend as well on a region’s climatology (for instance, mountain maritime climates are more susceptible than interior continental climates). Other changes related to climate can be associated with, for instance, changes in ablation processes, related to, for instance, changes in seasonal patterns of net radiation variations. In this talk, I will review recent work that has evaluated the magnitude of projected changes in spring snow accumulation, as well as the fraction of annual runoff in changes across the West that originates as snowmelt. I will also discuss the implications of these changes for summer low flows, and flood peaks, including the nature of observed changes over the last ~ half century, likely future changes, and the nature of uncertainties in how these changes might evolve.