Snow ablation processes and associated atmospheric conditions in a high-elevation semi-arid basin of Western Canada




Jackson, Scott Isaac

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Snow surface energy balance was studied along an elevational gradient and under varying forest cover types during the ablation season of 2007 in the Coldstream Basin, Okanagan, British Columbia, Canada. During the snowmelt period, 1-4% of the peak annual snow-water equivalent (SWE) was lost to sublimation in open sites – averaging 0.4 mm d-1. Melt and sublimation rates increased significantly with elevation, and were higher and more variable in the open sites than under forest canopies. Melt rates were driven almost entirely by sensible heat fluxes and exceeded 30 mm d-1 during large-scale advection events. The melt and sublimation processes observed at the snow surface were significantly linked to conditions in the atmospheric boundary layer. From these linkages, a proxy record of historical ablation season energy fluxes for the period 1972-2007 was created. Significant trends towards earlier dates of snowmelt and freshet onset were detected, as was a trend towards increasing ablation-season temperatures at the 850 mb height. Significant correlations between estimated historical ablation-season melt and sublimation and the regionally dominant teleconnection indices were also found. This study significantly advances the understanding of ablation season snow-surface energy exchanges, and the links to the driving atmospheric conditions in the Okanagan Basin.



snow energy balance, Okanagan Basin, SNTHERM, Atmospheric boundary layer, trends, teleconnections