Atmospheric ice ablation processes on Mt Equinox, Vermont, USA

The focus of atmospheric icing modeling has been on the accretion of rime and glaze. However, deposition and ablation together determine ice loads because ice persists after it is deposited, and residual ice often remains on structures, contributing to load when later ice accretion occurs. The goal of this study is to identify local and synoptic-scale weather conditions associated with rime and glaze ablation. A total of 77 ablation periods were recorded by time-lapse video for two winters on Mt Equinox, VT, USA. Weather information was acquired from on-site measurements, radiosondes and synoptic charts. Sublimation was the slowest process, whereas melt and mechanical ablation events were the most rapid, lasting less than 5 h. Ablation occurred principally during daylight hours. Wind speeds were similar and slowest during sublimation and melt, with sublimation occurring primarily in westerly winds, and melt occurring within southerly winds. Sublimation air temperatures and relative humidities were lowest, with medians of −11°C and 57%, respectively. In general, melt is most frequent as storms approach, and sublimation is most common as storms depart.