No abstract

ABSTRACT. Snow sublimation is a fundamental process that affects the snow crystal structure and is important for ice-core interpretation, remote sensing, snow hydrology and chemical processes in snow. Prior studies have shown that sublimation can change the isotopic content of the remaining snow; these studies have inferred sublimation rates using field data, and were unable to control many of the environmental parameters that determine sublimation rate (e.g. temperature, relative humidity, snow microstructure). We present sublimation rate measurements on snow samples in the laboratory, where we have controlled many of these parameters simultaneously. We use the same experimental apparatus to determine sublimation rate, investigate the isotopic effects of sublimation, and study the isotopic exchange between vapor and solid. Our results suggest that pore spaces in snow are almost always at saturation vapor pressure; undersaturation may be possible in large pore spaces or in regions of rapid interstitial airflow. We present a revised formulation for determining the mass-transfer coefficient for snow as a linear function of Reynolds number (h m ¼ 0.566Re + 0.075), estimate the fractionation coefficient for sublimating snow, and provide evidence for isotopic exchange between vapor and solid.

In early January 2022, the Paxton Siphon, owned and operated by the Nebraska Public Power District, filled with frazil ice creating a blockage that resulted in a rapid upstream stage rise for the Sutherland Canal. An event of this type has never happened in the over 80 years of operating the Paxton Siphon. An analysis of the available weather and canal data suggests a rapid air temperature change resulted in the water becoming supercooled, which combined with the moderately low flows in the canal resulted in an anomalous frazil ice formation event. To address this issue for future cold-weather events, a water-temperature model was developed using the Hydrologic Engineering Center’s River Analysis System and can be used to determine the spatial extents of the supercooling event using forecasted weather information. In addition, we developed a heat-exchange forecast tool that can be used operationally to screen for potential frazil ice formation periods with a 1-week outlook period.

The Ririe Dam and Reservoir project is located on Willow Creek near Idaho Falls, Idaho, and is important for flood risk reduction and water supply. The current operating criteria is based on fully storing a large winter runoff event. These winter runoff events are generally from large storm events, termed atmospheric rivers, which produce substantial precipitation. In addition to the precipitation, enhanced runoff is produced due to frozen soil and snowmelt. However, the need for additional water supply by local stakeholders has prompted the U.S. Army Corps of Engineers to seek to better understand the current level of flood risk reduction provided by Ririe Dam and Reservoir. Flood risk analysis using hydrologic modeling software requires quantification of the probability for all of the hydrometeorologic inputs. Our study develops the precipitation, SWE, and frozen ground probabilities that are required for the hydrologic modeling necessary to quantify the current winter flood risk.