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Item A Long-Term Micrometeorological and Hydrological Dataset Across an Elevation Gradient in Sagehen Creek, Sierra Nevada, California(University of Nevada Reno, 2018) Petersky, Rose S.; Harpold, Adrian A.We compile and release ~55 years of daily and ~20 years of hourly Micrometeorological and hydrological data from Sagehen Creek a 28 km〖^2〗 watershed with observation sites spanning 1771 to 2670 m. A USGS gauging station measures streamflow at the catchment outlet. There are three Snow Telemetry (SNOTEL) stations: Independence Camp(2128 m), Independence Creek (1962 m) and Independence Lake (2541 m) that measure hourly precipitation, temperature, soil moisture (at 5, 20, and 50 cm), as well as daily snow water equivalent (SWE) and snow depth. A new method was used to estimate hourly precipitation data using quality controlled daily totals. A NOAA cooperative observer (COOP) station measures daily precipitation, temperature, SWE, and snow depth from 1953-1997 and then measures hourly precipitation, temperature, SWE, and snow depth, relative humidity, and solar radiation from 2001 through 2017 2001-present. There are an additional three towers with data beginning in 2009 measuring snow depth, SWE, solar radiation, barometric pressure, precipitation, relative humidity, and temperature: Tower 1 (1934m), Tower 3 (2114 m), and Tower 4 (2350 m). Wind speed, temperature, and relative humidity measured at 7.6 and 30.5 m at each site. Data from all stations were checked for poor QA/QC and substantial and sophisticated gap-filling techniques were deployed. This dataset holds potential for improving understanding of orographic processes and their implications for streamflow generation in a groundwater-dominated watershed.Item Now You See It Now You Don’t: A Case Study of Ephemeral Snowpacks in the Great Basin U.S.A.(2018-04-27) Petersky, Rose S.; Harpold, Adrian A.Ephemeral snowpacks, or those that routinely experience accumulation and ablation at the same time and persist for <60 days, are challenging to observe and model. Using 328 site years from the Great Basin, we show that ephemeral snowmelt delivers water earlier than seasonal snowmelt. For example, we found that day of peak soil moisture preceded day of last snowmelt in the Great Basin by 79 days for shallow soil moisture in ephemeral snowmelt compared to 5 days for seasonal snowmelt. To understand Great Basin snow distribution, we used moderate resolution imaging spectroradiometer (MODIS) and Snow Data Assimilation System (SNODAS) data from water years 2005-2014 to map snow extent. During this time period snowpack was highly variable. The maximum seasonal snow cover was 64 % in 2010 and the minimum was 24 % in 2014. We found that elevation had a strong control on snow ephemerality, and nearly all snowpacks over 2500 m were seasonal. Snowpacks were more likely to be ephemeral on south facing slopes than north facing slopes at elevations above 2500 m. Additionally, we used SNODAS-derived estimates of solid and liquid precipitation, melt, sublimation, and blowing snow sublimation to define snow ephemerality mechanisms. In warm years, the Great Basin shifts to ephemerally dominant as the rain-snow transition increases in elevation. Given that snow ephemerality is expected to increase as a consequence of climate change, we put forward several challenges and recommendations to bolster physics based modeling of ephemeral snow such as better metrics for snow ephemerality and more ground-based observations.