Atwater Study Plot, Alta, UT

This dataset includes quality assessed hourly radiation, atmospheric, and snow mass balance observation measured in situ by instrumentation permanently installed at Atwater Study Plot (ASP), a snow observation site located in Little Cottonwood Canyon, Wasatch Mountains, UT. Observation datasets are named ASP_WYyyyy_1hr, and are provided per water year as CSV files. The raw hourly dataset undergoes quality assessment and checking to filter extraneous values that are physically unreasonable, for example, negative snow depths, or positive solar radiation values at night. Data gaps, due to missing or removed values, are filled using interpolation.

ASP is approximately a quarter acre in size and located in the town of Alta on the north side of Little Cottonwood Canyon across from Alta Ski Area (40.591206^o N, 111.637685^o W; 2668 m (8752 ft)). The plot encompasses an opening in an aspen and conifer forest, near tree line, and is roped off to limit site disturbance. The instrumentation platform, which is just above 3 m in height, sits near the center of the eastern half of the site. The instrumentation mounted on the platform includes temperature and relative humidity (Vaisala hmp45c), wind speed and direction (RM Young 05103), and a four component radiometer (Hukseflux NR01) with separate measurements of incoming and outgoing solar and longwave radiation from a set of four sensors. The radiation sensor is mounted on an arm extending away from the platform, and the instrument field of views are unobstructed. Similarly, snow depth is measured off of a master stake to the west of the platform (Campbell Scientific SR50A). Data is logged on a Campbell Scientific CR1000. Precipitation is included in the dataset, but it is taken from the adjacent Alta Guard site because a precipitation gauge was not yet installed at ASP the time of dataset publication.

This dataset also includes hourly simulated snow energy balance and snowmelt datasets named ASP_WYyyyy_Snobal_1hr, provided per water year as CSV files.  The 1d snow energy balance model SNOBAL (Marks et al., 1999) is used to calculate snow energy balance and change in phase at ASP. The model represents the snowpack as two layers, with a fixed depth (25 cm) active layer, and the remainder of the snowpack. Energy exchanges are calculated in the active layer, and then energy transfer is determined for the snowpack as a whole, from which the energy available for phase changes in both layers is determined. Inputs to the model include hourly averages of net shortwave radiation, longwave irradiance, air temperature, vapor pressure, wind speed, and precipitation mass.