SnowEx 2021 was a continuation of the Time Series (TS) campaign from SnowEx 2020 and included measurements at a subset of the sites from the 2020 campaign in Idaho, Utah, and Colorado, as well as an additional prairie site in central Montana. Baseline measurements began in December of 2020 and extended into April 2021 for most sites, providing observations of seasonal melt in some cases.
SnowEx 2021 snow pit measurements were central to the ground sampling strategy and matched the experiment design from the 2020 campaign. However, the interval board sampling, or weekly measurements of new snowfall and SWE, expanded at most locations. In 2020 most interval boards were co-located with a snow pit, while for 2021 most sites distributed an array of 5-8 boards to sample a range of elevations and aspects. Interval boards are an important ground validation observation to pair with the airborne UAVSAR data. Unused flight hours from SnowEx 2020 (due to the Covid-19 pandemic) were applied to weekly observations of 2021 TS sites. The SnowEx 2021 TS campaign also included albedo measurements taken in Colorado using AVIRIS-NG, a visible/infrared imaging spectrometer.