3.2 Meteorological conditions
The University of Saskatchewan had previously installed six automatic
weather stations (AWS) in the study catchment. In this work, AWS1
located in the meadow by the outlet springs was used (2084 m.a.s.l.). It
measured cumulative precipitation (Geonor, T-200B, with Alter wind
shield), air temperature and relative humidity (Rotronic, HC2-S3),
shortwave and longwave radiation (Kipp & Zonen, CNR4) and wind speed
(R. M. Young, 05103).
Precipitation phase was determined using an air temperature threshold of
0 °C (Marks, Winstral. Reba, Pomeroy, & Kumar, 2013). Below 0 °C
precipitation was classified as snow and above 0 °C as rain. However,
since the threshold is site specific (Marks et al., 2013) a time-lapse
camera (Wingscapes, TimelapseCam) was used to confirm the
classification. The camera was set up by the outlet springs to take
photos at 5-minute intervals. The images were then visually inspected to
see if snowfall was occurring or if it had accumulated on the ground.
This crude method assumes that snowfall does not melt within the
5-minute window, prior to image capture. Furthermore, when snowfall
occurred at night, we assume that melt did not occur until after
sunrise, due to low air temperatures. This method was suitable for our
purpose of qualitatively distinguishing between liquid and solid
precipitation.