Ground Snow Measurements: Comparisons of the Hotplate, Weighing and Manual Methods

The Yankee Environmental Systems (YES) Hotplate was developed to avoid some of the problems associated with weighing snowfall sensors. This work compares Hotplate, weighing sensor (ETI NOAH-II) and manual measurements of liquid-equivalent depth. The main field site was at low altitude in western New York; Hotplate and ETI comparisons were also made at two forested subalpine sites in southeastern Wyoming. The manual measurement (only conducted at the New York site) was derived by weighing snow cores sampled from a snow board. The two recording gauges (Hotplate and ETI) were located within 5 m of the snow board. Hotplate-derived accumulations were corrected using a wind-speed dependent catch efficiency and the ETI orifice was heated and alter shielded. Three important findings are evident from the comparisons: 1) The Yes-derived accumulations, recorded in a user-accessible file, were compared to accumulations derived using an in-house calibration and fundamental measurements (plate power, long and shortwave radiances, wind speed, and temperature). These accumulations are highly correlated (N=24; r²=0.99), but the YES-derived values are larger by 20%.  2) The in-house Hotplate accumulations are in good agreement with ETI-based accumulations but with larger variability (N=24; r²=0.88). 3) The comparison of in-house Hotplate accumulation versus manual accumulation, expressed as mm of liquid, exhibits a fitted linear relationship Y (in-house) versus  X (manual) given by Y = -0.2 (±1.4) + 0.9 (±0.1) · X (N= 20; r²=0.89).  Thus, these two methods agree within statistical uncertainty.