Addressing Bias in Snow Water
Equivalent Measurement
Methods
Jordan French
Special Acknowledgments to:
What is the significance of snow?
Largest precipitation type in northwestern US
https://imagesus-ssl.homeaway.com/mda01/eea58316-8e6e-4176-b574-5d9ca4d59406.1.10/Medicine-Bow-Peak-a-winter-wonderland.jpg
http://travellogs.us/2009%20Logs/Wyoming%202009/09-45%20Wheatland/IMG_5649haypppp.JPG
Snowfall Measurement Methods
Snotel
Hotplate snow gauge
Manual “snowboard” method
Project in upstate NY Lake snow effects
Discrepancy between methods
Hypotheses
1. The scale measurement of weight (precision ± 0.3 %) agrees with the value of a standard weight - within measurement error - and this agreement is apparent regardless of temperature.
2. The manual method measurement of SWE compares well with the hotplate measurement of SWE.
Objective: Improved confidence in snowfall measurements is expected to result from this research
Weighing Precision
Mean: ҧ𝑥𝑝 = 1 𝑁 𝑁=1 10 𝑥𝑖 where 𝑥𝑖 = 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 𝑤𝑒𝑖𝑔ℎ𝑡 Standard Deviation: ҧ𝑥 𝐴 = 1 𝑁 𝑁=1 10 (𝑥𝑖−𝑥0) Relative Precision: 𝜎𝑃 ҧ𝑥Weighing Accuracy
Average departure from reference: ҧ𝑥 𝐴 = 1 𝑁 𝑁=1 10 (𝑥𝑖−𝑥0) Standard Deviation of departure:
𝜎𝐴 = 1 𝑁 − 1 𝑁=1 10 (𝑥𝑖 − 𝑥0)2 where 𝑥0 = 𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑚𝑎𝑠𝑠
Snow Water Equivalent Measurement
Procedure
1. Single snow event
2. Extract snow core with tube 3. Determine weight of snow
𝑆𝑊𝐸 = 𝑚𝑠𝑛𝑜𝑤Τ𝜌𝐻2𝑂 ∗ ( Τ1 𝐴) 𝜌 = 𝑆𝑊𝐸ൗ𝑑 ∗ (𝜌𝐻2𝑂)
Snowboard Method Results
Tube 1 Tube 2 Tube 3
Snow Depth (mm) 20 20 20 SWE (mm) 0.448 0.442 1.329 ρ (kg/m^3) 22.384 22.090 66.452
Conclusion
More fieldwork to be done
https://www.nps.gov/romo/images/lg_melt.jpg
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