Addressing Bias in Snow Water Equivalent Measurement Methods Jordan French Special Acknowledgments to: Dr. Jeff Snider, UW Atmospheric Science, WyCEHG, NSF, and Snowmetrix

What is the significance of snow? Largest precipitation type in northwestern US http://travellogs.us/2009%20Logs/Wyoming%202009/09-45%20Wheatland/IMG_5649haypppp.JPG https://imagesus-ssl.homeaway.com/mda01/eea58316-8e6e-4176-b574-5d9ca4d59406.1.10/Medicine-Bow-Peak-a-winter-wonderland.jpg

Snowfall Measurement Methods Snotel Hotplate snow gauge Manual “snowboard” method Scales

Project in upstate NY Lake snow effects Discrepancy between methods

Hypotheses 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. 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: 𝑥 𝑝 = 1 𝑁 𝑁=1 10 𝑥 𝑖 𝑥 𝑝 = 1 𝑁 𝑁=1 10 𝑥 𝑖 where 𝑥 𝑖 =𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 𝑤𝑒𝑖𝑔ℎ𝑡 Standard Deviation: 𝑥 𝐴 = 1 𝑁 𝑁=1 10 (𝑥 𝑖 − 𝑥 0 ) Relative Precision: 𝜎 𝑃 𝑥

Scale 1 Scale 2

Scale 3

Weighing Accuracy Average departure from reference: 𝑥 𝐴 = 1 𝑁 𝑁=1 10 (𝑥 𝑖 − 𝑥 0 ) Standard Deviation of departure: 𝜎 𝐴 = 1 𝑁−1 𝑁=1 10 ( 𝑥 𝑖 − 𝑥 0 ) 2 where 𝑥 0 =𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑚𝑎𝑠𝑠

Scale 1 Scale 2

Scale 3

Snowfall Measurements in the Snowy Range

Snow Water Equivalent Measurement Procedure Single snow event Extract snow core with tube Determine weight of snow 𝑆𝑊𝐸= 𝑚 𝑠𝑛𝑜𝑤 𝜌 𝐻 2 𝑂 ∗( 1 𝐴 ) 𝜌= 𝑆𝑊𝐸 𝑑 ∗( 𝜌 𝐻 2 𝑂 )

Snowboard Method Results Tube 1 Tube 2 Tube 3 Snow Depth (mm) 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 http://tedmuller.us/Outdoor/Hiking/2012/2012img/Aug02/37.jpg https://www.nps.gov/romo/images/lg_melt.jpg http://geology.com/lakes-rivers-water/wyoming.shtml