Characterizing Spatial and Temporal Variability of Snow Water Equivalent Using Pressure Sensors
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The goal of this study is to characterize spatial variability of snow water equivalent (SWE) at the meter scale. The study includes measurement of SWE with a new pressure sensor and use of meteorological sensor data to investigate physical properties within the snowpack that can affect sensor measurement. The new sensor, which can continuously measure a load equivalent to up to 5.5 meters of snow, is designed to be smaller and less expensive (< $1,500) than traditional pressure sensors (> $10,000). Manual snow cores and detailed snow pit analyses were performed to assess accuracy of the sensors and identify physical properties that may be related to sensor measurement error. SWE sensor response and accuracy were assessed between sensors and through comparison with bulk precipitation gage, manual SWE measurements, and snow pillows. SWE sensor readings compared favorably to other measurement methods, particularly in early and peak season. Spatial variability of SWE during the melt season of the two low-snow years during the study period confounded our ability to compare multiple sensor readings for validation. Spatial variability of SWE at study sites was calculated from sets of manual SWE measurements. The correlation length of 80 cm, determined using semi-variograms, highlights the small scale variability in SWE. Statistical resampling of manual measurements suggests that a minimum of ten manual measurements are needed to get within 10% of the spatial average of SWE. Although SWE can remain relatively stable during the melt period, this can be a result of increased density with decreasing snow depth, suggesting that simple inferences about SWE from depth measurements are not appropriate.