Snowpack temperature measurements in the Sierra: The NRCS is experimenting with digital temperature cables to measure the vertical temperature profile of the snowpack. Central Sierra Snow Lab SNOTEL and Heavenly Valley SNOTEL are each equipped with a digital temperature cable (DTC). The DTC measures temperature vertically every 8 inches (20cm). The cable hangs vertically off a tower arm and extends from -8 inches below the ground surface to 119 inches above the ground at Heavenly Valley SNOTEL and to 197 inches above the ground at CSS Lab SNOTEL. The temperature beads are intended to measure the vertical temperature profile of the snowpack to allow calculation of the snow's cold content. These measurements can help assess flooding potential leading into rain-on-snow events. Photos of the two installations are included below.
Links to snow temperature data:
- CSS Lab Digital Temperature Cable Data
- Heavenly Valley Digital Temperature Cable Data
Table Data: (last 7 days of hourly data)
Chart Data: (last 7 days of hourly data)
When viewing chart data you can mouse over traces to see sensor heights, zoom into the chart by holding down CTRL while using your mouse to draw a box around the area of interest, click titles in the legend to turn traces on/off on the chart.
Caveats about snow temperature data:
- Each bead on the cable reports temperature. The bead at -8 inches is reporting soil temperature at 8 inches below the ground. The bead at 0 inches is just above the ground. The bead at 8 inches is 8 inches above the ground and so on. Any bead above the snow surface is essentially reporting air temperature. As the snow depth increases beads get buried and report the temperature of the snow in contact with them.
- Snow depth and air temperature data are provided in the above links to help users detemine which sensors are under the snow. Temperature beads that are above the snow report data that tracks well with air temperature.
- The use of beaded temperature cables for this application is still experimental. The cable itself can act as a preferential flow path for water moving through the snowpack in the spring during snowmelt or during mid-winter rain-on-snow events. This may cause the beads to lose contact with the snow impacting the measurement. Data should be used with caution.
Snow temperature data is also being collected at other SNOTELs across the NRCS west-wide SNOTEL network.