Snowpack Measurements From Underground. John Wahr and Judah Levine Department of Physics University of Colorado. The Experiment. Put a superconducting gravity meter in the mine to monitor changes in gravity.
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Snowpack Measurements From Underground
John Wahr and Judah Levine
Department of Physics
University of Colorado
Put a superconducting gravity meter in the mine to monitor changes in gravity.
Use those changes to monitor changes in the mass of water and snow up at the surface.
Superconducting gravitymeter, manufactured by GWR Instruments in San Diego. It measures g.
A superconducting ball is levitated in a magnetic field. Electrostatic forces are applied to keep the ball centered when g changes. The meter outputs voltage.
NOAA is presently operating a meter in Boulder.
Mean value of g = 980 gals
All data analyzed by Doug Robertson (NOAA).
Red: gravitational effects of atmosphere (computed using atmospheric pressure data).
Accuracies at quiet sites are better than 1 µgal for short averaging times.
A change in mass vertically above or below the meter, would cause a change in gravity.
We will use the gravity data to estimate changes in the mass of water & snow up at the surface.
We have no vertical resolution: we see the sum of snow mass, soil moisture, and ground water.
We obtain results averaged over the region above the meter, rather than at a single point.
Mass sensitivity (assumes flat topography)
Gravity signal at 1500 m depth, from 3 cm of water spread over a disc.
Cost: $450,000 new. Or, NOAA instrument might be available for no cost in short term, though would eventually require $50,000 to restore computer & data acquisition system.