| definition |
- The acoustic depth gauge (ADG) measures the distance from the gauge to the
snow. The distance to the snow surface in mm and the air temperature used to
calculate the speed of sound for the distance measurement are recorded in a
memory module at 1 hour intervals along with the hour and the Julian day of the
year. The snow accumulation is calculated by subtracting the ADG depth from the
initial distance to the snow. Figure 1 shows the June 1992 ADG record at the
time of installation. The July 1992 record shows that the snow surface may be
exposed for long time periods without significant snow accumulation. Once the
snow surface is covered with additional snow without being exposed later the
layer can be considered stored. Sampling the previously exposed surface should
give an idea of the dry fall and sampling the snow between exposed layers
should give information about the wet fall. The accumulation between previously
exposed layers may be precipitation or it could be snow trans ported to the
site. A similar approach is planned for Siple Dome and the new drilling site
near Byrd Station.
Additional information available at
http://igloo.gsfc.nasa.gov/wais/pastmeetings/abstracts99/stearns.html
[Summary provided by NASA]
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