Siple Dome Snow Temperatures, 1999-2001

A snow temperature profile was installed at Siple Dome at the site of the automatic weather station during January 1999. The depths of the temperature measurements are +1.00, +0.75, +0.50, +0.25, 0.00, -0.25, -0.50, -1.00, -2.00, -4.00, -7.00, and -10 m depths. The depths are nominal due to snow accumulation and installation problems below -4 m. Positive depths are above the snow at the time of installation, Two junction thermocouples are used to measure the temperature difference between adjacent levels. The voltage differences are measure by the weather station using a differential multiplexor and a high gain amplifier with high common mode rejection. The data are transmitted to the ARGOS System on board polar orbiting satellites of the NOAA series. The data are updated at 10 minute intervals and the satellites receive about two observation every hour. Past values are not transmitted because the snow temperatures usually do not change rapidly.

The data series to be presented will start 1 February 1999 and end on 31 January 2001. The data will be averaged in means for each day to form the data set for harmonic analysis of the annual cycle. The first and second harmonics will be used to compare the phase angle to the log of the temperature amplitude. This comparison will show if the heat flow in the snow is by thermal conduction. This will be carried out for the eight possible annual cycles at 90 day intervals.

The shift in the phase angles of the temperatures levels nearest the surface from the air temperature phase angle will be compared for each of the annual cycles and used to estimate the depth of the snow about the highest snow covered sensor. Accumulation estimates can be made at 0.25 m increments when the temperature sensors above the snow zero level are covered with snow. The snow temperatures will be converted to the saturation vapor pressure of ice and another set of graphs will be presented related to the possible movement of water vapor in the snow. Annual mean temperatures in the snow for Siple Dome and also GISP2 in Greenland will show that the snow temperatures can change significantly from one annual cycle to the next. The annual mean temperature in the snow is usually lower than the mean air temperature at 3 m.