AIDJEX Bulletin #40 - Polar Science Center - University of Washington

algorithm removed large initial errors, but introduced 0.15 mb random errors
and significant loss of data in an unnecessary attempt to correct for diurnal
clock variations. Wind caused systematic pressure errors, but they would not
be significant for most applications. With appropriate corrections, the barometric
pressure is good to better than 0.1 mb, an error due largely to the
sampling resolution.
The external temperature sensors must be protected better than they
were during the test. The suitability of daily average external and internal
temperature measurements should be considered. If better instantaneous air
temperatures are needed, smaller sensors or some other treatment of radiation
effects will be required.
In conclusion, it is possible to obtain uniformly good measurements of
barometric pressure and temperature without resorting to field calibrations.
A summary of specific pressure accuracy requirements is given in Appendix B.
ACKNOWLEDGMENT
NASA operated the data collection system and provided the data from the
field experiment at no charge. The Naval Arctic Research Laboratory provided
field support for the test with the cooperation of the Arctic Project Office
of the Outer Continental Shelf Environmental Assessment Program. The work
was performed under the auspices of the Polar Research Center, University of
Washington, for the NOAA Data Buoy Office on contract no. 01-7-038-947.
APPENDIX A
The Digiquartz sensors are relatively insensitive to pressure (full-scale
excursions in pressure produce only a 10% change in output), which puts a
greater burden on counting accuracy. A sensor with one atmosphere full-scale
range will have a change in output of only one part in lo5 for 0.1 mb pressure
change. Accordingly, the time base will contribute 0.1 mb error for each part
in lo5 variation from the assumed clock rate. While this clock accuracy is
achieved easily with aodern laboratory equipment, it cannot be taken for granted
over a temperature range of 8OoC and a time scale of one year.
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