DQRID : D931115.3
Start DateStart TimeEnd DateEnd Time Data Quality Metric
09/22/1993163011/03/19931730Suspect
more
Subject:
SGP/EBBR/E8 - Drop in atmospheric pressure
DataStreams:sgp30ebbrE8.b1, sgp15ebbrE8.b1, sgp5ebbrE8.b1
Description:
Beginning September 22, 1993, the atmospheric pressure sensor at the E8
EBBR began showing drops of as much as 5 kPa for about half a day.  These
could be easily seen in comparisons with the SMOS pressure sensor.  The
drops were diurnal and occurred during daytime, at the same time as other
quantities such as temperature, net radiation, and battery voltage were at
the highest levels of the day.  It is unclear what exactly caused this
situation.  Replacement of the Campbell multiplexer to which the pressure
sensor was connected caused the problem to go away.  The same multiplexer was
then used as a replacement for the other multiplexer in the E8 EBBR and has not
shown any odd behavior on the channel that previously served the pressure
sensor.  My conclusion is that there was poor electronic contact of the
pressure sensor to the multiplexer.

Affected pressure data can only be easily seen by comparison with SMOS
pressure data.  No EBBR data other than pressure is affected by the
pressure problem; calculations of specific heat at constant pressure (which
includes the term 1/(p-vp)) times other terms (including p-.378*vp) result in
a very small error in the resulting Bowen Ratio.  For example; assume a common
vapor pressure (vp) of 2.0 kPa, a common atmospheric pressure of 97.0
kPa, and a corrupted atmospheric pressure of 92.0 kPa.

       Uncorrupted                               Corrupted

   (97.0-.378*2.0)/(97.0-2.0) = 1.0131   (92.0-.378*2.0)/(92.0-2.0) = 1.0138

   1.0138/1.0131 = 1.00069  or  0.069% increase in the Bowen Ratio as a
                                       result of the corruption

Therefore, no correction to the quantities calculated using pressure is
warranted.
Suggestions: 
This DQR was originally PIF No. P931115.3
Measurements:sgp5ebbrE8.b1:
  • vapor_pressure_top
  • atmos_pressure
  • vapor_pressure_bottom
more
sgp15ebbrE8.b1:
  • atmos_pressure_mv
more
sgp30ebbrE8.b1:
  • vapor_pressure_top
  • vapor_pressure_bottom
  • atmos_pressure
more

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