SGP/MWR/C1 - Loss of thermal stabilization

Periodically during August and September 1995 the microwave radiometer generated error 
messages in the Site Operations Log. This error indicates that the temperature of the 
microwave hardware (specifically, the cross-coupler or "xc") exceeded its controlled 
temperature (47-52 degC) at which point it was no longer thermally stabilized and the gain was 
uncontrolled.  During these periods which typically last about 8 hours from about local noon 
until about sunset the data behave anomalously and should be considered invalid.

Specifically, the precipitable water vapor increases and the liquid water path decreases 
(and becomes SIGNIFICANTLY NEGATIVE (-0.1 mm) on clear sky days).  The RMS noise level in 
the data also increases sharply.  The 'Tkxc' field appears ONLY in the a0-level data and 
does NOT appear in either the a1 (mwrlos) or c1 (mwr5avg) files.  Therefore THESE 
ANOMALOUS VALUES HAVE BEEN INCLUDED IN THE 5-MINUTE AVERAGES.

The microwave hardware is thermally stabilized to about +/- 0.1 degC by resistive heating. 
 When the internal temperature rises above the set point the thermal stabilization of 
the instrument gain is lost. From an examination of the component temperature data, it 
appears that increasing the set point temperature to about 55 degC (328 K) would prevent a 
re-occurrence of this problem at the SGP.  The manufacturer, Radiometrics concurs that 
raising the set point will fix this problem and will not cause other problems.

Use data with caution

• Rundeck data stream - documentation not yet available

• liq
• 31tbsky
• 23tbsky
• vap

• 23tbsky
• vap
• 31tbsky
• liq

• vap
• tbsky31
• tbsky23
• liq

• Raw data stream - documentation not supported

• Raw data stream - documentation not supported

• vap
• liq
• tbsky23
• tbsky31