DQRID : D070124.2
Start DateStart TimeEnd DateEnd Time Data Quality Metric
03/01/2005000009/14/20052359Does not affect quality
more
Subject:
PYE/SKYRAD/M1 - Datalogger program error affected downwelling longwave
DataStreams:pyeskyrad60sM1.b1, pyeskyrad20sM1.a0
Description:
The excitation delays used in measuring the PIR1 case thermistor, "Case1", and the PIR2 
dome thermistor, "Dome2", were discovered to have been incorrectly set to 0 in the Skyrad 
datalogger program when the new CR23X based Skyrad loggers were installed.  The result of 
no delay in these measurements results in an error in the measured resistance of the 
thermistors, Case1 and Dome2, and thus the calculated PIR1 and PIR2 irradiances.  The 
absolute value of the errors are inversely proportial to temperature.

At Pt Reyes, we are unable to determine if the excitation delay problem was present.  The 
first Skyrad datalogger program installed at PYE was correct but later versions modified 
and uploaded in March and April of 2005 may have had the Delay0 problem.

The problem also can not be determined from the data.  Pt. Reyes temperature fluctuations 
throughout the year are maritime and fall into a relatively narrow range in 2005 between 
2.5-20C.  The Delay0 problem introduces larger errors into PIR1 and PIR2 irradiance 
calculations as the temperature drops.  At the lowest temperature at Pt Reyes in 2005 (approx 
2.5C occurring in March) the largest PIR1 error would be -.48 W/m2 and PIR2 +.38 W/m2.  
The scale of these errors are smaller than the resolution of the instrument and are lost 
in the normal variation of the instrument readings. Cursory review of the thermistor data 
during cold periods does not show any discernable biases.  Furthermore, the data logger 
programming "error" due to the Delay0 problem is an order of magnitude less than the total 
estimated measurement uncertainty of the pyrgeometer data from any ARM installation (+/- 
5 W/sq m for 4-coeff and +/- 10 W/sq m for 2-coeff calibrations).

Due to these issues, no Delay0 corrections will be applied to PYE Skyrad data.
Suggestions: 
Measurements:pyeskyrad60sM1.b1:
  • down_long_hemisp_shaded2
  • down_long_hemisp_shaded1_std
  • down_long_hemisp_shaded1
  • down_long_hemisp_shaded2_max
  • down_long_hemisp_shaded2_std
  • down_long_hemisp_shaded1_max
  • inst_down_long_hemisp_shaded1_tp
  • inst_down_long_shaded2_case_temp
  • inst_down_long_shaded1_case_temp
  • inst_down_long_shaded2_dome_temp
  • down_long_hemisp_shaded1_min
  • down_long_hemisp_shaded2_min
  • inst_down_long_hemisp_shaded2_tp
  • inst_down_long_shaded1_dome_temp
more
pyeskyrad20sM1.a0:
  • inst_down_long_shaded2_dome_resist
  • inst_down_long_shaded2_case_resist
  • inst_down_long_shaded1_case_resist
  • inst_down_long_shaded1_dome_resist
  • inst_down_long_hemisp_shaded2_tp
  • inst_down_long_hemisp_shaded1_tp
more

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