PYE/SKYRAD/M1 - Reprocessed: Installation problems

The installation of the SKYRAD instrument was not without problems.  During all or part of 
the time period specified the calibrations were incorrect or incomplete, the downwelling 
diffuse and direct normal leads were switched, and the shadowband was severely out of 
alignment.

These data have been reprocessed to apply corrections as follows:

1) NIP & PSP-diffuse leads swapped 20050214-20050412.1645
     - swapped the NIP and PSP columns in the raw data files
     - backed out the original, incorrect calibrations 
     - applied correct calibrations
2) PSP-diffuse calibration error 050214-050215
     - backed out the original, incorrect calibration
     - applied correct calibrations
3) PSP-DS cal error 050214-050215
     - backed out the original, incorrect calibration
     - applied correct calibration
4) NIP cal error 050214-050215 and 050218-050401
     - backed out the original, incorrect calibrations
     - applied correct calibration

The reprocessed data were archived in February, 2007.

Users are encouraged to still use these data with caution only after a thorough quality 
review to be certain the data meet their requirements.

• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer2(down_long_hemisp_shaded2)
• inst_down_long_shaded1_case_temp
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer1(down_long_hemisp_shaded1)
• down_long_hemisp_shaded2_min
• inst_down_long_shaded2_dome_temp
• IR Brightness Temperature(sky_ir_temp)
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• sky_ir_temp_max
• short_direct_normal_std
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)
• down_long_hemisp_shaded1_min
• down_long_hemisp_shaded1_std
• sky_ir_temp_std
• sky_ir_temp_min
• inst_down_long_shaded2_case_temp
• down_long_hemisp_shaded2_max
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• down_short_diffuse_hemisp_std
• down_long_hemisp_shaded2_std
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• inst_down_long_shaded1_dome_temp
• down_short_hemisp_std
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• down_long_hemisp_shaded1_max
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)

• inst_down_long_shaded1_dome_resist
• inst_diffuse
• inst_sky_ir_signal
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)
• inst_direct_normal
• inst_down_long_shaded2_dome_resist
• inst_down_long_shaded1_case_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• inst_global
• inst_down_long_shaded2_case_resist

PYE/SKYRAD/M1 - Reprocessed: IRT configuration and calibration

The configuration of the IRT was inadvertently set to default and the program of the data 
loggers were changed to that used at TWP.C3.  This caused the calibration of the data to 
be wrong. It was corrected by reconfiguring the IRT and changing the conversion factors 
in the data logger program.

These data have been reprocessed to apply correct calibrations and the reprocessed data 
were archived in February, 2007.

• sky_ir_temp_std
• sky_ir_temp_min
• sky_ir_temp_max
• IR Brightness Temperature(sky_ir_temp)

• Raw data stream - documentation not supported

• inst_sky_ir_signal

PYE/SKYRAD/M1 - IRT bias

The SKYRAD IRT measured lower sky temperatures than the AERI.  This may have been due to a 
dirty mirror or lens.

• sky_ir_temp_std
• sky_ir_temp_min
• sky_ir_temp_max
• IR Brightness Temperature(sky_ir_temp)

PYE/SKYRAD/M1 - Reprocess: Longwave Calibration error

Modified pyrgeometer calibration procedures were implemented beginning in December 2003.  
These modified procedures introduced a calibration bias in the longwave data.  The 
previous procedures were re-implemented at all sites between December 2005 and February 2006 to 
restore proper calibrations.                                                             
                The data collected while the incorrect procedures were in place are 
being reprocessing to remove the calibration bias.  Note, this also affected standard 
deviation, maximum and minimum data fields.

• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer2(down_long_hemisp_shaded2)
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer1(down_long_hemisp_shaded1)

PYE/SKYRAD/M1 - Datalogger program error affected downwelling longwave

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.

• inst_down_long_shaded2_case_temp
• down_long_hemisp_shaded2_max
• down_long_hemisp_shaded2_std
• inst_down_long_shaded1_dome_temp
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer2(down_long_hemisp_shaded2)
• inst_down_long_shaded1_case_temp
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer1(down_long_hemisp_shaded1)
• down_long_hemisp_shaded2_min
• inst_down_long_shaded2_dome_temp
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• down_long_hemisp_shaded1_max
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)
• down_long_hemisp_shaded1_min
• down_long_hemisp_shaded1_std

• inst_down_long_shaded2_dome_resist
• inst_down_long_shaded1_case_resist
• inst_down_long_shaded1_dome_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)
• inst_down_long_shaded2_case_resist