SGP/SIRS/E9 - Unknown -failed PSP ventilator fan

Downwelling shortwave hemispheric (DSH) readings appear to have a slight to moderate 
negative offset from derived DSH values.  At night, this negative offset causes qc flags 
(since values are below the minimum threshold of -10 W/m^2).  Differences between derived and 
actual DSH values are sometimes on the order of 50 W/m^2 due to this offset. 
The offset was discovered to be due to a failed ventilator fan which is used to clear the 
dome of the PSP, the instrument which measures the DSH.  The ventilator likely seized or 
was intermittent and heated the PSP base giving an erroneous DSH reading.  Field techs 
replaced the fan on 01/25/2005 1745GMT.  The DSH has been reading normally since that time.

• Instantaneous Downwelling Hemispheric Shortwave, Unshaded Pyranometer Thermopile
  Voltage(inst_global)

• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

SGP/SIRS/E9 - Downwelling Shortwave values low

Downwelling Shortwave Hemispheric (DSH) irradiance values from the pyranometer instrument 
were frequently below the MIN value of -10 W/m^2 at night.  DSH values also frequently 
disagreed with derived readings (at times well over 50 W/m^2 difference) during the 
daylight hours, especially in the morning. Field techs performed maintenance but could not find 
obvious instrument or connection problems.  

The low DSH values during nighttime were on the threshold of acceptable. Largest offsets 
acceptable with these pyranometers is typically -10 W/m2.  The large derived vs. actual 
DSH differences during the daylight hours are the subject of ongoing ARM investigation. No 
instrument problems could be identified.

• Instantaneous Downwelling Hemispheric Shortwave, Unshaded Pyranometer Thermopile
  Voltage(inst_global)

• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

SGP/SIRS/E9 - 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.

• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer(up_long_hemisp)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer(down_long_hemisp_shaded)
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Upwelling Longwave Hemispheric Net Infrared(up_long_netir)