TWP/GNDRAD/C2 - IRT problem

The GNDRAD IRT exhibited a positive bias compared to the PIR from 2100 to 0700 UTC each 
day. The problem was corrected by removing the signal cable, cleaning the contacts, and 
reconnecting the cable.

• sfc_ir_temp_std
• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)

TWP/GNDRAD/C2 - incorrect IRT calibration

When the GNDRAD data logger was upgraded, the calibration offset for the IRT was initially 
incorrect.

• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)

TWP/GNDRAD/C2 - IRT connector

The IRT had a problem with the connector of either the signal or power cable which 
produced an output of 0 volts equivalent to a measurement of 223K. The problem was corrected 
when the connectors were cleaned and tightened.

• sfc_ir_temp_std
• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)

TWP/GNDRAD/C2 - IRT power supply failed

The IRT output dropped to its minimum output of 223 K (0 volts).  It was determined the 24 
V DC converter had failed.  The converter was replaced on 16 August and the instrument 
began reporting normally again.  The IRT data are unusable during the five day period when 
the DC converter was faulty.

The GNDRAD (down-looking) IRT is used primarily for surface temperature.  The PIR can be 
used for this purpose by inverting the IR flux equation, Flux = sigma*temperature^4 where 
sigma = 5.67x10-8 W/m^2K^4.  But, unlike the IRT, the PIR measurement is strongly 
effected by the air temperature in addition to the surface temperature.  At night, when the air 
temperature approaches the surface temperature, the PIR provides a good estimate of the 
surface temperature.  During the day, however, the PIR tends to underestimate the ground 
temperature,  particularly on sunny days.  The magnitude of the underestimate can be 
estimated by evaluating periods when both instruments are operating but is typically on the 
order of 5-10C.

• irt1_mean
• irt1_sd
• irt1_min
• irt1_max

• Raw data stream - documentation not supported

TWP/GNDRAD/C2 - Gndrad inverted for radiometer

Gndrad instruments PIR and PSP inverted for replacement instrument
installation and comparison

• psp1_min
• sfc_ir_temp_std
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• pir1_min
• pir1_max
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Minima(up_short_hemisp_min)
• psp1_mean
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)
• psp1_max
• up_short_hemisp_std
• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• psp1_sd
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Maxima(up_short_hemisp_max)
• Effective Surface (Skin) Temperature(sfc_ir_temp)
• up_long_hemisp_std
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• pir1_mean
• pir1_sd

TWP/GNDRAD/C2 - 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.

• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)

TWP/GNDRAD/C2 - IRT signal

When the other GNDRAD radiometers were replaced on 12/3/2006, the quality of the IRT 
signal began to degrade until 12/26 when it became unusable. The instrument was replaced on 
2/4/2007.

• sfc_ir_temp_std
• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)

TWP/GNDRAD/C2 - Reprocess: IRT calibration

The configuration of the IRT was set to that used at TWP/C3. This caused the calibration 
of the data to be wrong. It was corrected by reconfiguring the IRT to match the datalogger 
program.
   
These data can be reprocessed and corrected by adding 10K, i.e. sfc_ir_temp(new) = 
sfc_ir_temp(old) + 10K.

• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)

TWP/GNDRAD/C2 - Reprocessed: Incorrect calibration

The Gndrad PSP was changed out 11/25 but the datalogger program was not updated until 
11/30.

PSP #31293 installed 20071125.2202.  Correct calibration coefficient = 123.46.

Reprocessed to correct upwelling shortwave hemispheric irradiance (US) by:
US(new) = (US(old) / 123.56 ) * 123.46

Reprocessing completed March 2008.

• up_short_hemisp_std
• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Minima(up_short_hemisp_min)
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Maxima(up_short_hemisp_max)

• inst_up_short_hemisp