SGP/SIRS/E11 - Reprocess: Incorrect shortwave radiometer calibration coefficients

During the pyrgeometer instrument (PIR) changeout a datalogger program was loaded with 
incorrect calibration coefficients for the shortwave instruments.  The affected measurements 
(instruments) were: downwelling diffuse (8-48), upwelling shortwave (PSP), direct normal 
(NIP) and downwelling shortwave (PSP)

Field tech reports the datalogger program was corrected on 4/27/04.  Archive data review 
shows this was not the case and the corrected datalogger program was uploaded sometime 
late day 5/4/04. The end date for this DQR was chosen to be 5/5/04 0000 the first full day 
of the correct datalogger program.

Recalculate irradiances by determining original mV signal and reapplying the correct 
calibration coefficients.  For each one minute irradiance value perform the following 
calculations by instrument:
DD(corrected) = (DD/107.24)*123.27
US(corrected) = (US/113.19)*127.75
NIP(corrected)= (NIP/120.17)*126.69
DS(corrected) = (DS/118.46)*126.56

• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Upwelling (10 meter) Shortwave Hemispheric Irradiance, Ventilated Pyranometer,
  Standard Deviation(up_short_hemisp_std)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Minima(down_short_diffuse_hemisp_min)
• Upwelling (10 meter) Shortwave Hemispheric Irradiance, Ventilated Pyranometer(up_short_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Standard Deviation(short_direct_normal_std)
• Shortwave Direct Normal Irradiance, Pyrheliometer(short_direct_normal)
• Upwelling (10 meter) Shortwave Hemispheric Irradiance, Ventilated Pyranometer,
  Minima(up_short_hemisp_min)
• Upwelling (10 meter) Shortwave Hemispheric Irradiance, Ventilated Pyranometer,
  Maxima(up_short_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Standard Deviation(down_short_diffuse_hemisp_std)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)

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

SGP/SIRS/E11 - Reprocess: Incorrect calibration coefficients applied to upwelling longwave

While correcting calibration coefficients (see D040831.5) a new datalogger program was 
loaded which applied the wrong serial number and calibration coefficients to the upwelling 
longwave measurements.

For a PIR mounted in an upwelling measurement orientation (UIR), the
thermopile output is extremely low compared to a downwelling PIR (DIR).
In addition, the UIR case and dome temperature differences are much
smaller than a DIR.  This results in the pyrgeometer receiver radiation 
term, Wr (NREL/Hickey equation) or Wc (Albrecht/Cox equation), dominating
all other terms of the infrared radiant flux equation.

Since the receiver radiation term uses coefficients in both forms of
the pyrgeometer equations nearly equal to 1.0 +- <1% the result is a
measurement of incoming longwave radiant flux relatively insensitive 
to the installed instrument - so long as it is an Eppley PIR.
		
Evaluation of the problem data shows the expected error of the data
(before correction) will be within 1% - less than the uncertainty of 
the instrument (Eppley PIR greater of 5% or 5 W/m2)
		
To correct the one minute UIR data found in the raw or b1 datastream follow
this procedure:
1) Obtain the following variables from the b1 datafile for each minute:
     Td = inst_up_long_dome_temp[degK]
     Tc = inst_up_long_case_temp[degK]
     Wnet = up_long_netir[W/m2]

2) For each one minute data entry in b1 backout the thermopile voltage
     V[uV] = Wnet/K1(wrongly applied UIR cal coeffs) = 
up_long_netir[W/m2]/0.24832[W/m2/uV]

3) Apply for each one minute data entry:
     Winc [W/m^2] = K0+K1*V+ K2*Sigma*Tr^4 + K3*Sigma*(Td^4 - Tr^4)
   where,
     Winc= incoming radiation [W/m2]
     V   = PIR thermopile voltage [uV]
     K0 =  offset W/m2 = -6.93
     K1 =  1/Responsivity of TP [W/m2*uV] = .24764
     K2 =  case emittance w/ thermistor correction [unitless] = 1.010
     K3 =  thermal conductance between dome and receiver & therm. correction [unitless] = 
-3.886
     Sigma= 5.67 x 10^-8 [W/(sq mK^4)] = Stephan-Boltzman Constant
     Td  = PIR dome thermistor temperature [deg K]
     Tr = Tc + 0.0007044 * V
         where 7.044e-4 is empirically derived for an Eppley PIR
     Tc  = PIR case receiver temperature [deg K]

Other datastream corrections that use the UIR measurements will require
similar corrections.

See the following web site for additional information on the pyrgeometer
equations, specifically sections 2.1(Single Calibration Factor Approach)
and 2.2 (Four Coefficient Calibration Approach)
     http://www.arm.gov/docs/instruments/static/pyrg.html

• Upwelling Longwave Hemispheric Net Infrared(up_long_netir)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Maxima(up_long_hemisp_max)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Minima(up_long_hemisp_min)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer(up_long_hemisp)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Standard Deviation(up_long_hemisp_std)

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

SGP/SIRS/E11 - 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 Longwave Hemispheric Net Infrared(up_long_netir)
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer(up_long_hemisp)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer(down_long_hemisp_shaded)