Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
08/11/2006 | 1930 | 08/25/2006 | 1859 | Incorrect |
Subject: | NSA/GNDRAD/C1 - Incorrect calibration coefficients |
DataStreams: | nsagndradC1.00, nsagndrad20sC1.a1, nsagndrad60sC1.b1, nsagndrad20sC1.a0 |
Description: | BarrowC1, Gndrad. On Aug 11th the PSP-US was changed out and the Campbell program was changed to reflect this. However, an old program that uses the 4 coefficient PIR cal factors was used. The PIR-UIR was not changed out, however, the logger program coeffs reverted back to the 4 Coeffcients. The Eppley PIR-UIR coefficients for this S/N 30168F3 are : K0=0.0, K1(aka k)=.25253, K2= 1.0, K3=-4, Kr=0.0. |
Suggestions: | Either disregard the Gndrad PIR data for this time period or recalculate up_long_hemispheric irradiance based on the following information: 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 data found in the a1 or b1 datastream follow this procedure: 1) Obtain the following variables from the b1 datafile: inst_up_long_dome_temp inst_up_long_case_temp up_long_netir 2) For each one minute data entry in b1 backout the original PIR thermopile reading in uV using the incorrectly applied K1 coefficient. tpUIR[uV] = up_long_netir[uV]/0.2582[W/m2/uV] 3) Apply for each one minute data entry: WinUIR(W/m2)=k*V+ Sigma*Tc^4 -4*Sigma*(Td^4 - Tc^4) =[0.25253*tpUIR]+[Sigma*inst_up_long_case_temp^4] -[4*Sigma*(inst_up_long_dome_temp^4-inst_up_long_case^4)] where, Sigma = 5.6697E-8 (Stefan-Boltzman Const) Other datastream corrections (e.g. to a0) that use the UIR measurements will require similar corrections. For additional information see: http://www.arm.gov/publications/tech_reports/arm-05-111.pdf Either disregard the Gndrad PIR data for this time period or recalculate up_long_hem ispheric irradiance based on the following information: 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 data found in the a1 or b1 datastream follow this procedure: 1) Obtain the following variables from the b1 datafile: inst_up_long_dome_temp inst_up_long_case_temp up_long_netir 2) For each one minute data entry in b1 backout the original PIR thermopile reading in uV using the incorrectly applied K1 coefficient. tpUIR[uV] = up_long_netir[uV]/0.2582[W/m2/uV] 3) Apply for each one minute data entry: WinUIR(W/m2)=k*V+ Sigma*Tc^4 -4*Sigma*(Td^4 - Tc^4) =[0.25253*tpUIR]+[Sigma*inst_up_long_case_temp^4] -[4*Sigma*(inst_up_long_dome_temp^4-inst_up_long_case^4)] where, Sigma = 5.6697E-8 (Stefan-Boltzman Const) Other datastream corrections (e.g. to a0) that use the UIR measurements will require similar corrections. For additional information see: http://www.arm.gov/publications/tech_reports/arm-05-111.pdf Either disregard the Gndrad PIR data for this time period or recalculate up_long_hemi spheric irradiance based on the following information: 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 data found in the a1 or b1 datastream follow this procedure: 1) Obtain the following variables from the b1 datafile: inst_up_long_dome_temp inst_up_long_case_temp up_long_netir 2) For each one minute data entry in b1 backout the original PIR thermopile reading in uV using the incorrectly applied K1 coefficient. tpUIR[uV] = up_long_netir[uV]/0.2582[W/m2/uV] 3) Apply for each one minute data entry: WinUIR(W/m2)=k*V+ Sigma*Tc^4 -4*Sigma*(Td^4 - Tc^4) =[0.25253*tpUIR]+[Sigma*inst_up_long_case_temp^4] -[4*Sigma*(inst_up_long_dome_temp^4-inst_up_long_case^4)] where, Sigma = 5.6697E-8 (Stefan-Boltzman Const) Other datastream corrections (e.g. to a0) that use the UIR measurements will require similar corrections. For additional information see: http://www.arm.gov/publications/tech_reports/arm-05-111.pdf |
Measurements: | nsagndrad60sC1.b1: more
nsagndradC1.00: more nsagndrad20sC1.a1: more nsagndrad20sC1.a0: more |