| DQR ID | Subject | Data Streams Affected |
|---|---|---|
| D040226.2 | SGP/SIRS/E11 - PSP dome contamination | sgpsirsE11.00, sgpsirsE11.b1, sgpsirs20sE11.a0 |
| D040831.5 | SGP/SIRS/E11 - Reprocess: Incorrect shortwave radiometer calibration coefficients | sgpsirsE11.00, sgpsirsE11.b1 |
| D040903.1 | SGP/SIRS/E11 - Reprocess: Incorrect calibration coefficients applied to upwelling longwave | sgpsirsE11.00, sgpsirsE11.b1 |
| D060403.1 | SGP/SIRS/E11 - failed ventilator fan | sgpsirsE11.00, sgpsirsE11.b1, sgpsirs20sE11.a0 |
| Start Date | Start Time | End Date | End Time |
|---|---|---|---|
| 02/20/2004 | 1500 | 03/01/2004 | 1300 |
| Subject: | SGP/SIRS/E11 - PSP dome contamination |
| DataStreams: | sgpsirsE11.00, sgpsirsE11.b1, sgpsirs20sE11.a0 |
| Description: | Measured values of diffuse shortwave downwelling radiation fluctuated below derived values of downwelling shortwave radiation during the afternoon hours under clear conditions, probably due to a dirty PSP dome. SMOS precipitation and wind speed data reveal rain and wind on 02/19/03 at 2300 GMT probably contaminated the PSP dome with dirt. Precipitation of .4mm on 02/29/04 1400 seems to have effectively cleared the PSP dome since PSP data on 03/01/04 compares correctly to direct and diffuse components. |
| Measurements: | sgpsirsE11.b1:
sgpsirsE11.00:
sgpsirs20sE11.a0:
|
| Start Date | Start Time | End Date | End Time |
|---|---|---|---|
| 02/17/2004 | 1741 | 05/05/2004 | 0000 |
| Subject: | SGP/SIRS/E11 - Reprocess: Incorrect shortwave radiometer calibration coefficients |
| DataStreams: | sgpsirsE11.00, sgpsirsE11.b1 |
| Description: | 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 |
| Measurements: | sgpsirsE11.b1:
sgpsirsE11.00:
|
| Start Date | Start Time | End Date | End Time |
|---|---|---|---|
| 05/04/2004 | 0000 | 06/22/2004 | 1855 |
| Subject: | SGP/SIRS/E11 - Reprocess: Incorrect calibration coefficients applied to upwelling longwave |
| DataStreams: | sgpsirsE11.00, sgpsirsE11.b1 |
| Description: | 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 |
| Measurements: | sgpsirsE11.b1:
sgpsirsE11.00:
|
| Start Date | Start Time | End Date | End Time |
|---|---|---|---|
| 10/01/2005 | 0000 | 04/04/2006 | 1545 |
| Subject: | SGP/SIRS/E11 - failed ventilator fan |
| DataStreams: | sgpsirsE11.00, sgpsirsE11.b1, sgpsirs20sE11.a0 |
| Description: | E11 downwelling hemispheric shortwave instrument (Eppley PSP) has shown larger and larger nighttime offsets (from -5 to -10 W/m2) since October. A failed ventilator fan was discovered during PM and replaced on 4/4/2006. |
| Measurements: | sgpsirsE11.b1:
sgpsirsE11.00:
sgpsirs20sE11.a0:
|