DQR ID | Subject | Data Streams Affected |
---|---|---|
D010423.14 | SGP/SIRS/E13 - Diffuse Pyranometer Thermal Offsets | sgpsirsE13.a0, sgpsirsE13.a1 |
D010907.4 | "bsrn" platform at SGP data problem | sgpbsrnC1.00, sgpbsrnC1.a0, sgpbsrnC1.a1, sgpbsrn1duttC1.c1 |
D050420.2 | SGP/BSRN/C1 - Reprocess: Adjust Direct Normal Irradiance | sgpbsrnC1.00, sgpbsrnC1.a0, sgpbsrnC1.a1 |
D050502.8 | SGP/SIRS/E13 - SWFANAL Data description error | sgp1swfanalsirs1longE13.c1, sgp15swfanalsirs1longE13.c1 |
Start Date | Start Time | End Date | End Time |
---|---|---|---|
08/29/1997 | 0421 | 02/22/2001 | 2021 |
Subject: | SGP/SIRS/E13 - Diffuse Pyranometer Thermal Offsets |
DataStreams: | sgpsirsE13.a0, sgpsirsE13.a1 |
Description: | Broadband downwelling shortwave diffuse (sky) irradiance measurements available from SIRS during the period of this Data Quality Report (DQR), require adjustment for thermal offsets. These thermal, or ?zero? offsets refer to the generally reduced output signals from a shaded pyranometer due to the exchange of longwave (infrared) irradiance between the single black thermopile detector, the protective glass domes surrounding the detector, and the atmosphere. Originally considered an acceptable nighttime response of thermopile-type pyranometers, the generally negative bias is now recognized to significantly effect the accuracy of SIRS diffuse irradiance data during daylight periods. Studies of the Eppley Laboratory, Inc. Model PSP (Precision Spectral Pyranometer), used for the SIRS measurements of diffuse irradiance, suggest the thermal offset correction can range from near 0 to as much as 30 Watts per square meter, depending on the coincident net longwave, or infrared irradiance [1, 2]. Under very clear-sky conditions, the diffuse irradiance from a shaded PSP can be less than the minimum physical limit defined by radiative transfer model estimates based only on Rayleigh scattering effects. A correction method has been developed for adjusting SIRS diffuse irradiance data [3]. The resulting Value Added Product (VAP) will be applied to SIRS data for the period of this DQR. The VAP will not be applied to SIROS data collected before the instrument platform was converted to SIRS. Additionally, the Model PSP radiometer has been replaced by a Model 8-48 which uses a black and white thermopile detector known to reduce the thermal offset errors to less than 2 Watts per square meter [3]. The radiometer replacement at this SIRS location was completed on the ending date of this DQR. References: 1. Gulbrandsen, A., 1978: On the use of pyranometers in the study of spectral solar radiation and atmospheric aerosols. J. Appl. Meteorol., 17, 899-904. 2. Cess, R. D., X. Jing, T. Qian, and M. Sun, 1999: Validation strategies applied to the measurement of total, direct and diffuse shortwave radiation at the surface. J. Geophys. Res. 3. Dutton, E.G., J. Michalsky, T. Stoffel, B. Forgan, J. Hickey, D. Nelson, T. Alberta, and I. Reda, 2001: Measurement of Broadband Diffuse Solar Irradiance Using Current Commercial Instrumentation With a Correction for Thermal Offset Errors. J. Atmos. Oceanic Tech. Vol 18, No. 3, 297-314. (March 2001) |
Measurements: | sgpsirsE13.a0:
sgpsirsE13.a1:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
10/01/1998 | 0000 | 01/22/2001 | 2359 |
Subject: | "bsrn" platform at SGP data problem |
DataStreams: | sgpbsrnC1.00, sgpbsrnC1.a0, sgpbsrnC1.a1, sgpbsrn1duttC1.c1 |
Description: | As reported in ARM Technical Report ARM-TR-002, the 'bsrn' data at the SGP CF was not in agreement with the co-located SIRS E13 and C1 data. Subsequent discussion led to the conclusion that ther was a voltage problem with the 'bsrn' data logger. In development and testing of the Diffuse Correction and Best Estimate Flux VAPs, it has been shown that all 'bsrn' data, all instruments, suffered this data logger problem. The result is noisy and slightly offset values, seemingly at random throughout the period from October 1998 through the end of the 'bsrn' data stream and it's replacement by the BRS system. All this data needs to be colored 'questionable', and all data users need to be informed that either the SIRS E13 or SIRS C1 data should be used instead. |
Measurements: | sgpbsrnC1.00:
sgpbsrnC1.a1:
sgpbsrnC1.a0:
sgpbsrn1duttC1.c1:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
07/28/2000 | 1430 | 01/22/2001 | 1739 |
Subject: | SGP/BSRN/C1 - Reprocess: Adjust Direct Normal Irradiance |
DataStreams: | sgpbsrnC1.00, sgpbsrnC1.a0, sgpbsrnC1.a1 |
Description: | Direct normal broadband shortwave irradiance measured by NIP s/n 30721E6 was found to have a 4.1% negative bias when compared in-situ with absolute cavity radiometer measurements taken on August 21, 2000. The estimated measurement uncertainty of the calibration of NIP s/n 30721E6 on July 18, 2000 was -2.8% to +3.5%. The additional uncertainties of the field (rather than calibration) data acquisition system and installation contribute to the large negative bias found in the data on August 21, 2000. Data from NIP s/n 30721E6 can be adjusted according to the in-situ comparisons to reduce the apparent measurement bias. |
Measurements: | sgpbsrnC1.00:
sgpbsrnC1.a1:
sgpbsrnC1.a0:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
10/01/1995 | 0000 | 10/28/2003 | 2359 |
Subject: | SGP/SIRS/E13 - SWFANAL Data description error |
DataStreams: | sgp1swfanalsirs1longE13.c1, sgp15swfanalsirs1longE13.c1 |
Description: | The long name attribute for the cloud effect fields incorrectly defines the cloud effect to be the difference between the clearskyfit and measured values: "Difference: ***fluxdn_clearskyfit - ***fluxdn_measured (***fcg)" ; The cloud effects are correctly calculated by subtracting the irradiance calculated in the clear sky fit from the measured irradiance. "Difference: ***fluxdn_measured - ***fluxdn_clearskyfit (***fcg)" ; NOTE: this is just a documentation error. The data are correctly calculated. |
Measurements: | sgp15swfanalsirs1longE13.c1:
sgp1swfanalsirs1longE13.c1:
|