Limited quality-control processing was applied to the data base as described below. The results are in the ".QC" files on the data-base tape by site, year, and month. For example:
FLA8705.QC is FSEC, 1987, May PGE8801.QC is PG&E, 1988, January SER8711.QC is SERI, 1987, November.These files correspond to the ".DAT" files for the same site, year, and month. Each data segment that includes a spectrum was processed through this quality-control procedure. If the atmospheric conditions were unstable, and a spectrum was not acquired, the broadband and meteorological data were included on the data-base tape, but no quality-control processing was applied.
An example of a segment of a ".QC" file is shown in Figure 6-3. The first line begins with a "Q" followed by the site, year, day, and time stamp. The last columns give the number of lines in the segment so the user can skip to the next segment. Following the first line are messages that were printed whenever the quality-control processing flagged a suspect or poor value.
Following the messages in an 80-character QC line listing the variables that were examined are one of three quality-control codes: 1, good; 2, marginal or suspect; and 3, missing or poor. The QC line was prepared using an automatic (computerized) check of the variables, and manual editing to include information from correspondence, log sheets, and visual inspection. Additional messages were added above the QC line if appropriate.
The two-character descriptors in the QC line are:
DN Direct-normal (thermopile) solar radiation, before the spectral scan DN Direct-normal (thermopile) solar radiation, after the spectral scan SN Direct-normal (silicon), before SN Direct-normal (silicon), after GN Global-normal, before GN Global-normal, after GH Global-horizontal (thermopile), before GH Global-horizontal (thermopile), after SH Global-horizontal (silicon), before SH Global-horizontal (silicon), after GT Global-tilt, before GT Global-tilt, after AL Albedo (W/m2) AP Albedo (%) PR Surface Pressure TC Temperature (°C) RH Relative Humidity WV Water Vapor (calculated from relative humidity) WS Wind Speed KT Kt KN Kn DG D/GH SP First Spectrum IT Integral of the First Spectrum SP Second Spectrum IT Integral of the Second SpectrumThe automatic tests that were performed to determine the QC code following each variable were:
(a) Check for missing or negative values for the broadband, solar radiation, meteorological, or atmospheric data, or the spectral integrals: <0 = Code 2 Missing (-9 or -99) = Code 3 (b) Check for atmospheric or broadband instrument instability using the difference and ratio of the before- and after-scan values and redundant measurements, if neither values are negative or missing: DN before/DN after if the absolute difference SN before/SN after is >10 W/m2 (e.g., DN before/SN before 5% of 200 W/m2) DN before/SN after and GH before/GH after SH before/SH after the ratio is <0.95 or >1.05, each of the GH before/SH before two variables = Code 2 GH after/SH after or GN before/GN after the ratio is <0.90 or >1.10, each of the GT before/GT after two variables = Code 3 (c) Check for DN > GN, or GH > ETR (extraterrestrial solar radiation) using ratios of the variables: DN before/GN before >0.95, each variable = Code 2 DN after/GN after >1.0, each variable = Code 3 GN before/ETR GN after/ETR (d) Check for values of Kt, Kn, and D/GH that are too high: KT (involves GH before and after and KT) KN (involves DN before and after and KN) DG (involves DN and GH, before and after, and DG) >0.95, each variable = Code 2 >1.0, each variable = Code 3 (e) Check the spectral integrals for unusual ratios to the corresponding broadband solar radiation value. IT/(Broadband value before and after) For direct spectra: <0.6 or >0.85, IT = Code 2 For global spectra: <0.7 or >0.95, IT = Code 2 For direct and global spectra: <0.5 or >1.0, IT = Code 3
We suggest that users of the data base develop a computer program to access fields in the QC line and to print the messages. This limited quality control will not flag all possible errors and additional tests should be applied depending on the users' requirements and applications.