Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

qcrad > Data Quality Assessment for ARM Radiation DataVAP Type(s) > Baseline

The QCRAD VAP has been developed to assess the data quality and enhance data continuity for the ARM radiation data collected at all ARM central and extended facilities. The QCRAD methodology uses climatological analyses of the surface radiation measurements to define reasonable limits for testing the data for unusual data values. The main assumption is that the majority of the measurements are “good” data, which for field sites operated with care, such as ARM’s, is a reasonable assumption. Data that fall outside the normal range of occurrences are labeled either “indeterminate” or “bad,” depending on how far outside the normal range the particular data reside. The methodology not only sets fairly standard maximum and minimum value limits, but includes many cross-comparisons based on what we have learned about how these instruments behave in the field in developing other VAPs such as the Diffuse IR Loss Correction VAP (Younkin and Long 2004) and the Best Estimate Flux VAP (Shi and Long 2002).

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The QCRAD VAP produces daily files containing 1-minute radiation measurement fields and their QC values. The *.c1-level file includes auxiliary information and detailed ancillary quality control (aqc) and bit-packed standard qc flags. The *.c1 files are produced with a delay of two days from the data being collected, and this is considered operational processing.

During operational processing, the QCRAD VAP applies a generic correction to the shortwave (SW) downwelling hemispheric flux to correct for infrared loss within the radiometer. On a yearly basis, a more detailed correction that uses fits derived for the specific instruments (rather than the generic correction) is applied. This correction will affect the output of the downwelling SW values for those occasions for which the sum of the direct plus diffuse SW is not available as the “best estimate” for downwelling SW. So that the user may easily tell whether this full correction has been applied, files that have had the full correction implemented are labeled as *.c2. Once the *.c2 files are available, they will replace the *.c1 files in the ARM Data Center.

Additional Information on the QCRAD VAP

ARM Technical Report: The QCRad Value-Added Product: Surface Radiation Measurement Quality Control Testing, Including Climatologically Configurable Limits. Atmospheric Radiation Measurement Technical Report, ARM TR-074, 69 pp. Long, CN, and Y. Shi. 2006. Available via

Shi, Y, and CN Long. 2005. Examples of Detecting Measurement Errors with the QCRad VAP. 15th ARM Science Team Meeting Proceedings, Daytona Beach, Florida, March 14-18, 2005. Available online at

Shi, Y, and CN Long. 2004. Techniques and Methods Used to Determine the Best Estimate of Total Downwelling Shortwave Radiation. 14th ARM Science Team Meeting Proceedings, Albuquerque, New Mexico, March 22-26, 2004. Available online at

Younkin, K, and CN Long. 2004. Improved Correction of IR Loss in Diffuse Shortwave Measurements: An ARM Value Added Product. Atmospheric Radiation Measurement Program Technical Report, ARM TR-009, Available online at

Shi, Y, and CN Long. 2003. Preliminary Analysis of Surface Radiation Measurement Data Quality at the SGP Extended Facilities. 13th ARM Science Team Meeting Proceedings, Broomfield, Colorado, March 31-April 4, 2003. Available online at

Shi, Y, and CN Long. 2002. Best Estimate Radiation Flux Value-Added Product: Algorithm Operational Details and Explanations, Atmospheric Radiation Measurement Program Technical Report. ARM TR-008, Available online at


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gndrad: Ground Radiometers on Stand for Upwelling Radiation

mfrsr: Multifilter Rotating Shadowband Radiometer

sirs: Solar and Infrared Radiation Station for Downwelling and Upwelling Radiation

skyrad: Sky Radiometers on Stand for Downwelling Radiation