New Radiation Data Quality (QCRAD) VAP Release Now Available

Published: 24 June 2019
Southern Great Plains radiometers
A broadband radiometer station at ARM’s Southern Great Plains Central Facility near Lamont, Oklahoma, measures broadband solar (shortwave) and infrared (longwave) radiation. Data from this station have been processed as part of a new release for the Data Quality Assessment for ARM Radiation Data (QCRAD) value-added product.

A new level 2 (c2/s2) release for the Data Quality Assessment for ARM Radiation Data (QCRAD) value-added product (VAP) is now available. This release covers the following Atmospheric Radiation Measurement (ARM) user facility observatories and time periods:

  • Southern Great Plains Central Facility (SGP C1) near Lamont, Oklahoma, from June 29, 2017, to May 18, 2018
    • VAP data also available for SGP C1 broadband radiometer station (BRS) input from June 25, 2017, to May 18, 2018
  • SGP extended facility 13 (SGP E13) near Lamont from June 17, 2017, to May 18, 2018
  • North Slope of Alaska central facility (NSA C1) at Barrow, officially known as Utqiaġvik, from September 17, 2017, to September 29, 2018
  • extended mobile facility deployment at Oliktok Point, Alaska (OLI M1), from October 3, 2017, to September 27, 2018.

QCRAD has long been ARM’s recommended datastream for broadband surface irradiance measurements. The QCRAD methodology uses climatological analyses of the surface radiation measurements to define reasonable limits for testing the data for unusual values. QCRAD applies multiple data quality checks, corrects for errors due to infrared loss in shortwave (SW) radiometric measurements, and calculates a best-estimate total downwelling SW irradiance value.

The QCRAD VAP produces two daily files containing 1-minute radiation measurement fields and their quality control (QC) values. The *.c1 file—the asterisk represents the datastream name—includes auxiliary information and detailed qc flags. The *.s1 summary file includes a simplified version of the qc flags and fewer auxiliary data values.

During operational processing, the QCRAD VAP applies a generic correction to the downwelling SW hemispheric flux to correct for infrared loss within the radiometer. This operational processing produces the .c1 and .s1, or level 1, datastreams.

On a yearly basis, a more detailed correction that uses infrared loss corrections derived for the specific instruments—rather than the generic correction—is applied. This yearly processing produces the .c2 and .s2, or level 2, datastreams. This correction will affect the output of the downwelling SW values when the sum of the direct plus diffuse SW is not available as the best estimate for downwelling SW. When *.c2 and *.s2 files are available, they should be used.

Scientists can use the new QCRAD data now. Yearly processing for remaining ARM fixed sites will follow. To share your experience—such as how you use the data and how well it works for you—or to ask a question, contact Josh Howie.

More information on QCRAD is available on the VAP web page. To access these data, go to the ARM Data Center. (Go here to request an account.)

To cite the QCRAD data, please use doi:10.5439/1027372.