New Radiation Data Quality VAP Release for Eastern North Atlantic

Published: 20 July 2020
Radiometers at ARM's Eastern North Atlantic atmospheric observatory
Seen at ARM’s Eastern North Atlantic atmospheric observatory, sky radiometers on stand for downwelling radiation are among the instruments that contribute to the Data Quality Assessment for ARM Radiation Data (QCRAD) value-added product.

A new level 2 (c2/s2) release of the Data Quality Assessment for ARM Radiation Data (QCRAD) value-added product (VAP) is now available for the Atmospheric Radiation Measurement (ARM) user facility’s Eastern North Atlantic atmospheric observatory.

This release contains data from September 22, 2017, through October 17, 2019. The time frame includes the winter 2018 (January to February) intensive operational period of the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign.

QCRAD has long been the recommended ARM datastream for broadband surface irradiance measurements. QCRAD applies 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 routinely produces two daily files containing 1-minute radiation measurement fields and their 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 SW downwelling hemispheric flux to correct for infrared loss within the radiometer. This operational processing produces .c1 and .s1, or level 1, datastreams.

On a yearly basis, the VAP applies a more detailed correction that uses infrared loss corrections derived for the specific local climate and instruments, rather than the generic correction. The yearly processing produces .c2 and .s2, or level 2, datastreams. This correction will affect the output of the downwelling SW values for occasions 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 they work for you—or to ask a question, contact Josh Howie.

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

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

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ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.