New Broadband Irradiance Data Produced for 2 ARM Sites

Published: 28 April 2023
Radiometers in overcast conditions at Oliktok Point, Alaska, with tundra stretching out across the horizon
This collection of radiometers at Oliktok Point, Alaska, provided continuous measurements of broadband shortwave (solar) and longwave (infrared) irradiances for downwelling components. ARM stopped collecting data at Oliktok Point in June 2021 after almost eight years.

New c2-level data are available from the Data Quality Assessment for ARM Radiation Data (QCRAD) product at Oliktok Point, Alaska, and the 2021–2022 TRacking Aerosol Convection interactions ExpeRiment (TRACER) near Houston, Texas. The new Oliktok Point data cover the period of August 7, 2020, to June 15, 2021.

QCRAD has long been the recommended ARM datastream for broadband surface irradiance measurements.

QCRAD processing involves two steps. During c1-level operational processing, QCRAD applies a generic correction to the shortwave downwelling hemispheric flux to correct for infrared loss within the unshaded pyranometer. The c1-level processing also applies multiple data quality checks and calculates a best-estimate total downwelling shortwave irradiance value.

The c2-level processing, performed yearly, replaces the generic correction with a more detailed correction that uses infrared loss corrections derived for the specific instruments. This correction will affect the output of the downwelling shortwave values for those occasions where the sum of the direct plus diffuse shortwave is not available as the “best estimate” for downwelling shortwave. When c2 files are available, they should be used.

Scientists can use the c2-level QCRAD data from Oliktok Point and TRACER now. Access these data in the ARM Data Center. (Go here to request an account to download the data.)

More information about QCRAD is available on the product web page. To share your experience using the data or to ask a question, contact ARM translator Damao Zhang.

To cite the QCRAD data, please use doi:10.5439/1227214.

Please note: The 2019–2020 c2-level data from Oliktok Point will be created and released after input data from the sky radiometers on stand for downwelling radiation are reprocessed for the period of August 26, 2019, to April 24, 2020. Currently, c1-level data are available from August 26, 2019, to August 6, 2020.

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