Traceable Pyrgeometer Calibrations

Poster PDF

Description

The Atmospheric Radiation Measurement (ARM) program provides high quality radiometric data from approximately 150 instruments deployed at Southern Great Plains (SGP), Eastern North Atlantic (ENA), North Slope of Alaska (NSA), Oliktok (OLI), and the ARM Mobile Facilities (AMF) sites. These instruments are deployed on the Solar Infrared Radiation Station (SIRS), SKYRAD, and GNDRAD instrument platforms. In addition to the operational radiometers, there are more than 200 other radiometers that are calibrated and used for instrument swaps and replacements. The National Renewable Energy Laboratory (NREL) and ARM, through the Radiometric Calibration Facility (RCF) at the Southern Great Plains (SGP) site, provides Broadband Outdoor Radiometer Calibrations (BORCAL) for all shortwave (SW) and longwave (LW) radiometers that are deployed by the ARM program. The BORCAL-SW is traceable to the International System of Units (SI), through the World Radiometric Reference (WRR). On the other hand, the SI standard is not yet established for longwave measurements. Both NREL and ARM continue to improve radiometric measurement through the introduction of new methods to reduce uncertainty in calibration and field measurements. A significant part of this effort is to establish the longwave traceability to SI units and deploy the BORCAL-LW using an interim World Infrared Standard Group (WISG) for traceability. Deployment of BORCAL-LW capability has been performed under ARM program ECO-00781, “Establish Pyrgeometer Calibrations Traceable to the WISG”. The stated purpose of the ECO is to adopt the consensus WISG for calibrating pyrgeometers used by ARM for broadband longwave irradiance data collected from SIRS, SKYRAD, and GNDRAD instrument platforms. This poster presents the development, implementation, and operation of the LW-BORCAL system at the SGP RCF for the calibration of pyrgeometers that provide traceability to WISG.