Calibration of solar radiometers with traceability to the world radiometric reference using an absolute cavity radiometer

Abstract

This study presents the actual field results from a calibration procedure of reference solar radiometers using an Absolute Cavity Radiometers (ACR), which is directly traceable to the World Radiometric Reference (WRR) scale maintained by the World Radiation Center (WRC). The pyranometer and pyrheliometer traceability is established using Eppley’s AHF-AWX ACR as per the prescribed standards. The Eppley solar radiometers were exposed to solar irradiance for 3.5 years and the Hukseflux solar radiometers were exposed to solar irradiance for 1.5 years. The deviation of the new sensitivity values from the old sensitivity values is reported to be 5.42% (pyranometer, Eppley PSP), −0.21% (pyranometer, Hukseflux SR25), 0.23% (pyrheliometer, Eppley NIP) and 0.4% (pyrheliometer, Hukseflux DR03). The uncertainty values are found to be ±0.04 µV/Wm−2, ±0.05 µV/Wm−2, ±0.03 µV/Wm−2 and ±0.03 µV/Wm−2 for Eppely PSP, Hukseflux SR25, Eppley NIP and Hukseflux DR03 solar radiometers, respectively.