UV-B Robertson-Berger meter characterization and field calibration

Area of Science:

• Atmospheric science
• Radiometry
• Solar radiation physics

Background:

• The New Zealand Meteorological Service has utilized Robertson-Berger meters (RB meters) for solar UV-B radiation monitoring over the last decade.
• Analysis of the instrument's radiometric properties confirms agreement with established Berger standards.
• Previous studies have not fully detailed the theoretical response of RB meters, particularly concerning cosine response.

Purpose of the Study:

• To present a comprehensive theoretical model of the Robertson-Berger meter's response, incorporating its cosine response.
• To validate this theoretical model using field measurements from both RB meters and a spectral radiometer.
• To derive an accurate calibration for the RB meter based on validated theoretical and experimental data.

Main Methods:

• Developed a detailed theoretical treatment of the Robertson-Berger meter's response, accounting for imperfect cosine response.
• Collected field data using both a Robertson-Berger meter and a double monochromator spectral radiometer under cloud-free conditions.
• Modeled the downward radiation field as direct solar and isotropic diffuse components to validate the theoretical model and derive calibration.

Main Results:

• The theoretical model for the RB meter's response, including cosine response, was validated through field measurements.
• A precise calibration was derived, establishing a conversion factor for the RB meter.
• A RB meter count was found to equate to 0.25 +/- 0.02 Jm(-2) for 300-nm radiation at vertical incidence.

Conclusions:

• The theoretical model accurately describes the Robertson-Berger meter's performance.
• The derived calibration provides a reliable method for quantifying solar UV-B radiation using RB meters.
• This research enhances the accuracy of UV-B radiation measurements for environmental and climate studies.