The 1995 North American Interagency Intercomparison of Ultraviolet Monitoring Spectroradiometers

Area of Science:

• Atmospheric science
• Environmental monitoring
• Spectroradiometry

Background:

• Stratospheric ozone depletion concerns necessitate accurate monitoring of solar ultraviolet (UV) irradiance.
• North American government agencies established spectroradiometer networks for surface UV monitoring.
• Intercomparison studies are crucial for validating instrument accuracy and network comparability.

Purpose of the Study:

• To assess the accuracy of spectroradiometers in measuring solar UV irradiance.
• To compare measurement results from different UV monitoring networks.
• To evaluate instrument performance under field conditions.

Main Methods:

• The second North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was conducted in June 1995.
• Instruments were characterized for wavelength uncertainty, bandwidth, stray-light rejection, and spectral irradiance responsivity.
• Spectral irradiance responsivity was determined indoors and outdoors using a NIST standard lamp and field calibration unit.

Main Results:

• Spectral irradiance responsivity showed stability when instruments remained outdoors.
• Synchronized solar irradiance scans were performed over several days.
• Measured solar irradiances generally agreed within 3% when using NIST standard lamp responsivity and appropriate convolution functions.

Conclusions:

• The intercomparison validated the accuracy of spectroradiometers used in North American monitoring networks.
• Results demonstrate good agreement between instruments, supporting reliable UV irradiance data collection.
• The study confirms the capability of spectroradiometers for effective stratospheric ozone depletion monitoring.