Real-time ultraviolet and column ozone from multichannel ultraviolet radiometers deployed in the National Science Foundation’s ultraviolet monitoring network

Multichannel moderate-bandwidth ground-based ultraviolet (GUV) filter radiometers have recently been installed at several sites of the U.S. National Science Foundation's UV monitoring network where they complement high-resolution solar UV-100 (SUV-100) spectroradiometers. The five GUV channels are characterized for their spectral response and calibrated against SUV systems as well as irradiance standard lamps. Results indicate that accurate spectral characterization of GUV channels in the UV-B is crucial for obtaining high-quality UV measurements, in particular if instruments are calibrated with standard lamps. Using an inversion algorithm suggested by Dahlback (1996), total column ozone and approximately 30 different UV integrals and dose rates are routinely calculated from GUV measurements. For UV-A irradiance, GUV and SUV data agree to within ±5% for solar zenith angles (SZAs) up to 90 deg. A similarly good agreement can be achieved for the UV index if solar measurements are restricted to SZAs smaller than 78 deg. The agreement for data products that are dominated by wavelengths in the UV-B is generally worse, but can be substantially improved if GUV instruments are equipped with an additional channel at 313 nm. GUV total column ozone values agree on average to within ±5% with observations from the National Aeronautics and Space Administration's (NASA's) total ozone mapping spectrometer (TOMS) on board the earth probe satellite. GUV data products are disseminated via the website www.biospherical.com/NSF in near real time.