The 2003 NOAA/NIST North American UV Radiometer Intercomparison was held from June 13th to 21st at Table Mountain, located 8 km north of Boulder, Colorado. The campaign is conducted every three years and is organized by the Central UV Calibration Facility (CUCF) of NOAA's Air Resources Laboratory. The primary purpose of the intercomparison is to assess the basic level of agreement of ultraviolet measuring instruments that are representative of the UV monitoring networks in North America and internationally. The participating agencies included the following:
Several different types of UV measuring instruments participated in the intercomparison. Instruments included several scanning spectroradiometers such as the USDA's U111 spectroradiometer, one of the EPA's Mark IV Brewer spectroradiometers, a BSI SUV-150 double-grating spectroradiometer from the NSF, and a Bentham spectroradiometer from IMUK. There were two rotating shadowband spectrograph instruments, one from the ASRC-SUNY and one from the USDA-NREL. Several moderate bandwidth radiometers were also present, including two of the USDA-NREL's UV Multi-Filter Rotating Shadowband Radiometers, two SR18s and one SR19 multi-filter instrument from SERC, and a GUV-511 radiometer from NSF-BSI. In addition, there were several UVB broadband radiometers from NOAA-ARL's SURFRAD Networks including three SL501s, three YESs, an EKO, and a Scintek UV broadband radiometer.
The intercomparison consisted of synchronized solar scans and instrument characterizations. The instruments were characterized for wavelength accuracy, slit-scattering function, and spectral irradiance responsivity. The responsivities were determined first by the participants and then using the CUCF's calibration equipment. The first part of the intercomparison consisted of a blind comparison of the data using calibration files determined by the participants. After a few days of intermittent sunshine during the set-up period, the weather became overcast with periods of rain throughout the week during the synchronized solar measurements. The participants agreed to stay an extra couple of days, which paid off with clear blue skies for most of Saturday. Initial results look promising for a solid data set of synchronized solar scans.