Comparison of data for ozone amounts and ultraviolet doses obtained from simultaneous measurements with various standard ultraviolet instruments

Recent technological advances have made measurements of UV doses and ozone column amounts with multichannel filter instruments not only possible, but also an attractive alternative to other more labor-intensive and weather-dependent methods. Filter instruments can operate unattended for long periods of time, and it is possible to obtain accurate ozone column amounts even on cloudy days. We present results from extensive comparisons of the performance of several Norwegian Institute for Air Research UV (NILU-UV) and ground-based (GUV) filter instruments against Dobson and Brewer instruments and the earth probe-total ozone mapping spectrometer (EP-TOMS) instrument. The data used in the comparisons are from four different sites where we have had the opportunity to operate more than one type of UV instrument for extended periods of time. The sites include the University of Oslo, Norway; Ny-Alesund, Spitzbergen, Norway; the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center facilities at Wallops Island, Virginia, and Greenbelt, Maryland; and the University of Alaska Fairbanks. Our results show that ozone column amounts obtained with current filter-type instruments have an accuracy similar to those obtained with the Dobson instrument. The mean difference between NILU-UV and Dobson direct sun measurements were 0.4±1.9% (1σ) in Oslo for the period 2000 to 2003. The difference between a GUV and the same Dobson was 1.7±1.4% for the same time period. The mean difference between GUV and TOMS in Ny-Alesund 79 deg N and Oslo 60 deg N in the period 1996 to 1999 was <0.5±3% for days with noon solar zenith angles (SZAs)<80 deg.