Slant column measurements of O3 and NO2 during the NDSC intercomparison of zenith-sky UV-visible spectrometers in June 1996
Van Roozendael, M.
Kastad, Hoiskar, B.A.
Karlsen, Tornkvist, K.
Earth and related Environmental sciences
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In June 1996, 16 UV-visible sensors from 11 institutes measured spectra of the zenith sky for more than 10 days. Spectra were analysed in real-time to determine slant column amounts of O3 and NO2. Spectra of Hg lamps and lasers were measured, and the amount of NO2 in a cell was determined by each spectrometer. Some spectra were re-analysed after obvious errors were found. Slant columns were compared in two ways: by examining regression analyses against comparison instruments over the whole range of solar zenith angles; and by taking fractional differences from a comparison instrument at solar zenith angles between 85°and 91°. Regression identified which pairs of instruments were most consistent, and so which could be used as universal comparison instruments. For O3, regression slopes for the whole campaign agreed within 5% for most instruments despite the use of different cross-sections and wavelength intervals, whereas similar agreement was only achieved for NO2 when the same cross-sections and wavelength intervals were used and only one half-day's data was analysed. Mean fractional differences in NO2 from a comparison instrument fall within ± 7% (1-sigma) for most instruments, with standard deviations of the mean differences averaging 4.5%. Mean differences in O3 fall within ± 2.5% (1-sigma) for most instruments, with standard deviations of the mean differences averaging 2%. Measurements of NO2 in the cell had similar agreement to measurements of NO2 in the atmosphere, but for some instruments measurements with cell and atmosphere relative to a comparison instrument disagreed by more than the error bars.
CitationRoscoe, H.K.; Johnston, P.V.; Van Roozendael, M.; Richter, A.; Sarkissian, A.; Roscoe, J.; Preston, K.E.; Lambert, J.-C.; Hermans, C.; Decuyper, W.; Dzienus, S.; Winterrath, T.; Burrows, J.; Goutail, F.; Pommereau, J.-P.; D'Almeida, E.; Hottier, J.; Coureul, C.; Didier, R.; Pundt, I.; Bartlett, L.M.; McElroy, C.T.; Kerr, J.E.; Elokhov, A.; Giovanelli, G.; Ravegnani, F.; Premuda, M.; Kostadinov, I.; Erle, F.; Wagner, T.; Pfeilsticker, K.; Kenntner, M.; Marquard, L.C.; Gil, M.; Puentedura, O.; Yela, M.; Arlander, D.W.; Kastad, Hoiskar, B.A.; Tellefsen, C.W.; Karlsen, Tornkvist, K.; Heese, B.; Jones, R.L.; Aliwell, S.R.; Freshwater, R.A. (1999). Slant column measurements of O3 and NO2 during the NDSC intercomparison of zenith-sky UV-visible spectrometers in June 1996. , Journal of Atmospheric Chemistry, Vol. 32, Issue 2, 281-314, DOI: 10.1023/A:1006111216966.