Bohn, B., Corlett, G. K., Gillmann, M., Sanghavi, S., Stange, G., Tensing, E., Vrekoussis, M., Bloss, W. J., Clapp, L. J., Kortner, M., Dorn, H.-P., Monks, P. S., Platt, U., Plass-Dülmer, C., Mihalopoulos, N., Heard, D. E., Clemitshaw, K. C., Meixner, F. X., Prevot, A. S. H. and Schmitt, R. (2008) Photolysis frequency measurement techniques: results of a comparison within the ACCENT project. Atmospheric Chemistry and Physics, 8 (17).
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An intercomparison of different radiometric techniques measuring atmospheric photolysis frequencies j(NO2), j(HCHO) and j((OD)-D-1) was carried out in a two-week field campaign in June 2005 at Julich. Germany. Three double-monochromator based spectroradiometers (DM-SR), three single-monochromator based spectroradiometers with diode-array detectors (SM-SR) and seventeen filter radiometers (FR) (ten j(NO2))-FR, seven j((OD)-D-1)-FR) took part in this comparison. For j(NO2), all spectroradiometer results agreed within +/- 3%. For j(HCHO), agreement was slightly poorer between -8% and +4% of the DM-SR reference result. For the SM-SR deviations were explained by poorer spectral resolutions and lower accuracies caused by decreased sensitivities of the photodiode arrays in a wave-length range below 350 nm. For j((OD)-D-1), the results were more complex within +8% and -4% with increasing deviations towards larger solar zenith angles for the SM-SR. The direction and the magnitude of the deviations were dependent on the technique of background determination. All j(NO2))-FR showed good linearity with sing-le calibration factors being sufficient to convert from output voltages to j(NO2)). Measurements were feasible until sunset and comparison with previous calibrations showed good long-term stability. For the j((OD)-D-1)-FR, conversion from output voltages to j((OD)-D-1) needed calibration factors and correction functions considering the influences of total ozone column and elevation of the sun. All instruments showed good linearity at photolysis frequencies exceeding about 10% of maximum values. At larger solar zenith angles, the agreement was non-uniform with deviations explainable by insufficient correction functions. Comparison with previous calibrations for sonic J((OD)-D-1)-FR indicated drifts of calibration factors.
This is a Approved version This version's date is: 10/9/2008 This item is not peer reviewed
https://repository.royalholloway.ac.uk/items/6a9e0d84-ed80-4a5c-c302-91805039a32c/9/
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