Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements A. Kylling1, T. Danielsen1, M. Blumthaler2, J. Schreder2, and B. Johnsen3 1Norwegian Institute for Air Research, Kjeller, Norway 2Institute of Medical Physics, University of Innsbruck, Innsbruck, Austria 3Norwegian Radiation Protection Authority, Oslo, Norway
Abstract. A new ligthweight multichannel moderate bandwidth filter instrument
designed to be flown on balloons, is described. The instrument measures the radiation field within the short UV (center wavelength at
312 nm) and long UV (center wavelength at 340 nm). The angular and spectral characteristics of the
instrument are discussed and the calibration procedure outlined. Measurements made during a stratospheric balloon flight
at twilight conditions from Gap-Tallard, France, are presented and compared with state-of-the-art radiative transfer model
simulations. The model simulations and the measurements agree within ±10%
(±20%) for solar zenith angles smaller than 93° (90°) for the 340 (312)
nm channel. Based on the model simulations of the measured radiation, actinic flux spectra are reconstructed. These are used to calculate
various photodissociation rates.
Citation: Kylling, A., Danielsen, T., Blumthaler, M., Schreder, J., and Johnsen, B.: Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements, Atmos. Chem. Phys., 3, 377-385, doi:10.5194/acp-3-377-2003, 2003.