Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 2 1 2009 10.5194/amtd-2-87-2009 http://www.atmos-meas-tech-discuss.net/2/87/2009/ http://www.atmos-meas-tech-discuss.net/2/87/2009/amtd-2-87-2009.html http://www.atmos-meas-tech-discuss.net/2/87/2009/amtd-2-87-2009.pdf 87 118 2009-01-14 A new method for the simulation of the Ring effect in observations of scattered sun light T. Wagner thomas.wagner@mpch-mainz.mpg.de S. Beirle T. Deutschmann Max-Planck-Institute for Chemistry, Mainz, Germany Institut für Umweltphysik, University of Heidelberg, Heidelberg, Germany We present a new technique for the quantitative simulation of the "Ring effect" for scattered light observations from various platforms and under different atmospheric situations. The method is based on radiative transfer calculations at only one wavelength λ₀ in the wavelength range under consideration, and is thus computationally fast. The strength of the Ring effect is calculated from statistical properties of the photon paths for a given situation, which makes Monte Carlo radiative transfer models in particular appropriate. We quantify the Ring effect by the so called rotational Raman scattering probability, the probability that an observed photon has undergone a rotational Raman scattering event. The Raman scattering probability is independent from the spectral resolution of the instrument and can easily be converted into various definitions used to characterise the strength of the Ring effect. We compare the results of our new method to the results of previous studies and in general good quantitative agreement is found. 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