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UP: Fachverband Umweltphysik
UP 10: Poster: Umweltphysik
UP 10.13: Poster
Donnerstag, 5. März 2009, 17:48–19:00, VMP 9 Poster
Radiative transfer in and around volcanic plumes — •Christoph Kern, Tim Deutschmann, Leif Vogel, Markus Wöhrbach, Matthias Fickel, and Ulrich Platt — Institut für Umweltphysik, Universität Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg
Differential Optical Absorption Spectroscopy (DOAS) is becoming an increasingly popular technique for measuring trace gases such as sulphur dioxide (SO2) and halogen oxides (e.g. BrO, ClO, OClO) in volcanic plumes. Passive DOAS instruments use scattered sunlight as a light source to measure the characteristic absorption structures of the individual trace gases. In order to calculate emission fluxes or plume concentrations from the measured column densities, it is however necessary to determine the light path of the measured photons through the plume. While direct measurement is not possible, several approaches can be made: For one, the known atmospheric concentration of the oxygen dimer O4 allows its absorption to be used as a tracer for atmospheric photon path lengths. Also, broadband analysis of the measured spectra can give insight into Raleigh and Mie scattering processes while the magnitude of the Ring effect can be used as a measure for inelastic Raman scattering. In this study, 3 dimensional radiative transfer modeling was used to gain a quantitative understanding of these effects. The model results of several case studies are discussed. Also the implementation of retrieval algorithms for photon path lengths in and around volcanic plumes is presented.