Berlin 2005 – wissenschaftliches Programm

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UP: Umweltphysik

UP 3: Atmosph
ärische Spurengase und Aerosole: Intrumentelles I

UP 3.5: Fachvortrag

Montag, 7. März 2005, 15:30–15:45, TU TA201

Tomographic Reconstruction of 2D-Trace Gas Concentration Distributions from Long-path DOAS Measurements: General Approach and Application to an Indoor Validation Experiment — •A. Hartl, K.-U. Mettendorf, B.-C. Song, U. Platt, and I. Pundt — Institut für Umweltphysik, University of Heidelberg

DOAS-Tomography combines DOAS (Differential Optical Absorption Spectroscopy) measurements yielding average concentrations of atmospheric trace gases along long light paths with tomographic methods to retrieve the spatial concentration fields. To investigate the possibility of reconstructing distinct local plumes with only a limited number of light paths (10 to 40), we performed computer simulations with a variable number of Gaussians as test distributions for different peak extensions and for different measurement geometries. Using a discrete approach and iterative projection algorithms from image reconstruction, we show that results heavily depend on peak extensions and that they can be crucially improved in terms of reconstruction errors as well as absolute concentrations by choosing optimal parametrisation. We calculate different contributions to the reconstruction error from discretisation and inversion individually and investigate how they can be further reduced by the recently proposed method "grid translation". Additionally, we discuss the case of a smooth background concentration. Finally, this method is applied to an indoor tomographic DOAS-experiment, including discussion of the effects of measurement errors.