title: Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.
abstract: A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg.
authors.affiliation: Facultad de Ingenieria, Instituto de Física, J. Herrera y Reissig 565, Montevideo, Uruguay. efrins@fing.edy.uy
authors.forename: Erna
authors.initials: E
authors.lastname: Frins
authors.forename: Nicole
authors.initials: N
authors.lastname: Bobrowski
authors.forename: Ulrich
authors.initials: U
authors.lastname: Platt
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner