Regensburg 2016 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 4: Poster Session
UP 4.5: Poster
Dienstag, 8. März 2016, 16:00–17:30, Foyer H41
On the Impact of Vibrational Raman Scattering of N2/O2 on MAX-DOAS Measurements of Atmospheric Trace Gases — •Johannes Lampel1, Johannes Zielcke2, Udo Frieß2, Ulrich Platt2, and Thomas Wagner1 — 1Max Planck-Institute for Chemistry, Mainz, Germany — 2Institute of Environmental Physics, Heidelberg, Germany
While the first laboratory observation of the Raman effect took place almost 100 years ago, its implications in remote sensing applications, such as the Differential Optical Absorption Spectroscopy (DOAS) of scattered sunlight, still remain under investigation. The main contribution of inelastic scattering is due to rotational Raman scattering, it usually is observed as an additional intensity, leading to filling-in of solar Fraunhofer lines and absorption bands of atmospheric constituents. Measured optical densities are typically corrected for this effect, which is also known as Ring Effect. In contrast to that, Vibrational Raman scattering (VRS) of air was up to now thought to be negligible. We present (1) calculations of vibrational Raman cross-sections of O2 and N2 for passive DOAS measurements and show that consequences of VRS are red-shifted Fraunhofer Ghost Lines (FGL) in scattered light spectra and an additional filling-in of Fraunhofer lines. (2) Based on DOAS measurements during field campaigns, we present first unequivocal observations of FGL at optical densities of up to several 10−4. From our measurements and calculations, we conclude that inclusion of this phenomenon in the spectral evaluation of weak absorbers will lead to considerably more sensitive and precise DOAS measurements.