EGU2020-10182, updated on 25 Jul 2024
https://doi.org/10.5194/egusphere-egu2020-10182
EGU General Assembly 2020
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

The information content of skylight polarisation in MAX-DOAS trace gas and aerosol profiling applications

Jan-Lukas Tirpitz1, Udo Frieß1, and Ulrich Platt1,2
Jan-Lukas Tirpitz et al.
  • 1Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany (jan-lukas.tirpitz@iup.uni-heidelberg.de)
  • 2Max Planck Institute for Chemistry, Mainz, Germany

Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a well-established ground-based measurement technique for the detection of atmospheric aerosol and trace gases: ultra-violet and visible radiation spectra of skylight are analyzed to obtain information on different atmospheric parameters. An appropriate set of spectra recorded under different viewing geometries ("Multi-Axis") allows retrieval of aerosol and trace gas vertical distributions by applying numerical inversion methods. Currently one of the method’s major limitations is the limited information content in the measurements that reduces the sensitivity particularly at higher altitudes.

It is well known but not yet used in MAX-DOAS profile retrievals that measuring skylight of different polarisation directions provides additional information: the degree of polarisation for instance strongly depends on the atmospheric aerosol content and the aerosol properties and – since the light path (?) differs for light of different polarisation -  the set of geometries available for the inversion is extended. We present a novel polarization-sensitive MAX-DOAS instrument and a corresponding inversion algorithm, capable of using polarization information. Further, in contrast to existing MAX-DOAS algorithms consisting of separate aerosol and trace gas retrieval modules, our novel inversion scheme simultaneously retrieves aerosol and trace gas profiles of several species in a single step. The improvement over “unpolarised” MAX-DOAS approaches will be discussed, based on both, synthetic data and real measurements.

How to cite: Tirpitz, J.-L., Frieß, U., and Platt, U.: The information content of skylight polarisation in MAX-DOAS trace gas and aerosol profiling applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10182, https://doi.org/10.5194/egusphere-egu2020-10182, 2020.