Despite the importance of tropospheric ozone (O3) for atmospheric chemistry, air pollution, and climate change, measurements of profiles of the tropospheric O3 concentration are sparse. The Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique has been widely used to derive vertical profiles of trace gases and aerosols in the troposphere. However, tropospheric O3 has not yet been satisfactorily derived from MAX-DOAS measurements due to the influence of stratospheric O3 absorption.
Wang et al.,  developed two new retrieval approaches for tropospheric O3 from MAX-DOAS measurements. In Method 1, stratospheric O3 profiles from external data sources are considered in the retrieval. In Method 2, stratospheric and tropospheric O3 are separated based on the temperature dependent differences between tropospheric and stratospheric O3 absorption structures in the UV spectral range. The feasibility of both retrieval approaches is first verified using synthetic spectra. Then both methods are applied to real measurements. Here, method 1 worked successfully, but method 2 overestimated O3 at altitudes above 1km, probably due to remaining effects of rotational Raman scattering (the so-called Ring effect).
Citation: Wang, Y., Puķīte, J., Wagner, T., Donner, S., Beirle, S., Hilboll, A., et al. . Vertical profiles of tropospheric ozone from MAX‐DOAS measurements during the CINDI‐2 campaign: Part 1—Development of a new retrieval algorithm. Journal of Geophysical Research: Atmospheres, 123. https://doi.org/10.1029/2018JD028647
—Zhanqing Li, Editor, JGR: Atmospheres