Technical note: Evaluation of profile retrievals of aerosols and trace gases for MAX-DOAS measurements under different aerosol scenarios based on radiative transfer simulations

Abstract. Ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a state-of-the-art remote sensing technique for deriving vertical profiles of trace gases and aerosols. However, MAX-DOAS profile inversions under aerosol pollution scenarios are challenging because the complex radiative transfer limited information content measurements. In this study, performances two inversion algorithms were evaluated various based on synthetic slant column densities (SCDs) derived from simulations. Compared to previous studies, in our much larger ranges optical depth (AOD) NO2 (VCDs) covered. One algorithm optimal estimation; other uses parameterized approach. analysis, three types shapes aerosols considered: exponential, Boltzmann, Gaussian. First, systematic deviations retrieved input investigated. For most cases, AODs found be systematically lower than values, increased with increasing AOD. particular estimation high AOD, these findings consistent results studies. The assumed single scattering albedo (SSA) asymmetry parameter (AP) have influence retrieval. cases SSA AP retrieval rather small (compared uncertainties). algorithm, agreement values can improved by optimizing covariance matrix priori uncertainties. Second, effects tested. Here, especially dependence VCD was found, strong relative overestimation low VCDs an underestimation VCDs. contrast, low. Interestingly, both investigated wavelengths (360 477 nm) similar, indicating that differences between no effect. general, schemes retrieve near-surface extinction gas concentrations well.