- 1University of Heidelberg, Institute of Environmental Physics, Heidelberg, Germany
- 2NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 3University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, USA
Characterizing the microphysical properties of aerosols is crucial for understanding their impacts on air quality, climate change, and human health. In this study, we present a novel approach for determining aerosol size distribution, refractive index, and single-scattering albedo using a polarization-sensitive Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument. Extracting the polarimetric state of the atmosphere through polarization-sensitive solar almucantar measurements improves the accuracy and resolution of the derived aerosol parameters.
The RAPSODI retrieval algorithm employs a bimodal size distribution within the aerosol Mie model, coupled with the VLIDORT vector forward model and inversion via the optimal estimation method. Measurements conducted at the IUP Heidelberg during the second half of 2024 provided a dataset of polarization-dependent differential slant column densities (dSCD) and differential slant optical thicknesses (dSOT), which were analyzed to derive the vertical distribution of NO₂, aerosol extinction, and the microphysical properties of the aerosols. Good correlation between measured and modeled dSCDs and dSOTs is achieved, providing confidence that microphysical aerosol parameters can be retrieved reliably with our novel remote sensing method.
The results demonstrate that the polarization-sensitive MAX-DOAS technique improves the information content for characterizing spherical aerosol particles. For validation, we performed comparisons with a co-located CIMEL sun-photometer from the Aerosol Robotic Network (AERONET). This study highlights the potential of polarization-sensitive MAX-DOAS in advancing both data collection and our understanding of aerosol properties.
How to cite: Blohm, K., Frieß, U., Lind, E. S., Tirpitz, J.-L., and Platt, U.: First retrievals of aerosol microphysical properties from polarisation-sensitive MAX-DOAS measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19196, https://doi.org/10.5194/egusphere-egu25-19196, 2025.