Optical and geometrical aerosol particle properties over the United Arab Emirates were assessed

The findings suggest that the mineral dust properties over the Middle East and western Asia, are comparable to those of African mineral dust regarding the particle depolarization ratios, but not the lidar ratios. The smaller lidar ratio compared to reference studies is attributed to the difference in the geochemical characteristics of the soil originating in the study region compared to northern Africa. More specifically, the Arabian dust particle properties are 45 ± 5 (42 ± 5) sr at 355 (532) nm for the lidar ratios, 25 ± 2 % (31 ± 2 %) for the linear particle depolarization ratios at 355 (532) nm, and 0.3 ± 0.2 (0.2 ± 0.2) for the extinction-related Ångström exponent (backscatter-related Ångström exponent) between 355 and 532 nm.

In general, the measurement site was found to be a receptor of frequent dust events, but predominantly the dust is mixed with aerosols of anthropogenic and/or marine origin. The mean aerosol optical depth over the measurement site ranges at 0.37 ± 0.12 and 0.21 ± 0.11 for 355 and 532 nm wavelengths, respectively.

Implications of the incorrect lidar ratio selection is involved in satellite or ground-based extinction profiles (for elastic lidars) and aerosol typing retrievals as well as separation methods of a lidar signal into its aerosol particle components. This becomes evident in stations where they are receptors of both Arabian and Saharan dust and the selection of adequate dust optical parameters is important for further analysis. In turn, the aforementioned products serve as input to advanced methodologies such as the retrieval of CCN/IN concentrations from lidar observations propagating the lidar retrieval errors. Thus, the correct classification of dust types will eventually lead to more accurate techniques for remote observations of this climatically relevant aerosol type.

Further information:

Maria Filioglou, Finnish Meteorological Institute, maria.filioglou@fmi.fi

Filioglou, M., Giannakaki, E., Backman, J., Kesti, J., Hirsikko, A., Engelmann, R., O'Connor, E., Leskinen, J. T. T., Shang, X., Korhonen, H., Lihavainen, H., Romakkaniemi, S., and Komppula, M.: Optical and geometrical aerosol particle properties over the United Arab Emirates, Atmos. Chem. Phys., 20, 8909–8922, https://doi.org/10.5194/acp-20-8909-2020, 2020.