Particle Microphysical-Property Evolution in a North African Dust Plume During Trans-Atlantic Transport

The six-day, trans-Atlantic trajectory of a major North African dust plume in June 2020 provides a unique opportunity to explore the sensitivity of space-based, multi-angle, multi-spectral observations to dust microphysical properties. Recent advances in the optical modeling of non-spherical mineral dust particles make possible more subtle interpretation of the top-of-atmosphere radiances acquired by the NASA Earth Observing System’s Multi-angle Imaging SpectroRadiometer (MISR) instrument. We confirm the MISR radiometrically retrieved aerosol optical depth (AOD), its spectral dependence, and geometrically retrieved plume height, by comparison with published results from other space- and surface-based instruments. But in addition, we use the advanced MISR Research Aerosol retrieval algorithm to produce for the first time a history of changing, column-effective coarse-mode size and light-absorption for non-spherical dust particles during transit. Although the absolute numerical values of particle microphysical properties obtained from remote sensing tend to be qualitative, the stability of the MISR instrument, the dominance of the dust column optical depth contribution throughout the transit in this case, and the darkness and relative uniformity of the underlying ocean surface, lend confidence to the retrieved trends and timescales, though plume heterogeneity, cloud contamination, and in one case sun glint contribute some additional uncertainty to the results. Such constraints offer the promise of using satellite observations beyond AOD to improve the representation of dust-aerosol-related processes in climate models.