Characterization of microphysical properties of Saharan dust aerosols during trans-Atlantic transport

The NOAA Center in Atmospheric Sciences (NCAS) has been studying the trans-Atlantic transport of Saharan dust aerosols since 2001. One of the goals of NCAS was to provide a set of critical measurements to characterize the impacts and microphysical evolution of Saharan dust aerosol during Trans-Atlantic transport. Two land-based and one ship-based intensive observing period (IOP) was performed to characterize the microphysical and chemical properties of Saharan dust. A Laser Particle Counter (LPC) was used to retrieve in-situ number density distribution. A Quartz Crystal Microbalance Cascade Impactor (QCM) was used to retrieve in-situ mass density distributions. The QCM also provides a sampling platform where morphological properties and elemental composition can be determined through post analysis. The combination of the SEM with an Energy Dispersive X-Ray Microanalysis (EDAX) system provides the elemental composition details. The study characterized the dust in terms of aerosol number concentration, mass concentration, particle mean diameter, lognormal number and mass distributions, and surface elemental composition. The aerosol mass concentration peaked in the range between 0.6--3.0 micron while in the dust storm. The aerosol number concentration peaked in the 0.5--1.0 micron size range during the dust storm. A conceptual model for chemical weathering of mineral dust has been developed. The elemental analysis provides a clear picture of dust, smoke and marine particles coinciding with the different regimes we encountered during AEROSE.