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

The NOAA Center in Atmospheric Sciences (NCAS) has been interested in the effects of Saharan dust trans-Atlantic transport since 2001. Intensive observing periods (IOP) were performed in Canary Islands and in Puerto Rico to provide insight of the characteristics of Saharan dust aerosols close to the source and at an endpoint across the Atlantic. The Trans-Atlantic Saharan Dust AERosol and Ocean Science Expedition (AEROSE) 2004 was a 27 day mission aboard the NOAA Ship Ronald H. Brown (RHB). The AEROSE mission took place during February 29th thru March 26th, departing from Barbados to the Canary Islands and ending in Puerto Rico. The cruise tracks for AEROSE 2004 coincided with one of the biggest dust storms to date for this season. One of the goals of the mission was to provide a set of critical measurements to characterize the impacts and microphysical evolution of Saharan dust aerosol during Trans-Atlantic transport. The mission provided the opportunity to connect the data sets obtained at the endpoints by providing the information of the dust aerosols while in the ocean. 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 for post analysis to determine morphological properties and elemental chemical composition. The morphological properties were determined with the use of a Scanning Electron Microscope (SEM). The combination of the SEM with an Energy Dispersive X-Ray Microanalysis system provides the elemental composition details. The data will show the evolution of size-resolved aerosol mass and aerosol number density during one of the major dust storms encountered during the mission. The evolution of the chemical elements as a function of size as they are transported will also be presented. The QCM analysis shows that the aerosol mass density peaked in the range between 0.6 – 3.0 micron while in the dust storm. The aerosol number density peaked in the 0.5 – 1.0 micron size range during the dust storm. The elemental analysis has identified elements such as Fe, Al, Si, Zn, Ti, Co, S, and C all which are characteristics of Saharan dust origin.