The NOAA Center in Atmospheric Sciences (NCAS) Trans-Atlantic Saharan Dust AERosol and Ocean Science Expedition (AEROSE) 2004 was a 27 day mission aboard the NOAA Ship Ronald H. Brown (RHB) that took place during February 29th thru March 26th, 2004. The cruise tracks for AEROSE 2004 coincided with one of the biggest dust storms to date for this season. In-situ measurements of size-fractionated aerosol mass and number density distribution were performed during AEROSE. A Quartz Crystal Microbalance Cascade Impactor (QCM) and a Laser Particle Counter (LPC) was used to retrieve the mass and number density distributions. We will present data showing the evolution of size-resolved aerosol mass and number distribution during a case study dust storm event.