This paper describes 3-hourly radiosonde observations of the Saharan air layer (SAL) acquired from the NOAA Ship Ronald H. Brown during the 2004 Aerosol and Ocean Science Expedition (AEROSE). The sampling frequency allows for unique vertical cross-sectional analyses of SAL phenomena, including dust events detected by shipboard Sun photometers, observed during March 2004. The observational analyses provide, for the first time, a coherent, 2-dimensional space-time depiction of the SAL as an expansive warm, dry, stable column located above the marine boundary layer. Midlevel easterly wind maxima are also observed to occur near the leading edge of the dry layers. The AEROSE sounding data will be useful for studies of the SAL, as well as for validation of environmental satellite sensors, especially the Aqua Atmospheric Infrared Sounder (AIRS).