The NOAA (National Oceanic and Atmospheric Administration) Pacific Marine Environmental Laboratory's aerosol research program is focused on the impact of atmospheric particulates on climate and air quality. Our approach is to characterize relevant aerosol chemical, physical, and optical properties using a combination of in situ and remote instrumentation and optical models. The resulting data base includes long term measurements from northern hemisphere aerosol monitoring stations operated by NOAA and short term measurements from international intensive aerosol experiments. The data provide information on spatial and temporal means and variability in aerosol properties and on aerosol formation and transformation processes in the boundary layer. To demonstrate our in situ measurement and modeling capabilities, results are presented here from ACE Asia, an experiment we participated in during the spring of 2001.