Pacific Atmospheric Sulfur Experiment

Drexel University, Philadelphia PA

Investigators

Abstract

The Pacific Atmospheric Sulfur Experiment (PASE) is a comprehensive study of the chemistry and physics of sulfur in the remote marine troposphere that will take place near Christmas Island (Kiritimati) in August-September 2007. PASE will focus on gas-phase chemistry, and aerosol composition and growth, in the cloud-free convective boundary layer (CBL), as well as the buffer layer, and the formation of new particles in the cloud outflow of marine cumulus. The flux of dimethyl sulfide (DMS) from the ocean is the major source of sulfur to the remote marine atmosphere and DMS oxidation products are important in aerosol formation and growth. In addition to reflecting incoming solar radiation (the direct effect), aerosols also alter the formation and properties of clouds (indirect effects), which are among the most uncertain processes in climate and global change. PASE will provide information essential for developing an understanding of the aerosol indirect effect in this region. State-of-the-art instrumentation on the NSF C-130 aircraft will be used to make accurate and high speed airborne determinations of sulfur dioxide (SO2), DMS, dimethyl sulfoxide, dimethyl sulfone, methane sulfonic acid, hydroxyl radical, ammonia, water vapor (H2O), ozone (O3), hydrogen peroxide, aerosol size distributions and composition, and meteorological parameters. DMS, SO2, H2O and O3 will be measured at 25 Hz, allowing vertical fluxes of these species to be determined by eddy correlation. Chemical budgets for the sulfur species can be calculated from their concentrations and fluxes. These budgets will contain valuable information on chemistry in general, and on chemical formation and loss rates in particular. PASE is a study of the chemistry underlying aerosol forcing in earth's radiation budget and climate change. The PI will attempt to communicate this through public presentations at the Academy of Natural Sciences in Philadelphia, through the news media, and on a speaker tour to high schools. A web page will be maintained at Drexel University that provides access to the goals and results of PASE for the public. Broader impacts also include the participation of undergraduate and graduate students from Drexel, Georgia Institute of Technology, University of California, Davis, Desert Research Institute/University of Nevada, and the University of Hawaii, who will assist with the field phase of the program and participate in data interpretation, data archiving, and reporting of results.