Atmospheric measurements aboard C-130 during the Pacific Atmospheric Sulfur Experiment

The Pacific Atmospheric Sulfur Experiment (PASE) is a study with a primary goal aimed at understanding the sulfur cycle in a remote marine atmosphere. The study will be conducted in August and September months of 2007 at Christmas Island on board the NSF/NCAR C-130 aircraft. It will foremost focus on measurements of DMS (dimethyl sulfide) and its contribution to formation of H2SO4 (sulfuric acid) and MSA (methane-sulfonic acid) by reaction with OH (hydroxyl). PASE will also concentrate on subsequent production of aerosols and cloud condensation nuclei from H2SO4, MSA, and NH3 concentrations in a cloud free convective boundary layer (CBL) and in outflow of marine cumulus. This paper explains the measurement technique for OH, H2SO4, MSA, HO2, HO2+RO2 (peroxy radicals), and NH3 (ammonia) using the SICIMS (Selected ion chemical ionization mass spectrometer). It also presents sample measurements from test flights of OH, H2SO4, MSA, HO2, and HO2+RO2. In addition, this paper discusses the measurement technique utilized aboard the C-130 in testing SO2, DMS, DMSO (dimethyl sulfoxide), DMSO2 (dimethyl sulfone), O3 (ozone), aerosols, and cloud condensation nuclei. It includes several adaptations to technique and instrumentation from previous studies conducted: the First Aerosol Characterization Experiment (ACE-1) in 1998, the Pacific Exploratory Missions A and B (PEM-Tropics) in 1996, and the Intercontinental Transport Experiment (INTEX-B) in 2006. The Significant Opportunities in Atmospheric Research and Science (SOARS) Program is managed by the University Corporation for Atmospheric Research (UCAR) with support from participating universities. SOARS is funded by the National Science Foundation, the National Oceanic and Atmospheric Administration (NOAA) Climate Program Office, the NOAA Oceans and Human Health Initiative, the Center for Multi-Scale Modeling of Atmospheric Processes at Colorado State University, and the Cooperative Institute for Research in Environmental Sciences. SOARS also receives funding from the National Center for Atmospheric Research (NCAR). SOARS is a partner project with Research Experience in Solid Earth Science for Student (RESESS).