Collaborative Research: Gas, Cloudwate, and Rain Hydrogen Peroxide and Methylhydroperoxide Measurements in RICO (Rain in Cumulus Over the Ocean)

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The investigators will contribute to the "Rain in Cumulus over the Ocean" (RICO) experiment by measuring the concentration of hydrogen peroxide and methylhydroperoxide inside and in the vicinity of clouds studied by a research aircraft, the C-130, during flights near Antigua. In combination with other measurements, the measured concentrations will indicate cloud age and the amount of environmental air entrained into the clouds. The broader RICO experiment seeks to study the mechanisms of warm-rain formation, so indications of cloud age can make substantial contributions to the broader experimental objectives by indicating the time available for formation of rain. The study will also characterize the oxidization that occurs in cloud droplets and investigate if substantial production of soluble material occurs as a consequence, causing the residue left upon evaporation of a droplet to be substantially more active as a cloud condensation nucleus than was the original nucleus on which the droplet formed. Furthermore, the two peroxide species are distributed differently in the vertical as a result of precipitation, so their ratio can identify parcels that have been affected by precipitation. These studies will all contribute to better understanding of precipitation processes and the characteristics of trade wind Cumulus clouds.The work will also make important contributions to the training of graduate and undergraduate students and so help develop future capabilities for research in atmospheric chemistry. The techniques to be developed, if shown to be successful, could become important components of future cloud studies. By improving understanding of how oxidation contributes to the growth and modification of cloud condensation nuclei, the project has the potential to help develop a better understanding of the chemical processes that control the microstructure of clouds and hence the interactions of clouds with the climate system.