Measurement of Inorganic Bromine during CONTRAST (CONvective TRansport of Active Species in the Tropics)

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As part of the larger CONTRAST measurement campaign (Convective Transport of Active Species in the Tropics) which has a main objective of measuring the transport of reactive chemical species into the topical Tropopause Transition Layer (TTL) over the western Pacific warm pool, Georgia Tech researchers will measure a number of short lived reactive bromine compounds (BrO, BrCl, the sum of Br2 and HOBr), and also pernitric acid (HO2NO2). These molecules will be detected and quantitated using a chemical ionization mass spectrometer (CIMS) flown on the NSF G-V research aircraft during CONTRAST.During northern winter, surface tropospheric air masses containing these reactive species may be transported by intense tropical convection high into the TTL lower stratosphere over the Pacific warm pool. Here they may substantially impact the chemistry of the lower stratosphere, including its ozone chemistry. Accordingly, knowing the sources, chemical environment and abundance of reactive halogen and short lived halogen containing species such as bromocarbons in the TTL will help inform our understanding of the bromine chemistry of this understudied region of the earth's atmosphere. The observation of pernitric acid, which provides constraint on HOx-NOx radical reactivity, will be modeled photochemically providing an additional test for our understanding of how TTL photochemistry may be impacted by tropical deep convection. The unique low-ozone environments in the upper troposphere are expected to result in very small levels of OH radicals, which can be expected to increase the lifetime of reactive gases whose main loss is through OH radical oxidation. The simultaneous occurrence of deep convection and prolonged lifetime of organic compounds in the TTL can have significant impact on the stratospheric halogen budget.With field work based out of Guam, the project will support one Ph.D. student and provide the bulk of her thesis research work. In addition, one undergraduate student will be provided with an extensive research experience. The timing of the CONTRAST experiment has been designed to take advantage of collaborations with two international airborne studies planned for the same time and geographic location. These are the NASA EV1 project ATTREX (Airborne Tropical Tropopause Experiment) and the European CAST (Coordinated Airborne Studies in the Tropics). With complementary instrument payloads, coordinated flights of the NSF GV, the NASA Global Hawk and the UK BAE146 will provide an unprecedented examination of the full atmospheric column, from surface to 19 km, in the Tropical Western Pacific.