Browsing by Author "Schumacher, Courtney"

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Downward transport of ozone rich air & implications for atmospheric chemistry in the Amazon rainforest
(2016-01) Gerken, Tobias; Wei, Dandan; Chase, Randy J.; Fuentes, Jose D.; Schumacher, Courtney; Machado, Luiz A.; Andreoli, Rita V.; Chamecki, Marcelo; Ferreira de Souza, Rodrigo A.; Freire, Livia S.; Jardine, Angela B.; Manzi, Antonio O.; Nascimento dos Santos, Rosa M.; von Randow, Celso; dos Santos Costa, Patricia; Stoy, Paul C.; Tota, Julio; Trowbridge, Amy M.
From April 2014 to January 2015, ozone (O3) dynamics were investigated as part of GoAmazon 2014/5 project in the central Amazon rainforest of Brazil. Just above the forest canopy, maximum hourly O3 mixing ratios averaged 20 ppbv (parts per billion on a volume basis) during the June–September dry months and 15 ppbv during the wet months. Ozone levels occasionally exceeded 75 ppbv in response to influences from biomass burning and regional air pollution. Individual convective storms transported O3-rich air parcels from the mid-troposphere to the surface and abruptly enhanced the regional atmospheric boundary layer by as much as 25 ppbv. In contrast to the individual storms, days with multiple convective systems produced successive, cumulative ground-level O3 increases. The magnitude of O3 enhancements depended on the vertical distribution of O3 within storm downdrafts and origin of downdrafts in the troposphere. Ozone mixing ratios remained enhanced for > 2 h following the passage of storms, which enhanced chemical processing of rainforest-emitted isoprene and monoterpenes. Reactions of isoprene and monoterpenes with O3 are modeled to generate maximum hydroxyl radical formation rates of 6 × 106 radicals cm−3s−1. Therefore, one key conclusion of the present study is that downdrafts of convective storms are estimated to transport enough O3 to the surface to initiate a series of reactions that reduce the lifetimes of rainforest-emitted hydrocarbons.
Linking meteorology, turbulence, and air chemistry in the Amazon Rain Forest
(2016-12) Fuentes, Jose D.; Chamecki, Marcelo; Nascimento dos Santos, Rosa Maria; von Randow, Celso; Stoy, Paul C.; Katul, Gabriel; Fitzjarrald, David; Manzi, Antonio O.; Gerken, Tobias; Trowbridge, Amy M.; Freire, Livia Souza; Ruiz-Plancarte, Jesus; Furtunato Maia, Jair Max; Tota, Julio; Dias, Nelson; Fisch, Gilberto; Schumacher, Courtney; Acevedo, Otavio C.; Mercer, Juliane Rezende; Yanez-Serrano, Ana Maria
We describe the salient features of a field study whose goals are to quantify the vertical distribution of plant-emitted hydrocarbons and their contribution to aerosol and cloud condensation nuclei production above a central Amazonian rain forest. Using observing systems deployed on a 50-m meteorological tower, complemented with tethered balloon deployments, the vertical distribution of hydrocarbons and aerosols was determined under different boundary layer thermodynamic states. The rain forest emits sufficient reactive hydrocarbons, such as isoprene and monoterpenes, to provide precursors of secondary organic aerosols and cloud condensation nuclei. Mesoscale convective systems transport ozone from the middle troposphere, enriching the atmospheric boundary layer as well as the forest canopy and surface layer. Through multiple chemical transformations, the ozone-enriched atmospheric surface layer can oxidize rain forest-emitted hydrocarbons. One conclusion derived from the field studies is that the rain forest produces the necessary chemical species and in sufficient amounts to undergo oxidation and generate aerosols that subsequently activate into cloud condensation nuclei.