In the unpolluted air of the Amazon rain forest, the formation of clouds depends on reactions of forest-emitted hydrocarbons with ozone and hydroxyl, in order to generate the aerosols needed as cloud condensation nuclei. Given the relevance of Amazonian convective storms for the local and regional weather, the GoAmazon project was designed to investigate (i) the role of turbulence in the exchanges of gases between the forest and the atmosphere, (ii) the chemical processes related to the photooxidation of biogenic hydrocarbons, and (iii) their impact on aerosol formation. Between March 2014 and January 2015, a 50-m-tall tower was used to collect air turbulence and chemistry data in a region of dense primary forest. In this talk, the field experiment will be presented followed by some initial findings. Data have shown that the frequent passage of convective storms is responsible for significant enhancement of ozone concentrations right above the forest. The interaction between ozone and hydrocarbon molecules, however, depends on the efficiency of turbulent transport within and above the forest. The timescales of the turbulent transport of gases from the region above to a given height inside the canopy can vary from a few minutes to several hours depending on the time of the day. In some cases, these timescales are comparable to ozone deposition and chemical reaction timescales, indicating that these processes can be impacted by the local turbulence intensity. In addition, the residence time of reactive gases emitted within the forest can range from a few seconds to 30 minutes depending on the height of emission and turbulence levels. Finally, it has been observed that right above the forest turbulence can be sustained under more stable conditions than if the forest was not present. In summary, the complex turbulence characteristics of the Amazonian atmosphere likely have an important role in the chemical processes happening in the forest. To help take turbulence into account, simplified models for turbulent transport timescales and air-parcel residence times were developed.
Dr. Livia Freire is a research collaborator at the University of Sao Paulo, Brazil. She has a Ph.D. in Meteorology from The Pennsylvania State University, a M.S. in Numerical Methods for Engineering from Federal University of Parana, Brazil and a B.S in Environmental Engineering from the same university. She is interested in the study of atmospheric turbulence and its role in geophysical and environmental problems, through the use of numerical simulation tools and field data analyses.