Brazil-USA Collaborative Research: Modifications by Anthropogenic Pollution of the Natural Atmospheric Chemistry and Particle Microphysics of the Tropical Rain Forest During the GoAmazon Intensive Operating Periods (IOPs)


  • Henrique Barbosa, University of Sao Paulo
  • Scot Martin, Harvard University
  • Rodrigo Souza, State University of Amazonas


  • FAPESP/DOE/FAPEAM 2013/50510-5

The full project proposal can be download here as a PDF file.


The GoAmazon campaign seeks to quantify and understand how aerosol and cloud life cycles in a particularly clean background in the tropics are influenced by pollutant outflow from a large tropical city, all in the context of addressing the susceptibility of cloud-aerosol-precipitation interactions to present-day and future pollution in the tropics. Within this context of GoAmazon, the overall goals of the proposed research are (i) to measure and mechanistically understand the factors affecting the number-diameter distribution n(d) of the atmospheric particle populationover a tropical rain forest (especially the effects of anthropogenic pollution as a perturbation to natural state) and (ii) to develop and implement an upscaling analysis from this new data set and knowledge of n(d) to prognosticate possible climatic impacts of present-day urban pollution and possibly greater pollution in the future. In relation to these goals, the proposed project has three objectives, as follows:

The first objective is to understand and quantify the interactions of biogenic and anthropogenic emissions with respect to the production of secondary organic aerosol. Hypotheses to be tested are that (i) a shift takes place under anthropogenic conditions in the fate of organic peroxy radicals from HO2 to NO pathways (to be tested by gas-phase analysis by CIMS and PTR-MS; §3.1.3 and §3.1.4) leading to altered rates of particle growth (to be tested by number-diameter distribution measurement of MAOS and AAF; §3.1.1 and §3.1.2), (ii) a significant increase occurs under anthropogenic conditions in the total potential material that can ultimately condense after atmospheric aging to the particle phase (to be tested by the data set of the oxidation flow reactor; §3.1.6) as well as in chemical composition that can influence optical properties and CCN activity (to be tested by the data sets of MAOS and AAF; §3.1.1 and §3.1.2), and (iii) these significant changes in the atmospheric particle population can be monitored regionally by satellite (§3.2.2).

The second objective is to understand and quantify the mechanisms of new particle production over the tropical rain forest, both for natural and anthropogenically influenced conditions. Hypotheses to be tested are that (i) new particle formation occurs above the boundary layer (to be tested by aircraft observations of number-diameter distributions; §3.1.2), (ii) new particles are produced from the evaporation of the jet droplets from fungal spore emission (to be tested by nanoparticle analysis for potassium by the TDCIMS; §3.1.5), and (iii) an absence of sufficient H2SO4 concentration in the gas phase explains the differences for Amazonia compared to other observational sites worldwide (to be tested by gas phase analysis for H2SO4 by CIMS; §3.1.5). These hypotheses will be separately evaluated for conditions when the research site T3 is under influence or not of the plume from Manaus (i.e., natural compared to anthropogenically influenced conditions).

The third objective is to translate the new microphysical knowledge (i.e., as resulting from objectives #1 and #2) into a refined quantitative understanding of the links to climate. Hypotheses to guide the proposed upscaling analyses are that (i) microphysical modeling coupled with aircraft and ground site observations can prognosticate and validate the anthropogenic influence on cloud-aerosol-precipitation interactions associated with the Manaus plume (§3.2.1) and (ii) satellite-based products can be validated by in situ observations and subsequently used to provide a quantitative assessment of the regional effects of Manaus pollution (e.g., such as on direct and indirect radiative forcing, air quality, and human health, with a focus of the funded study on the first of these three; §3.2.2).

The proposed activities and associated three objectives, when taken together as a whole, respond to the Thematic Area of Atmospheric System Research (ASR) of DOE DE-FOA-0000919, FAPESP Chamada FAPESP 21/2013, and FAPEAM EDITAL N. 013/2013. With respect to Science Areas of those calls, the proposal will “improve understanding of the life cycle of aerosols... including the interaction of pristine and polluted air masses” (80% of proposed effort) as well as “improve understanding of the interaction of aerosols and clouds over the Amazon basin, including aerosol impacts on precipitation... as well as cloud impacts on aerosol transport, chemistry, and removal” (20% of proposed effort).