Sub-micrometer aerosol size distribution under natural conditions in the Amazon basin
Poster PDF
Authors
Yang Wang — University of Miami
Florian Ditas — Max Planck Institute for Chemistry
Sophie Louise Mayne — Texas A&M University
Mira Pöhlker — Max Planck Institute for Chemistry
Luciana Rizzo — Universidade Federal de Sao Paulo
Meinrat Andreae — Max Planck Institute of Chemistry
Paulo Artaxo — University of Sao Paulo
Scot T. Martin — Harvard University
Christopher Pohlker — Max Planck Institute for Chemistry
Ulrich Poschl — Max Planck Institute for Chemistry
Courtney Schumacher — Texas A&M University
Jian Wang — Washington University in St. Louis
Category
ARM field campaigns – Results from recent ARM field campaigns
Description
The impact of aerosol on cloud properties represents one of the largest uncertainties in computer simulations of climate change, in large part because of a poor understanding of aerosols under natural conditions that were prevalent during pre-industrial era. The Amazon rainforest is one of the few continental regions where aerosol properties and processes can be studied under near-natural conditions. Here, we present aerosol size distribution and its evolution during the wet season in the Amazon basin using measurements at two background sites, the Amazon Tall Tower Observatory (ATTO) and the ZF2 site upwind of the Manaus city.
Bimodal aerosol size distributions were present in almost all days studied. The separation between the Aitken and accumulation modes suggests an influence of in-cloud processing on the aerosol population. Aitken mode particles are transported from the free troposphere into the boundary layer during precipitation events. The Aitken mode size is negatively correlated with the decrease of the equivalent potential temperature, possibly a result of Aitken mode particles transported from different altitudes in the free troposphere. The concentration of the accumulation mode particles is often the lowest in the early morning, and increases after sunrise. This increase is a combination of (1) mixing of accumulation mode particles in the residue layer aloft down to the surface as boundary layer develops and (2) particle growth through condensation and in-cloud processing. Given the low SO2 concentration under the natural conditions in the Amazon basin, the in-cloud processing of aerosol particles is likely dominated by aqueous phase production of secondary organics from biogenic volatile organic compounds (BVOC).
