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Modeling evolution of aerosol size distribution in the Manaus urban plume during the GoAmazon campaign

 
Poster PDF

Authors

Rahul Zaveri — Pacific Northwest National Laboratory
Jian Wang — Washington University in St. Louis
John E Shilling — Pacific Northwest National Laboratory
Scot T. Martin — Harvard University
Paulo Artaxo — University of Sao Paulo
Luiz Augusto Toledo Machado — INPE-CPTEC
Karla Longo — National Institute for Space Research (INPE)
Ed Fortner — Aerodyne Research, Inc.
Mikhail S. Pekour — Pacific Northwest National Laboratory
Jason Tomlinson — Pacific Northwest National Laboratory
Fan Mei — Pacific Northwest National Laboratory
Duli Chand — Pacific Northwest National Laboratory
John Hubbe — Pacific Northwest National Laboratory
Stephen R. Springston — Brookhaven National Laboratory

Category

Secondary organic aerosol

Description

As part of the Green Ocean Amazon (GoAmazon) field campaign in Brazil, the DOE G-1 aircraft was deployed to make semi-Lagrangian measurements of aerosols and trace gases over and downwind of Manaus, with the objective of investigating the interaction of urban emissions with natural emissions from the surrounding pristine rainforest. Here we focus on the evolution of aerosol size distribution in the Manaus plume on March 13th, 2014. On this day, there was a clear enhancement of both Aitken mode (diameter ~15 nm) and accumulation mode (diameter ~150 nm) aerosols over Manaus relative to the background. The Aitken mode aerosol was found to progressively grow in the urban plume at increasing downwind distances from Manaus while the accumulation mode diameter remained nearly constant with aging. At the same time, the accumulation mode organic aerosol (OA) mean carbon oxidation state was found to increase as the plume aged, although the ratio of excess OA mass to excess CO remained nearly constant with aging. The comprehensive sectional aerosol box model MOSAIC is applied to interpret the observed evolution of aerosol size distribution and the associated optical and cloud condensation nuclei properties, and gain insights into the mechanisms of secondary organic aerosol formation and growth in the Manaus plume. The roles of coagulation and condensation will be evaluated in shaping the aerosol size distribution with time.