B129-01
The Vertical Gradient of Aerosols in the Amazonian ATTO Tower: Optical Properties and Size Distributions

Thursday, 17 December 2020: 07:00
Virtual
Marco Aurélio Franco1, Fernando Morais2, Bruna A. Holanda1, Florian Ditas3, Leslie Kremper4, Samara Carbone5, Luciana Varanda Rizzo6, Luiz Machado7, Janaina Mayara Pinto Nascimento8, Milena Ponczeck9, Henrique M Barbosa10, Meinrat O Andreae11, Ulrich Poeschl12, Christopher Pöhlker1 and Paulo Artaxo2, (1)Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany, (2)University of São Paulo, Physics Institute, São Paulo, Brazil, (3)Hessian Agency for Nature Conservation, Environment and Geology, Department for Ambient Air Quality, Wiesbaden, Germany, (4)Max Planck Institut for Chemistry, Multiphase Chemistry Department, Mainz, Germany, (5)University of Sao Paulo, Sao Paulo, United States, (6)Universidade Federal de São Paulo, Departamento de Ciências Exatas e da Terra, Diadema, Brazil, (7)INPE National Institute for Space Research, Sao Jose dos Campos, Brazil, (8)INPA National Institute for Amazonian Research, Manaus, Brazil, (9)University of Sao Paulo, Institute of Physics, Department of Applied Physics, Sao Paulo, Brazil, (10)Instituto de Física, Universidade de São Paulo., São Paulo, Brazil, (11)Max Planck Institute for Chemistry, Biogeochemistry Department, Mainz, Germany, (12)Max Planck Institute for Chemistry, Mainz, Germany
Recorded Presentation
Abstract:
The atmosphere-biosphere interactions in Central Amazonia is a complex nonlinear dynamic system, highly effective in the exchange of particles and trace gases. The Amazonian Tall Tower Observatory (ATTO) is a unique laboratory that allows analysis of aerosol along the vertical profile (VP) up to 325m high, located in an undisturbed forest region. This study analyses measurements of the VP of dry aerosol optical properties (AOP) and size distributions (SD) at two different heights at ATTO: 60 and 325 m, in the wet season of 2019. It was observed that the median scattering coefficient at 550 nm was higher at 60 m (10.3 Mm-1) than at 325 m (7.7 Mm-1). On the other side, the absorption coefficient at 637 nm was higher at 325 m (0.82 Mm-1) than at 60 m (0.54 Mm-1). The single-scattering albedo indicates that aerosols are more absorbing at 325 m, with medians of 0.94 and 0.87 for 60 and 325 m, respectively, which is a significant difference. It indicates that at 60 m canopy level the aerosol is mostly controlled by the vegetation, while at 325m it is more influenced by long range transport (LRT) from Africa. In general, particles are smaller at 60 m than at 325 m. This is corroborated by both scattering Ångström exponent (SAE) analysis and SD measurements. The SAE is higher at 60 m, with median values around 1.4, while at 325 m, it is 1.1. It happens because primary biogenic particles are more abundant close to the canopy. Aging could partially explain the SD differences in the accumulation mode, with median values of 150 nm at 60 m and 170 nm at 325 m, and total median particle concentration of 292 and 264 cm-3, at 60 and 325 m, respectively. It is observed two types of episodic particle size distribution events: burst-like (BL) and growth-like (GL) events. GL have shown to be significantly different from similar events in boreal forests, with GL starting at 30-40 nm, which is much larger than what has been reported. Also, there is a clear relation of particle events and convective precipitation with strong downdrafts. BL-GL events, in addition to AOP, indicates complex mechanisms of production and transport of aerosols within the boundary layer in the wet season. The mechanisms influencing aerosol population in the Amazonian boundary layer may be: a) LRT of aerosol plumes; b) downdrafts of the upper troposphere and c) BVOC/SOA production close to the forest canopy.
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