Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 2: Variability and characteristic differences under near-pristine, biomass burning, and long-range transport conditions

Abstract

Size-resolved measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a full seasonal cycle (Mar 2014 -Feb 2015. In a companion part 1 paper, we presented an in-depth CCN characterization based on annually as well as seasonally averaged time intervals and discuss different para-5 metrization strategies to represent the Amazonian CCN cycling in modelling studies (M. Pöhlker et. al. 2016b).The present part 2 study analyzes the aerosol and CCN variability in original time resolution and, thus, resolves aerosol advection and transformation for the following case studies, which represent the most characteristic states of the Amazonian atmosphere: ), a mostly organic particle composition, and relatively low hygroscopicity levels (κAit = 0.12 vs. κacc = 0.18). The NP CCN efficiency spectrum shows that the CCN population is sensitive to changes in supersaturation (S) over a wide S range. Atmos. Chem. Phys. Discuss., https://doi

Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

“…Wang et al, 2016). In contrast, ACRIDICON-CHUVA took place during the dry season, when the Amazon Basin is impacted by a mixture of pollution from regional and remote sources Talbot et al, 1988;Artaxo et al, 2013;Pöhlker et al, 2017). Deforestation and pasture maintenance burning occurs throughout the basin, with the highest intensity along the southern periphery, the so-called "arc of deforestation".…”

Long-term study on coarse mode aerosols in the Amazon rain forest with the frequent intrusion of Saharan dust plumes

“…In fact, the Amazon has been ranked as one of the potential tipping points in the global climate system (Lenton et al, 2008). Furthermore, it represents a unique location to study the human influence on the atmosphere as it represents one of the few remaining continental places where episodes with a nearpristine atmospheric state can be found (Andreae, 2007;Martin et al, 2010a;Pöschl et al, 2010).…”

“…Coarse mode aerosols play several important roles in the rain forest ecosystem. They can act as ice nuclei (i.e., bioaerosol particles that are ice-active at high temperatures) and giant cloud condensation nuclei in aerosol-cloud interaction (Prenni et al, 2009;Pöschl et al, 2010). The advected Saharan dust particles, which mostly occur in the coarse mode, are regarded as important fertilizers for the comparably poor Amazonian soils (e.g., by bringing iron and phosphorous) (Swap et al, 1992;Rizzolo et al, 2017).…”

“…The majority of aerosol studies from the Amazon Basin has focused on the life cycle and processing of the submicron size range of the aerosol population and its relevance for the Earth's climate system (Martin et al, 2010b;Artaxo et al, 2013a;Andreae et al, 2015Andreae et al, , 2018. Its seasonal variability, superimposed on a background of biogenic, mostly secondary organic aerosol (Pöschl et al, 2010), is largely governed by the extent of biomass burning activities in Africa and South America as well as the transport patterns of the emitted aerosols. Accordingly, the anthropogenic impact on the fine mode aerosol, including its links to biogeochemical and hydrological cycling, is particularly pronounced.…”

African volcanic emissions influencing atmospheric aerosol particles over the Amazon rain forest

“…Usually with a maximum of 0.36. The Nya2014 κ average was slightly higher than the 2014 dry season average of 0.21 ± 0.03 for 0.10 % supersaturation (excluding the volcanic event), and significantly higher than a strong BB event average of 0.18 ± 0.01 for 0.10 % supersaturation, whose high OA content (sulfate-to-OA < 0.04) caused a significant drop in the hygroscopicity parameter (Pöhlker et al, 2017b).…”