scholarly journals 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

2017 ◽  
Author(s):  
Mira L. Pöhlker ◽  
Florian Ditas ◽  
Jorge Saturno ◽  
Thomas Klimach ◽  
Isabella Hrabě de Angelis ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Amazon Basin ◽  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Aerosol Cloud ◽  
Amazon Rain Forest ◽  
Depth Analysis ◽  
Modelling Studies ◽  
Original Time ◽  
Aerosol Emissions

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 parametrization 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: 1. Near-pristine (NP) conditions, defined as the absence of detectable black carbon ( 90 %), and correspondingly low hygroscopicity levels (κAit = 0.14, κacc = 0.17). The BB CCN efficiency spectrum shows that the CCN population is highly sensitive to changes in S in the low S regime. 4. Mixed pollution conditions show the superposition of African (i.e., volcanic) and Amazonian (i.e., biomass burning) aerosol emissions during the dry season. The African aerosols showed a broad monomodal distribution (D = 130 nm, N = ~ 1300 cm−3), with very high sulfate fractions (20 %), and correspondingly high hygroscopicity (κAit = 0.14, κacc = 0.22). This was superimposed by fresh smoke from nearby fires with one strong mode (D = 113 nm, Nacc = ~ 2800 cm−3), an organic-dominated aerosol, and sharply decreased hygroscopicity (κAit = 0.10, κacc = 0.20). These conditions underline the rapidly changing pollution regimes with clear impacts on the aerosol and CCN properties. Overall, this study provides detailed insights into the CCN cycling in relation to aerosol-cloud interaction in the vulnerable and climate-relevant Amazon region. The detailed analysis of aerosol and CCN key properties and particularly the extracted CCN efficiency spectra with the associated fit parameters provide a basis for an in-depth analysis of aerosol-cloud interaction in the Amazon and beyond.

scholarly journals The challenge of simulating the sensitivity of the Amazonian cloud microstructure to cloud condensation nuclei number concentrations

2020 ◽  
Vol 20 (3) ◽  
pp. 1591-1605 ◽  
Author(s):  
Pascal Polonik ◽  
Christoph Knote ◽  
Tobias Zinner ◽  
Florian Ewald ◽  
Tobias Kölling ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Effective Radius ◽  
Cloud Base ◽  
Atmospheric Conditions ◽  
Condensation Nuclei ◽  
Aerosol Cloud

Abstract. The realistic representation of aerosol–cloud interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon region has been one of the motivations for several field campaigns, including the airborne “Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA)” campaign based in Manaus, Brazil, in September 2014. In this work we combine in situ and remotely sensed aerosol, cloud, and atmospheric radiation data collected during ACRIDICON-CHUVA with regional, online-coupled chemistry-transport simulations to evaluate the model's ability to represent the indirect effects of biomass burning aerosol on cloud microphysical and optical properties (droplet number concentration and effective radius). We found agreement between the modeled and observed median cloud droplet number concentration (CDNC) for low values of CDNC, i.e., low levels of pollution. In general, a linear relationship between modeled and observed CDNC with a slope of 0.3 was found, which implies a systematic underestimation of modeled CDNC when compared to measurements. Variability in cloud condensation nuclei (CCN) number concentrations was also underestimated, and cloud droplet effective radii (reff) were overestimated by the model. Modeled effective radius profiles began to saturate around 500 CCN cm−3 at cloud base, indicating an upper limit for the model sensitivity well below CCN concentrations reached during the burning season in the Amazon Basin. Additional CCN emitted from local fires did not cause a notable change in modeled cloud droplet effective radii. Finally, we also evaluate a parameterization of CDNC at cloud base using more readily available cloud microphysical properties, showing that we are able to derive CDNC at cloud base from cloud-side remote-sensing observations.

scholarly journals Cloud condensation nuclei activity of fresh primary and aged biomass burning aerosol

2012 ◽  
Vol 12 (15) ◽  
pp. 7285-7293 ◽  
Author(s):  
G. J. Engelhart ◽  
C. J. Hennigan ◽  
M. A. Miracolo ◽  
A. L. Robinson ◽  
S. N. Pandis
Keyword(s):  
Biomass Burning ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Condensation Nuclei ◽  
Hygroscopic Properties ◽  
A Value ◽  
Biomass Burning Aerosol ◽  
Photochemical Processing ◽  
Photochemical Aging ◽  
Aerosol Emissions

Abstract. We quantify the hygroscopic properties of particles freshly emitted from biomass burning and after several hours of photochemical aging in a smog chamber. Values of the hygroscopicity parameter, κ, were calculated from cloud condensation nuclei (CCN) measurements of emissions from combustion of 12 biomass fuels commonly burned in North American wildfires. Prior to photochemical aging, the κ of the fresh primary aerosol varied widely, between 0.06 (weakly hygroscopic) and 0.6 (highly hygroscopic). The hygroscopicity of the primary aerosol was positively correlated with the inorganic mass fraction of the particles. Photochemical processing reduced the range of κ values to between 0.08 and 0.3. The changes in κ were driven by the photochemical production of secondary organic aerosol (SOA). SOA also contributed to growth of particles formed during nucleation events. Analysis of the nucleation mode particles enabled the first direct quantification of the hygroscopicity parameter κ for biomass burning SOA, which was on average 0.11, similar to values observed for biogenic SOA. Although initial CCN activity of biomass burning aerosol emissions are highly variable, after a few hours of photochemical processing κ converges to a value of 0.2 ± 0.1. Therefore, photochemical aging reduces the variability of biomass burning CCN κ, which should simplify analysis of the potential effects of biomass burning aerosol on climate.

scholarly journals Cloud condensation nuclei activity of fresh primary and aged biomass burning aerosol

2012 ◽  
Vol 12 (3) ◽  
pp. 7521-7544 ◽  
Author(s):  
G. J. Engelhart ◽  
C. J. Hennigan ◽  
M. A. Miracolo ◽  
A. L. Robinson ◽  
S. N. Pandis
Keyword(s):  
Biomass Burning ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Condensation Nuclei ◽  
Hygroscopic Properties ◽  
A Value ◽  
Biomass Burning Aerosol ◽  
Photochemical Processing ◽  
Photochemical Aging ◽  
Aerosol Emissions

Abstract. We quantify the hygroscopic properties of particles freshly emitted from biomass burning and after several hours of photochemical aging in a smog chamber. Values of the hygroscopicity parameter, κ, were calculated from cloud condensation nuclei (CCN) measurements of emissions from combustion of 12 biomass fuels commonly burned in North American wildfires. Prior to photochemical aging, the κ of the fresh primary aerosol varied widely, between 0.06 (weakly hygroscopic) and 0.6 (highly hygroscopic). The hygroscopicity of the primary aerosol was positively correlated with the inorganic mass fraction of the particles. There was also a relationship between the hygroscopicity of the primary aerosol and the extent of oxygenation of the primary organic aerosol (POA), suggesting an influence of the POA composition on the primary aerosol hygroscopicity as well. Photochemical processing reduced the range of κ values to between 0.08 and 0.3. The changes in κ were driven by the photochemical production of secondary organic aerosol (SOA). SOA also contributed to growth of particles formed during nucleation events. Analysis of the nucleation mode particles enabled the first direct quantification of the hygroscopicity parameter κ for biomass burning SOA, which was on average 0.11, similar to values observed for biogenic SOA. Although initial CCN activity of biomass burning aerosol emissions are highly variable, after a few hours of photochemical processing κ converges to a value of 0.2 ± 0.1. Therefore, photochemical aging reduces the variability of biomass burning CCN, which should simplify analysis of the potential effects of biomass burning aerosol on climate.

A study on aerosol-cloud condensation nuclei (CCN) activation over eastern Himalaya in India

2017 ◽  
Vol 189 ◽  
pp. 69-81 ◽  
Author(s):  
Arindam Roy ◽  
Abhijit Chatterjee ◽  
Chirantan Sarkar ◽  
Sanat Kumar Das ◽  
Sanjay Kumar Ghosh ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Eastern Himalaya ◽  
Condensation Nuclei ◽  
Aerosol Cloud

scholarly journals Influx of African biomass burning aerosol during the Amazonian dry season through layered transatlantic transport of black carbon-rich smoke

2019 ◽  
Author(s):  
Bruna A. Holanda ◽  
Mira L. Pöhlker ◽  
Jorge Saturno ◽  
Matthias Sörgel ◽  
Jeannine Ditas ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Amazon Basin ◽  
Hydrological Cycle ◽  
Atmospheric Transport ◽  
Cloud Condensation Nuclei ◽  
Single Scattering ◽  
Brazilian Coast ◽  
Strong Impact ◽  
The North

Abstract. Black carbon (BC) aerosols are influencing the Earth’s atmosphere and climate, but their microphysical properties, spatiotemporal distribution and long-range transport are not well constrained. This study analyzes the transatlantic transport of BC-rich African biomass burning (BB) pollution into the Amazon Basin, based on airborne observations of aerosol particles and trace gases in and off the Brazilian coast during the ACRIDICON-CHUVA campaign in September 2014, combining in-situ measurements on the research aircraft HALO with satellite remote-sensing and numerical model results. During flight AC19 over land and ocean at the Brazilian coastline in the northeast of the Amazon Basin, we observed a BC-rich atmospheric layer at ~ 3.5 km altitude with a vertical extension of ~ 0.3 km. Backward trajectory analyses suggest that fires in African grasslands, savannas, and shrublands were the main source of this pollution layer, and that the observed BB smoke had undergone more than 10 days of atmospheric transport and aging. The BC mass concentrations in the layer ranged from 0.5 to 2 μg m−3, and the BC particle number fraction of ~ 40 % was about 8 times higher than observed in a fresh Amazonian BB plume, representing the highest value ever observed in the region. Upon entering the Amazon Basin, the layer started to broaden and to subside, due to convective mixing and entrainment of the BB aerosol into the boundary layer. Satellite observations show that the transatlantic transport of pollution layers is a frequently occurring process, seasonally peaking in August/September. By analyzing the aircraft observations within the broader context of the long-term data from the Amazon Tall Tower Observatory (ATTO), we found that the transatlantic transport of African BB smoke layers has a strong impact on the north-central Amazonian aerosol population during the BB-influenced season (July to November). Specifically, the early BB season in this part of the Amazon appears to be dominated by African smoke, whereas the later BB season appears to be dominated by South American fires. This dichotomy is reflected in pronounced changes of aerosol optical properties such as the single scattering albedo (increasing from 0.85 in August to 0.90 in November) and the BC-to-CO enhancement ratio (decreasing from 7.4 to 4.4 ng m−3 ppb−1). Our results suggest that, despite the high amount of BC particles, the African BB aerosol act as efficient cloud condensation nuclei (CCN) with potentially important implications for aerosol-cloud interactions and the hydrological cycle in the Amazon Basin.

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