External Mixing Research Articles

Photopolarimetric Sensitivity to Black Carbon Content of Wildfire Smoke: Results From the 2016 ImPACT‐PM Field Campaign

AbstractDetailed characterization of the aerosol content of wildfire smoke plumes is typically performed through in situ aircraft observations, which have limited temporal and spatial coverage. Extending such observations to regional or global scales requires new remote sensing approaches, such as retrievals that make use of spectropolarimetric, multiangle imaging. In this work measurements made during the Imaging Polarimetric Assessment and Characterization of Tropospheric Particulate Matter (ImPACT‐PM) field campaign in a smoke plume near the town of Lebec in Southern California by the Navy Center for Interdisciplinary Remotely Piloted Aircraft Studies Twin Otter aircraft on 8 July 2016 are used in conjunction with near‐coincident measurements from the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) on the National Aeronautics and Space Administration ER‐2 high‐altitude research aircraft to assess the sensitivity of spectropolarimetric measurements to the black carbon content of the plume. Tracking visible features in the smoke through the sequence of AirMSPI observations allowed the height of the plume to be estimated through geometric techniques. Then, by constraining the fractional amounts of the aerosol constituents with the in situ data, radiative closure was obtained through simulations performed with a polarimetric radiative transfer code, demonstrating the ability to constrain the black carbon mass fraction to approximately 5%, given the uncertainties in the AirMSPI measurements and the assumption of external mixing of aerosol components. The AirMSPI retrieval, made using a limited set of observations from the 470 nm polarimetric spectral band alone, was also generally consistent with operational retrievals of aerosol optical depth and surface reflectance made by the Multi‐Angle Implementation of Atmospheric Correction algorithm at 1 km resolution.

Code Switching and Code Mixing in Critical Eleven Novel by Ika Natassa

<em>Code switching and code mixing are the strategy of adapting two languages in a speech. The objective of this research is to find the reason why the characters switch or mix their speaking. Revealing and classifying the kinds of code switching and code mixing are also the aim of this study. The writer chooses novel as the object of this study because the characters of this novel are bilingual who are able to speak more than one language. The type of this research is library research. Therefore, in conducting this journal, descriptive qualitative is used as the method of the analysis. The writer collects data by reading the novel, and marking them to make it easier to analyze. The result of this research points out that code mixing is frequently used by the character in the novel. The writer has collected about five kinds of code switching externally and ten kinds of code mixing. Further result, they are five kinds of internal code mixing, and five kinds of external code mixing, and the rest, there are five of external code switching. They tend to choose lexical items that are appropriate from the language where their repertoire is more comprehensive</em>

Impact of Grain Shape and Multiple Black Carbon Internal Mixing on Snow Albedo: Parameterization and Radiative Effect Analysis

AbstractWe quantify the effects of grain shape and multiple black carbon (BC)‐snow internal mixing on snow albedo by explicitly resolving shape and mixing structures. Nonspherical snow grains tend to have higher albedos than spheres with the same effective sizes, while the albedo difference due to shape effects increases with grain size, with up to 0.013 and 0.055 for effective radii of 1,000 μm at visible and near‐infrared bands, respectively. BC‐snow internal mixing reduces snow albedo at wavelengths < ~1.5 μm, with negligible effects at longer wavelengths. Nonspherical snow grains show less BC‐induced albedo reductions than spheres with the same effective sizes by up to 0.06 at ultraviolet and visible bands. Compared with external mixing, internal mixing enhances snow albedo reduction by a factor of 1.2–2.0 at visible wavelengths depending on BC concentration and snow shape. The opposite effects on albedo reductions due to snow grain nonsphericity and BC‐snow internal mixing point toward a careful investigation of these two factors simultaneously in climate modeling. We further develop parameterizations for snow albedo and its reduction by accounting for grain shape and BC‐snow internal/external mixing. Combining the parameterizations with BC‐in‐snow measurements in China, North America, and the Arctic, we estimate that nonspherical snow grains reduce BC‐induced albedo radiative effects by up to 50% compared with spherical grains. Moreover, BC‐snow internal mixing enhances the albedo effects by up to 30% (130%) for spherical (nonspherical) grains relative to external mixing. The overall uncertainty induced by snow shape and BC‐snow mixing state is about 21–32%.

On Effective Radiative Forcing of Partial Internally and Externally Mixed Aerosols and Their Effects on Global Climate

AbstractThe total effective radiative forcing (ERF) due to partial internally mixed (PIM) and externally mixed (EM) anthropogenic aerosols, as well as their climatic effects since the year of 1850, was evaluated and compared using the aerosol‐climate online coupled model of BCC_AGCM2.0_CUACE/Aero. The influences of internal mixing (IM) on aerosol hygroscopicity parameter, optical properties, and concentration were considered. Generally, IM could markedly weaken the negative ERF and cooling effects of anthropogenic aerosols. The global annual mean ERF of EM anthropogenic aerosols from 1850 to 2010 was −1.87 W m−2, of which the aerosol‐radiation interactive ERF (ERFari) and aerosol‐cloud interactive ERF (ERFaci) were −0.49 and −1.38 W m−2, respectively. The global annual mean ERF due to PIM anthropogenic aerosols from 1850 to 2010 was −1.23 W m−2, with ERFari and ERFaci of −0.23 and −1.01 W m−2, respectively. The global annual mean surface temperature and water evaporation and precipitation were reduced by 1.74 K and 0.14 mm d−1 for EM scheme and 1.28 K and 0.11 mm d−1 for PIM scheme, respectively. However, the relative humidity near the surface was slightly increased for both mixing cases. The Intertropical Convergence Zone was southwardly shifted for both EM and PIM cases but was less southwardly shifted in PIM scheme due to the less reduction in atmospheric temperature in the midlatitude and low latitude of the Northern Hemisphere.

Diurnal and day-to-day characteristics of ambient particle mass size distributions from HR-ToF-AMS measurements at an urban site and a suburban site in Hong Kong

Abstract. Mass-concentration-based particle size distributions measured by a high-resolution aerosol mass spectrometer were systematically analyzed to assess long and short-term temporal characteristics of ambient particle size distributions sampled at a typical urban environment close to emission sources and a suburban coastal site representing a regional and local pollution receptor location in Hong Kong. Measured distributions were bimodal and deconvoluted into submodes, which were analyzed for day-to-day variations and diurnal variations. Traffic and cooking emissions at the urban site contributed substantially to particle mass in both modes, while notable decreases in mass median diameters were limited to the morning rush hour. Inorganic particle components displayed varying diurnal behavior, including nocturnal nitrate formation and daytime photochemical formation evident in both modes. Suburban particle size distributions exhibited notable seasonal disparities with differing influence of local formation, particularly in spring and summer, and transport which dominated in the fall season leading to notably higher sulfate and organic accumulation-mode particle concentrations. Variations in particle mixing state were evaluated by comparison of interspecies mass median diameter trends at both measurement sites. Internal mixing was prevalent in the accumulation mode in spring at the urban site, while greater frequency of time periods with external mixing of particle populations comprising different fractions of organic constituents was observed in summer. At the suburban site, sulfate and nitrate in the accumulation mode more frequently exhibited differing particle size distributions in all seasons, signifying a greater extent of external mixing. At the urban site, periods of greater submicron inorganic mass concentrations were more likely to be caused by increases in both Aitken- and accumulation-mode particle mass in summer, while at the suburban receptor location, organic and nitrate Aitken-mode particle mass contributed more regularly to higher total submicron species mass concentrations in most seasons (spring, summer, and winter).

Anomalous low-temperature thermodynamics of QCD in strong magnetic fields

The thermodynamics of quantum chromodynamics at low temperatures and in sufficiently strong magnetic fields is governed by neutral pions. We analyze the interacting system of neutral pions and photons at zero baryon chemical potential using effective field theory. As a consequence of the axial anomaly and the external magnetic field, the pions and photons mix with one another. The resulting spectrum contains one usual, relativistic photon state, and two nonrelativistic modes, one of which is gapless and the other gapped. Furthermore, we calculate the leading, one-loop contribution to the pressure of the system. In the chiral limit, a closed analytic expression for the pressure exists, which features an unusual scaling with temperature and magnetic field, T3B/fπ, at low temperatures, T ≪ B/fπ. Finally, we determine the pion decay rate as a function of the magnetic field at the tree level. The result is affected by a competition of the anisotropic kinematics and the enlarged phase space due to the anomalous mass of the neutral pion. In the chiral limit, the decay rate scales as B3/fπ5.

Most probable mixing state of aerosols in Delhi NCR, northern India

Unknown mixing state is one of the major sources of uncertainty in estimating aerosol direct radiative forcing (DRF). Aerosol DRF in India is usually reported for external mixing and any deviation from this would lead to high bias and error. Limited information on aerosol composition hinders in resolving this issue in India. Here we use two years of aerosol chemical composition data measured at megacity Delhi to examine the most probable aerosol mixing state by comparing the simulated clear-sky downward surface flux with the measured flux. We consider external, internal, and four combinations of core-shell (black carbon, BC over dust; water-soluble, WS over dust; WS over water-insoluble, WINS and BC over WINS) mixing. Our analysis reveals that choice of external mixing (usually considered in satellite retrievals and climate models) seems reasonable in Delhi only in the pre-monsoon (Mar-Jun) season. During the winter (Dec-Feb) and monsoon (Jul-Sep) seasons, ‘WS coating over dust’ externally mixed with BC and WINS appears to be the most probable mixing state; while ‘WS coating over WINS’ externally mixed with BC and dust seems to be the most probable mixing state in the post-monsoon (Oct–Nov) season. Mean seasonal TOA (surface) aerosol DRF for the most probable mixing states are 4.4±3.9 (−25.9±3.9), −16.3±5.7 (−42.4±10.5), 13.6±11.4 (−76.6±16.6) and −5.4±7.7 (−80.0±7.2)Wm−2 respectively in the pre-monsoon, monsoon, post-monsoon and winter seasons. Our results highlight the importance of realistic mixing state treatment in estimating aerosol DRF to aid in policy making to combat climate change.

Effects of chemical composition and mixing state on size‐resolved hygroscopicity and cloud condensation nuclei activity of submicron aerosols at a suburban site in northern Japan in summer

AbstractAmbient hygroscopic properties, numbers of size‐segregated cloud condensation nuclei (CCN) at different supersaturations (0.1%–0.8%), and the chemical composition of submicron particles were simultaneously measured at a suburban site in northern Japan in summer. Two distinct periods with different growth factors (GF), CCN activation diameters, and chemical compositions were observed. The data suggest that internally mixed sulfate aerosols dominated the accumulation size mode in relatively aged aerosols during the first period, whereas particles observed during the latter periods showed external mixing dominated by organics, which was linked to low hygroscopicity and CCN activity. In particular, the higher loading of water‐soluble organic matter (WSOM; ~60% of OM by mass) with increased WSOM/sulfate ratios corresponded to a low hygroscopicity parameter derived from the CCN measurement (κCCN = 0.15 ± 0.02) at a dry diameter (Ddry) of 146 nm. The results suggest that WSOM, likely dominated by the influence of biogenic sources, contributed to reducing the hygroscopicity and CCN activation at this particle size. Temporal variations in the number concentrations for low GF mode at Ddry = 49.6 nm were similar to those in the elemental carbon (EC) concentration, suggesting that EC contributed to reducing hygroscopicity at this smaller size. Our results suggest that chemical composition and mixing state are important factors controlling the hygroscopicity and CCN activation of submicron particles. These results provide useful data sets of size‐resolved subsaturated and supersaturated hygroscopicity and highlight the importance of the abundance of OM relative to sulfate in predicting the effects on climate change.

Arthroscopic Airbrush-Assisted Cell Spraying for Cartilage Repair: Design, Development, and Characterization of Custom-Made Arthroscopic Spray Nozzles

Airbrush-assisted cell spraying would facilitate fully arthroscopic filling of cartilage defects, thereby providing a minimally invasive procedure for cartilage repair. This study provides the development and characterization of custom-made spray nozzles that could serve as a foundation for the development of a BioAirbrush, a platform technology for the arthroscopic application of (cell laden) hydrogels. Custom-made spray nozzles were designed and produced with 3D printing technology. A commercially available spraying system was used for comparison. Sprays were characterized based on spray angle, cone width, droplet size, velocity, and density. This was performed with conventional and high-speed imaging. Furthermore, cell survival of chondrocytes and mesenchymal stromal cells, as well as the chondrogenic capacity of chondrocytes after spraying were evaluated. Changing nozzle design from internal to external mixing significantly increased cell survival after spraying. Custom-made spray nozzles provide larger droplets compared to the current commercially available technology, potentially improving cell survival. Sufficient mixing of two gel components was confirmed for the custom-made nozzles. Overall, custom-made nozzles improved cell survival after spraying, without significantly affecting the chondrogenic capacity of the cells. This study provides a platform for the development of a BioAirbrush for spray-assisted cell implantations in arthroscopic cartilage repair procedures. Evaluation of the fundamental characteristics of a spray as well as a study of cell survival after spraying have further expanded the knowledge regarding cell spraying for cartilage repair. Nozzle design and air pressure characteristics are essential parameters to consider for the clinical implementation of spray-assisted cell implantations.

Solute mixing regulates heterogeneity of mineral precipitation in porous media

AbstractSynchrotron X‐ray microtomography was used to track the spatiotemporal evolution of mineral precipitation and the consequent alteration of the pore structure. Column experiments were conducted by injecting CaCl2 and NaHCO3 solutions into granular porous media either as a premixed supersaturated solution (external mixing) or as separate solutions that mixed within the specimen (internal mixing). The two mixing modes produced distinct mineral growth patterns. While internal mixing promoted transverse heterogeneity with precipitation at the mixing zone, external mixing favored relatively homogeneous precipitation along the flow direction. The impact of precipitation on pore water flow and permeability was assessed via 3‐D flow simulations, which indicated anisotropic permeability evolution for both mixing modes. Under both mixing modes, precipitation decreased the median pore size and increased the skewness of the pore size distribution. Such similar pore‐scale evolution patterns suggest that the clogging of individual pores depends primarily on local supersaturation state and pore geometry.

Evidence for marine biogenic influence on summertime Arctic aerosol

AbstractWe present vertically resolved observations of aerosol composition during pristine summertime Arctic background conditions. The methansulfonic acid (MSA)‐to‐sulfate ratio peaked near the surface (mean 0.10), indicating a contribution from ocean‐derived biogenic sulfur. Similarly, the organic aerosol (OA)‐to‐sulfate ratio increased toward the surface (mean 2.0). Both MSA‐to‐sulfate and OA‐to‐sulfate ratios were significantly correlated with FLEXPART‐WRF‐predicted air mass residence time over open water, indicating marine‐influenced OA. External mixing of sea salt aerosol from a larger number fraction of organic, sulfate, and amine‐containing particles, together with low wind speeds (median 4.7 m s−1), suggests a role for secondary organic aerosol formation. Cloud condensation nuclei concentrations were nearly constant (∼120 cm−3) when the OA fraction was <60% and increased to 350 cm−3 when the organic fraction was larger and residence times over open water were longer. Our observations illustrate the importance of marine‐influenced OA under Arctic background conditions, which are likely to change as the Arctic transitions to larger areas of open water.

Metrics to quantify the importance of mixing state for CCN activity

Abstract. It is commonly assumed that models are more prone to errors in predicted cloud condensation nuclei (CCN) concentrations when the aerosol populations are externally mixed. In this work we investigate this assumption by using the mixing state index (χ) proposed by Riemer and West (2013) to quantify the degree of external and internal mixing of aerosol populations. We combine this metric with particle-resolved model simulations to quantify error in CCN predictions when mixing state information is neglected, exploring a range of scenarios that cover different conditions of aerosol aging. We show that mixing state information does indeed become unimportant for more internally mixed populations, more precisely for populations with χ larger than 75 %. For more externally mixed populations (χ below 20 %) the relationship of χ and the error in CCN predictions is not unique and ranges from lower than −40 % to about 150 %, depending on the underlying aerosol population and the environmental supersaturation. We explain the reasons for this behavior with detailed process analyses.

Reconciling modeling with observations of radiative absorption of black carbon aerosols

AbstractThe physical treatment of internal mixing and aging of black carbon (BC) aerosols that allow for enhanced solar absorption of the BC is an important parameterization in climate models. Many climate models predict a factor of 2–3 lower aerosol absorption optical depth (AAOD) than the atmospheric columnar absorption observed from ground‐based networks such as AERONET, likely because these models do not parameterize properly the BC absorption enhancement (EMAC). Models that are configured with an internal mixing have predicted large variations of EMAC, which are poorly constrained from ambient measurements. We determined the BC EMAC from aerosol coatings with a two‐step solvent experiment to remove both organic and inorganic coatings in ambient fine particulate matter (PM2.5). Observations in a rural North China site showed that the EMAC varied from 1.4 to 3. The EMAC increases simultaneously with SO42−/EC ratios, suggesting the photochemical production of sulfate coatings enhanced BC absorption. A global climate model, parameterized to account for these observational constraints, verifies that sulfates are primary drivers of the BC absorption enhancement in severely polluted area in China. This magnification of the radiative forcing of coated BC is stronger by a factor of ~2 than predicted by the standard parameterization (external mixing) in the climate model and is in better agreement with AERONET observations of AAOD. This result would be useful for testing the representation of solar absorption by BC‐containing particles in the newer generation of climate models.

Simulated effects of internal mixing of anthropogenic aerosols on the aerosol–radiation interaction and global temperature

ABSTRACTA partial internal mixing (PIM) treatment of black carbon (BC), organic carbon (OC), and sulphate was examined, and the core‐shell model was used to represent the internally mixed aerosols with BC as the core and sulphate or OC as the shell. The influences of PIM treatment on the effective radiative forcing due to aerosol–radiative interaction (ERFari) and global temperature were examined and compared to those of external mixing (EM) treatment using an aerosol‐climate online coupled model of BCC_AGCM2.0_CUACE/Aero. Radiative forcing due to aerosol–radiation interaction (RFari) of the anthropogenic aerosols since the preindustrial era was −0.34 W m−2 for EM and −0.23 W m−2 for PIM, respectively. The global annual mean ERFari of anthropogenic aerosols since the preindustrial era was −0.42 W m−2 for EM and −0.34 W m−2 for PIM, respectively. The change in global annual mean surface temperature increased accordingly from −0.18 K in the EM case to −0.125 K in the PIM case. Well geographic consistence between the change in low‐level cloud amount and the change in temperature can be found. The atmospheric temperature in the troposphere was markedly less reduced in the PIM case than in the EM case. The RFari/ERFari for 50% and 100% were −0.11/–0.07 and 0.13/0.14 W m−2, respectively. RFari, ERFari, and surface temperature changed approximately linearly with the internal mixing proportion.

Zonal Detached Eddy Simulations of a Dual-Stream Jet: Turbulence Rate Sensitivity

This paper investigates the effect of turbulence injection using the random flow generation technique at the inlet boundaries of the core and fan channels of a dual-stream nozzle with an external plug. The objective is to reproduce the turbulence rate at the center of the nozzle ducts’ exhaust. The nozzle design and operating conditions are typically those of an aircraft engine at cruise, although the external flow is not simulated. The paper focuses on the effects of the nozzle exhaust turbulence characteristics, namely turbulent length scales and turbulent rate, on the jet flow prediction and the mixing-layer development. The results are discussed in terms of Reynolds-averaged data and spectral content. Turbulence injection over the whole height of the nozzle ducts accelerates the Reynolds-averaged Navier–Stokes to large-eddy simulation transition in both external and internal mixing layers, which is in better agreement with the experimental results. The transition length is further reduced when the injected turbulent ratio is higher but also when the injected turbulent length scale is smaller. Of interest, the shock-cell positioning in the fan jet is also improved using random flow generation, which emphasizes the importance of accounting for upstream turbulence for this type of simulation.

Experimental Investigation on the Spray Combustion Produced by an External Mixing Air Assist Atomizer

Experimental Investigation on the Spray Combustion Produced by an External Mixing Air Assist Atomizer

Experimental Investigation on the Spray Combustion Produced by an External Mixing Air Assist Atomizer

The combustion of spray of liquid fuels has a significant importance in the industry field. This paper describes an experimental study to understand and analyze the flame structure of a light diesel fuel. A special design of an external mixing air assist atomizer is used for the atomization. The atomizer installed through burner tube. Combustion tests in a small scale laboratory furnace are carried out to select the optimum operating conditions for good combustion and low emissions. The emissions (CO and NOx), combustion efficiency, axial and radial inflame temperature profiles and the heat transfer distribution for the water jacket are measured at various operating conditions. Visual observation of free jet flames was taken over wide ranges of atomizing air pressure. It is found that increasing the atomizing air pressure with the same air to fuel ratio, leads to decreasing the amount of heat flux to the cooling water jacket, decreasing in the combustion efficiency and increasing in CO and NOx emissions. It is noticed that increasing in air to fuel ratio (A/F) at the same fuel flow rate leads to decreasing in CO and NOx emissions.

Morphochemical characteristics and mixing state of long range transported wildfire particles at Ny-Ålesund (Svalbard Islands)

A prolonged and exceptionally intense air mass advection event transporting biomass burning aerosols generated in Alaska affected Ny-Ålesund in the mid of July 2015. This paper reports the morphochemical characteristics and mixing state of individual aerosol particles collected during the event. To this aim aerosol samples were collected on nucleopore polycarbonate membrane filters using a DEKATI 12-stage low volume impactor and analyzed by scanning electron microscopy (SEM) techniques. Results of SEM investigations depict a complex aerosol characterized by an external mixing between a main part of carbonaceous organic particles (tar balls and organic particles), lower ammonium sulfate and minor potassium chloride and mineral dust amounts. The carbonaceous particles are spherical to slightly elongated and the organic particles show an internal mixing of low density organics and/or ammonium sulfate upon denser nuclei. Most particles are in the accumulation mode size range although the size and the morphology of the chloride and the sulfate salts evidence the growth of these species both in the air and upon the sampling membranes. Individual particle analyses were complemented by aerosol size distribution (Aerodynamic Particle Sizer, Scanning Mobility Particle Sizer) and optical (Particle Soot Absorption Photometer, nephelometer) measurements at ground level in order to retrieve the optical and radiative properties of the aerosol in the atmosphere and to predict the fate and behaviour of particles upon deposition at ground level. Individual particle analyses were also compared with bulk chemical analyses on daily sampling filters and back-trajectory analyses of the air mass movement in order to enucleate distinct sources of the aerosol during the long range transport.

Partially Homogenous Charge Compression Ignition Engine Development for Low Volatility Fuels

Control of harmful pollutants such as oxides of nitrogen (NOx), particulate matter (PM)/ soot, carbon monoxide (CO), and hydrocarbons (HC) emitted by diesel engines is essential in order to protect the environment and human health. Different versions of low temperature combustion (LTC) concepts have shown their potential in controlling these pollutants, while achieving thermal efficiencies similar to conventional compression ignition (CI) engines. In this study, a diesel fueled partially premixed homogeneous charge compression ignition (PHCCI) engine was investigated to explore the feasibility of LTC combustion. All experiments were performed on a constant speed two cylinder engine prototype, in which one cylinder was modified to operate in PHCCI combustion mode and the other cylinder operated in conventional CI combustion mode. An external mixing device, called a “fuel vaporizer”, was developed for partially homogeneous fuel-air mixing. For a better understanding of the effect of intake charge temperatur...

Impact of mixing state and hygroscopicity on CCN activity of biomass burning aerosol in Amazonia

Abstract. Smoke aerosols prevail throughout Amazonia because of widespread biomass burning during the dry season, and external mixing, low variability in the particle size distribution and low particle hygroscopicity are typical. There can be profound effects on cloud properties. This study uses an adiabatic cloud model to simulate the activation of smoke particles as cloud condensation nuclei (CCN) for three hypothetical case studies, chosen as to resemble biomass burning aerosol observations in Amazonia. The relative importance of variability in hygroscopicity, mixing state, and activation kinetics for the activated fraction and maximum supersaturation is assessed. For a population with κp = 0.04, an overestimation of the cloud droplet number concentration Nd for the three selected case studies between 22.4 ± 1.4 and 54.3 ± 3.7 % was obtained when assuming a hygroscopicity parameter κp = 0.20. Assuming internal mixing of the aerosol population led to overestimations of up to 20 % of Nd when a group of particles with medium hygroscopicity was present in the externally mixed population cases. However, the overestimations were below 10 % for external mixtures between very low and low-hygroscopicity particles, as seems to be the case for Amazon smoke particles. Kinetic limitations were significant for medium- and high-hygroscopicity particles, and much lower for very low and low-hygroscopicity particles. When particles were assumed to be at equilibrium and to respond instantly to changes in the air parcel supersaturation, the overestimation of the droplet concentration was up to ∼ 100 % in internally mixed populations, and up to ∼ 250 % in externally mixed ones, being larger for the higher values of hygroscopicity. In addition, a perceptible delay between the times when maximum supersaturation and maximum aerosol activated fraction are reached was noticed and, for aerosol populations with effective hygroscopicity κpeff higher than a certain threshold value, the delay in particle activation was such that no particles were activated at the time of maximum supersaturation. Considering internally mixed populations, for an updraft velocity W = 0.5 m s−1 this threshold of no activation varied between κpeff = 0.35 and κpeff = 0.5 for the different case studies. However, for low hygroscopicity, kinetic limitations played a weaker role for CCN activation of particles, even when taking into account the large aerosol mass and number concentrations. For the very low range of hygroscopicities, the overestimation of the droplet concentration due to the equilibrium assumption was lowest and the delay between the times when maximum supersaturation and maximum activated fraction were reached was greatly reduced or no longer observed (depending on the case study). These findings on uncertainties and sensitivities provide guidance on appropriate simplifications that can be used for modeling of smoke aerosols within general circulation models. The use of medium values of hygroscopicity representative of smoke aerosols for other biomass burning regions on Earth can lead to significant errors compared to the use of low hygroscopicity for Amazonia (between 0.05 and 0.13, according to available observations). Also in this region, consideration of the biomass burning population as internally mixed will lead to small errors in the droplet concentration, while significantly increasing the computational burden. Regardless of the large smoke aerosol loads in the region during the dry season, kinetic limitations are expected to be low.