scholarly journals No statistically significant effect of a short-term decrease in the nucleation rate on atmospheric aerosols

2012 ◽  
Vol 12 (23) ◽  
pp. 11573-11587 ◽  
Author(s):  
E. M. Dunne ◽  
L. A. Lee ◽  
C. L. Reddington ◽  
K. S. Carslaw
Keyword(s):  
Nucleation Rate ◽  
Atmospheric Aerosols ◽  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
Cosmic Ray ◽  
Condensation Nucleus ◽  
Cloud Condensation Nucleus ◽  
Significant Response ◽  
Short Term ◽  
Aerosol Properties

Abstract. Observed correlations between short-term decreases in cosmic ray ionisation and cloud and aerosol properties have been attributed to short-term decreases in the ion-induced nucleation rate. We use a global aerosol microphysics model to determine whether a 10 day reduction of 15% in the nucleation rate could generate a statistically significant response in aerosol concentrations and optical properties. As an upper limit to the possible effect of changes in ion-induced nucleation rate, we perturb the total nucleation rate, which has been shown to generate particle concentrations and nucleation events in reasonable agreement with global observations. When measured against a known aerosol control state, the model predicts a 0.15% decrease in global mean cloud condensation nucleus concentration at the surface. However, taking into account the variability in aerosol, no statistically significant response can be detected in concentrations of particles with diameters larger than 10 nm, in cloud condensation nuclei with diameters larger than 70 nm, or in the Ångström exponent. The results suggest that the observed correlation between short-term decreases in cosmic ray ionisation and cloud and aerosol properties cannot be explained by associated changes in the large-scale nucleation rate.

scholarly journals No statistically significant effect of a short-term decrease in the nucleation rate on atmospheric aerosols

2012 ◽  
Vol 12 (6) ◽  
pp. 15373-15417 ◽  
Author(s):  
E. M. Dunne ◽  
L. A. Lee ◽  
C. L. Reddington ◽  
K. S. Carslaw
Keyword(s):  
Nucleation Rate ◽  
Atmospheric Aerosols ◽  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
Cosmic Ray ◽  
Condensation Nucleus ◽  
Cloud Condensation Nucleus ◽  
Significant Response ◽  
Short Term ◽  
Aerosol Properties

Abstract. Observed correlations between short-term decreases in cosmic ray ionisation and cloud and aerosol properties have been attributed to short-term decreases in the ion-induced nucleation rate. We use a global aerosol microphysics model to determine whether a 10-day reduction of 15% in the nucleation rate could generate a statistically significant response in aerosol concentrations and optical properties. As an upper limit to the possible effect of changes in the ion-induced nucleation rate, we perturb the total nucleation rate, which has been shown to generate particle concentrations and nucleation events in reasonable agreement with global observations. When measured against a known aerosol control state, the model predicts a 0.15% decrease in global mean cloud condensation nucleus concentrations at the surface. However, taking into account the variability in aerosol, no statistically significant response can be detected in concentrations of particles with diameters larger than 10 nm, in cloud condensation nuclei with diameters larger than 70 nm, or in the Ångström exponent. The results suggest that the observed correlation between short-term decreases in cosmic ray ionisation and cloud and aerosol properties cannot be explained by associated changes in the large-scale nucleation rate.

scholarly journals Relating particle hygroscopicity and CCN activity to chemical composition during the HCCT-2010 field campaign

2013 ◽  
Vol 13 (16) ◽  
pp. 7983-7996 ◽  
Author(s):  
Z. J. Wu ◽  
L. Poulain ◽  
S. Henning ◽  
K. Dieckmann ◽  
W. Birmili ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Condensation Nucleus ◽  
Sampling Period ◽  
Cloud Condensation Nucleus ◽  
Mountain Range ◽  
Mixing Rule ◽  
Hygroscopic Growth ◽  
Parameter Values ◽  
Ccn Activity

Abstract. Particle hygroscopic growth at 90% RH (relative humidity), cloud condensation nuclei (CCN) activity, and size-resolved chemical composition were concurrently measured in the Thüringer Wald mid-level mountain range in central Germany in the fall of 2010. The median hygroscopicity parameter values, κ, of 50, 75, 100, 150, 200, and 250 nm particles derived from hygroscopicity measurements are respectively 0.14, 0.14, 0.17, 0.21, 0.24, and 0.28 during the sampling period. The closure between HTDMA (Hygroscopicity Tandem Differential Mobility Analyzers)-measured (κHTDMA) and chemical composition-derived (κchem) hygroscopicity parameters was performed based on the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Using size-averaged chemical composition, the κ values are substantially overpredicted (30 and 40% for 150 and 100 nm particles). Introducing size-resolved chemical composition substantially improved closure. We found that the evaporation of NH4NO3, which may happen in a HTDMA system, could lead to a discrepancy in predicted and measured particle hygroscopic growth. The hygroscopic parameter of the organic fraction, κorg, is positively correlated with the O : C ratio (κorg = 0.19 × (O : C) − 0.03). Such correlation is helpful to define the κorg value in the closure study. κ derived from CCN measurement was around 30% (varied with particle diameters) higher than that determined from particle hygroscopic growth measurements (here, hydrophilic mode is considered only). This difference might be explained by the surface tension effects, solution non-ideality, gas-particle partitioning of semivolatile compounds, and the partial solubility of constituents or non-dissolved particle matter. Therefore, extrapolating from HTDMA data to properties at the point of activation should be done with great care. Finally, closure study between CCNc (cloud condensation nucleus counter)-measured (κCCN) and chemical composition (κCCN, chem) was performed using CCNc-derived κ values for individual components. The results show that the κCCN can be well predicted using particle size-resolved chemical composition and the ZSR mixing rule.

scholarly journals A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties

2005 ◽  
Vol 5 (12) ◽  
pp. 3233-3250 ◽  
Author(s):  
D. V. Spracklen ◽  
K. J. Pringle ◽  
K. S. Carslaw ◽  
M. P. Chipperfield ◽  
G. W. Mann
Keyword(s):  
Nucleation Rate ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Accommodation Coefficient ◽  
Sulfate Aerosol ◽  
Sea Salt ◽  
Condensation Nuclei ◽  
Microphysical Processes ◽  
Global Mean ◽  
Aerosol Properties

Abstract. We use the new GLOMAP model of global aerosol microphysics to investigate the sensitivity of modelled sulfate and sea salt aerosol properties to uncertainties in the driving microphysical processes and compare these uncertainties with those associated with aerosol and precursor gas emissions. Overall, we conclude that uncertainties in microphysical processes have a larger effect on global sulfate and sea salt derived condensation nuclei (CN) and cloud condensation nuclei (CCN) concentrations than uncertainties in present-day sulfur emissions. Our simulations suggest that uncertainties in predicted sulfate and sea salt CCN abundances due to poorly constrained microphysical processes are likely to be of a similar magnitude to long-term changes in sulfate and sea salt CCN due to changes in anthropogenic emissions. A microphysical treatment of the global sulfate aerosol allows the uncertainty in climate-relevant aerosol properties to be attributed to specific processes in a way that has not been possible with simpler aerosol schemes. In particular we conclude that: (1) changes in the binary H2SO4-H2O nucleation rate and condensation rate of gaseous H2SO4 cause a shift in the vertical location of the upper tropospheric CN layer by as much as 3 km, while the shape of the CN profile is essentially pre-served (2) uncertainties in the binary H2SO4-H2O nucleation rate have a relatively insignificant effect on marine boundary layer (MBL) aerosol properties; (3) emitting a fraction of anthropogenic SO2 as particulates (to represent production of sulfate particles in power plant plumes below the scale of the model grid (which is of the order of 300 km)) has the potential to change the global mean MBL sulfate-derived CN concentrations by up to 72%, and changes of up to a factor 20 can occur in polluted continental regions; (4) predicted global mean MBL sulfate and sea salt CCN concentrations change by 10 to 60% when several microphysical processes are changed within reasonable uncertainty ranges; (5) sulfate and sea salt derived CCN concentrations are particularly sensitive to primary particle emissions, with global mean MBL sulfate and sea salt CCN changing by up to 27% and local concentrations over continental regions changing by more than 100% when the percentage of anthropogenic SO2 emitted as particulates is changed from 0 to 5%; (6) large changes in sea spray flux have insignificant effects on global sulfate aerosol except when the mass accommodation coefficient of sulfuric acid on the salt particles is set unrealistically low.

scholarly journals The Theory of Ice Nucleation by Heterogeneous Freezing of Deliquescent Mixed CCN. Part I: Critical Radius, Energy, and Nucleation Rate

2004 ◽  
Vol 61 (22) ◽  
pp. 2676-2691 ◽  
Author(s):  
Vitaly I. Khvorostyanov ◽  
Judith A. Curry
Keyword(s):  
Nucleation Rate ◽  
Large Scale ◽  
Critical Radius ◽  
Freezing Point ◽  
Cloud Condensation Nuclei ◽  
Companion Paper ◽  
Ice Nucleation ◽  
Critical Temperatures ◽  
New Formulation ◽  
Suitable Framework

Abstract This paper extends previous work on the theory of heterogenous ice nucleation. The goals of this analysis are to explain empirical observations of ice nucleation and to provide a suitable framework for modeling and parameterizing the ice nucleation process in cloud-scale and large-scale atmospheric models. Considered are the processes of heterogeneous freezing of deliquescent mixed cloud condensation nuclei that may serve as ice nuclei, and the properties of an ice germ critical radius, energy, and nucleation rate of ice crystals are examined as functions of temperature and supersaturation. Expressions for nucleation in a polydisperse aerosol for the deliquescence-freezing mode are developed. Equations are derived for the threshold and critical saturation ratios as functions of temperature and nucleation rate, and for the threshold and critical temperatures as functions of saturation ratio. Equivalence of the new formulation for the freezing point depression with traditional expressions is shown and the concepts of the effective temperature and supercooling are introduced. These new formulations are used in a companion paper for simulations of ice nucleation using a cloud parcel model.

scholarly journals Laboratory-generated primary marine aerosol via bubble-bursting and atomization

2009 ◽  
Vol 2 (5) ◽  
pp. 2281-2320 ◽  
Author(s):  
E. Fuentes ◽  
H. Coe ◽  
D. Green ◽  
G. McFiggans
Keyword(s):  
Growth Factor ◽  
Particle Production ◽  
Condensation Nucleus ◽  
Water Jet ◽  
Cloud Condensation Nucleus ◽  
Bubble Bursting ◽  
Aerosol Generator ◽  
Critical Supersaturation ◽  
Plunging Water Jet ◽  
Aerosol Properties

Abstract. A range of bubble and sea spray aerosol generators has been tested in the laboratory and compared with ocean measurements. We have shown that the method of generation has a significant influence on the properties of the aerosol particles produced. Hence, the validity of a generation system to mimic atmospheric aerosol is dependent on its capacity of generating bubbles and particulate in a realistic manner. A bubble-bursting aerosol generator consisting in the production of bubbles by the impingement of water jets on seawater was shown to best reproduce the real oceanic bubble and aerosol distributions signatures. Two aeration methods and a plunging-water jet system were tested as bubble-bursting aerosol generators for comparison with a standard nebulizer. The methods for aerosol production were evaluated by analysing the bubble spectrum generated by the bubble-bursting systems and the submicron size distribution, hygroscopicity and cloud condensation nucleus activity of the aerosols generated by the different techniques. Significant differences in the bubble spectrum and aerosol properties were observed when using different aerosol generators. The hygroscopicity and cloud condensation nucleus activity of aerosols generated by the different methods were similar when a sample of purely inorganic salts was used as a parent seawater solution; however, significant differences in the aerosol properties were found when biogenic organics were incorporated in the seawater samples. The presence of organics in the aerosol caused suppression of the growth factor at humidities above 75% RH and an increase in the critical supersaturation when compared with the case without organics. Unequal extent of these effects was observed for aerosols generated by the different methods of particle production. While the highest reductions of the growth factor were observed for the plunging-water jet aerosol, the largest effect on the critical supersaturation was obtained for the atomization-generated particles. The results of this work show that the aerosol generation mechanism affects the particles organic enrichment, thus the behaviour of the produced aerosols strongly depends on the laboratory aerosol generator employed.

scholarly journals Dust mass, cloud condensation nuclei, and ice-nucleating particle profiling with polarization lidar: updated POLIPHON conversion factors from global AERONET analysis

2019 ◽  
Vol 12 (9) ◽  
pp. 4849-4865 ◽  
Author(s):  
Albert Ansmann ◽  
Rodanthi-Elisavet Mamouri ◽  
Julian Hofer ◽  
Holger Baars ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Surface Area ◽  
Cloud Condensation Nuclei ◽  
Condensation Nucleus ◽  
Cloud Condensation Nucleus ◽  
Conversion Factors ◽  
Microphysical Properties ◽  
Central Asian ◽  
Volume Forms ◽  
Aerosol Type

Abstract. The POLIPHON (Polarization Lidar Photometer Networking) method permits the retrieval of particle number, surface area, and volume concentration for dust and non-dust aerosol components. The obtained microphysical properties are used to estimate height profiles of particle mass, cloud condensation nucleus (CCN) and ice-nucleating particle (INP) concentrations. The conversion of aerosol-type-dependent particle extinction coefficients, derived from polarization lidar observations, into the aerosol microphysical properties (number, surface area, volume) forms the central part of the POLIPHON computations. The conversion parameters are determined from Aerosol Robotic Network (AERONET) aerosol climatologies of optical and microphysical properties. In this article, we focus on the dust-related POLIPHON retrieval products and present an extended set of dust conversion factors considering all relevant deserts around the globe. We apply the new conversion factor set to a dust measurement with polarization lidar in Dushanbe, Tajikistan, in central Asia. Strong aerosol layering was observed with mineral dust advected from Kazakhstan (0–2 km height), Iran (2–5 km), the Arabian peninsula (5–7 km), and the Sahara (8–10 km). POLIPHON results obtained with different sets of conversion parameters were contrasted in this central Asian case study and permitted an estimation of the conversion uncertainties.

scholarly journals Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

2011 ◽  
Vol 11 (8) ◽  
pp. 4001-4013 ◽  
Author(s):  
E. J. Snow-Kropla ◽  
J. R. Pierce ◽  
D. M. Westervelt ◽  
W. Trivitayanurak
Keyword(s):  
Cosmic Rays ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cloud Condensation Nuclei ◽  
Cosmic Ray ◽  
Organic Aerosol ◽  
Test Cases ◽  
Primary Emissions ◽  
Cosmic Ray Flux ◽  
Aerosol Properties

Abstract. The flux of cosmic rays to the atmosphere has been reported to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN) concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA) condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux) and solar maximum (low cosmic ray flux) simulations is less than 0.2 %. The change in the total number of particles larger than 10 nm was larger, but always less than 1 %. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

scholarly journals A single parameter representation of hygroscopic growth and cloud condensation nucleus activity

2007 ◽  
Vol 7 (8) ◽  
pp. 1961-1971 ◽  
Author(s):  
M. D. Petters ◽  
S. M. Kreidenweis
Keyword(s):  
Compositional Data ◽  
Cloud Condensation Nuclei ◽  
Condensation Nucleus ◽  
Atmospheric Particulate Matter ◽  
Cloud Condensation Nucleus ◽  
Hygroscopic Growth ◽  
Activation Data ◽  
Surface Active ◽  
Surface Active Compounds ◽  
Ccn Activity

Abstract. We present a method to describe the relationship between particle dry diameter and cloud condensation nuclei (CCN) activity using a single hygroscopicity parameter κ. Values of the hygroscopicity parameter are between 0.5 and 1.4 for highly-CCN-active salts such as sodium chloride, between 0.01 and 0.5 for slightly to very hygroscopic organic species, and 0 for nonhygroscopic components. Observations indicate that atmospheric particulate matter is typically characterized by 0.1<κ<0.9. If compositional data are available and if the hygroscopicity parameter of each component is known, a multicomponent hygroscopicity parameter can be computed by weighting component hygroscopicity parameters by their volume fractions in the mixture. In the absence of information on chemical composition, experimental data for complex, multicomponent particles can be fitted to obtain the hygroscopicity parameter. The hygroscopicity parameter can thus also be used to conveniently model the CCN activity of atmospheric particles, including those containing insoluble components. We confirm the applicability of the hygroscopicity parameter and its mixing rule by applying it to published hygroscopic diameter growth factor and CCN-activation data for single- and multi-component particles containing varying amounts of inorganic, organic and surface active compounds. We suggest that κ may be fit to CCN data assuming σs/a=0.072 J m−2 and present a table of κ derived for this value and T=298.15 K. The predicted hygroscopicities for mixtures that contain the surfactant fulvic acid agree within uncertainties with the measured values. It thus appears that this approach is adequate for predicting CCN activity of mixed particles containing surface active materials, but the generality of this assumption requires further verification.

scholarly journals Tropospheric and stratospheric wildfire smoke profiling with lidar: Mass, surface area, CCN and INP retrieval

2020 ◽  
Author(s):  
Albert Ansmann ◽  
Kevin Ohneiser ◽  
Rodanthi-Elisavet Mamouri ◽  
Daniel A. Knopf ◽  
Igor Veselovskii ◽  
...  
Keyword(s):  
Surface Area ◽  
Large Scale ◽  
Condensation Nucleus ◽  
Cloud Condensation Nucleus ◽  
Wildfire Smoke ◽  
Microphysical Properties ◽  
Southeastern Australia ◽  
Analysis Scheme ◽  
Air Chemistry ◽  
Ground Based Lidar

Abstract. We present retrievals of tropospheric and stratospheric height profiles of particle mass, volume, and surface area concentrations in the case of wildfire smoke layers as well as estimates of smoke-related cloud condensation nucleus (CCN) and ice-nucleating particle (INP) concentrations from single-wavelength backscatter lidar measurements at ground and in space. A central role in the data analysis play conversion factors to convert the measured optical into microphysical properties. The set of needed conversion parameters for wildfire smoke are derived from AERONET observations of major smoke events caused by record-breaking wildfires in western Canada in August 2017 and southeastern Australia in January–February 2020. The new smoke analysis scheme is applied to stratospheric CALIPSO observations of fresh smoke plumes over northern Canada in 2017 and New Zealand in January 2020 and to ground-based lidar observation in southern Chile in aged Australian smoke layers in January 2020. These case studies show the potential of spaceborne and ground-based lidars to document large-scale and long-lasting wildfire smoke events in large detail and thus to provide valuable information for climate-, cloud-, and air chemistry modeling efforts performed to investigate the role of wildfire smoke in the atmospheric system.

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