Ion-induced aerosol formation in a H2O-H2SO4 system—II. Numerical calculations and conclusions

“…The time evolution of the particle number concentration in section i is given by [Raes and Janssens, 1986] strong decrease while crossing the tropopause. This decrease is observed between 200 and 300 ppbv ozone.…”

Section: Model Descriptionmentioning

confidence: 99%

Airborne aerosol measurements in the tropopause region and the dependence of new particle formation on preexisting particle number concentration

Reus¹,

Ström²,

Kulmala³

et al. 1998

J. Geophys. Res.

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Abstract. Airborne measurements of aerosol particles and trace gases were performed at midlatitudes in the Stratosphere-Troposphere Experiment by Aircraft Measurements (STREAM-96) campaign during late spring in the free troposphere and lower stratosphere. The results show a consistent relation between particle number concentration and water vapor mixing ratio, suggesting a minimum particle number concentration below which nucleation of particles is very likely to occur. Numerical simulations, using a coupled atmospheric chemistry and aerosol nucleation model, support this hypothesis. The model calculations indicate that new particle formation is very sensitive to the preexisting particle number concentration in the tropopause region. To be able to quantify and predict future aerosol effects regarding climate, chemistry, and human health, it is essential to improve our understanding about how particles form, transform, and are removed from the atmosphere. Of these three processes, particle formation is perhaps the least understood.Numerous events of particle formation have been reported, most frequently from observations in the marine boundary The most important mechanism for new particle production ;o thought to be binary homogeneous nucleation of sulphuric acid and water vapor. At a certain critical supersaturation of sulphuric acid the vapor condenses and forms new particles. At increasing relative humidity this threshold is significantly reduced, and particle formation can occur at much lower H2SO 4 concentrations [Kulmala et al., 1995]. Normally, the concentration of n2so 4 vapor in the atmosphere is controlled by the balance between the source, that is, oxidation of SO2 by OH, and the sink, condensation on preexisting particles. The available aerosol surface area and number concentration determines the rate of condensation [Pirjola and Kulmala, 1998]. Thus a low preexisting particle number concentration and surface area, high humidity, and high precursor gas concentrations (OH and SO2) favor this type of particle formation. Observations by Brock et al. [1995] showed that particles in the upper tropical troposphere were composed of H2SO4-H20 droplets and thus were very likely formed by homogeneous nucleation of sulphuric acid and water vapor. Covert et al.[1992] reported events of new particle formation in the marine boundary layer connected to periods with low aerosol surface area at times when there was no SO2 enhancement. An inverse relationship between surface area and ultrafine particles was also observed by Clarke [1992] in the upper troposphere. Hegg et al. [1990] found new particle production just above the cloud top in the marine boundary layer, presumably due to increased relative humidity caused by the evaporation of cloud droplets. Cases of new particle formation in the marine boundary layer by oxidation of SO2 and subsequent condensation of H2SO 4 have been shown by Hoppel et al. [1994]. However, the sulphuric acid concentrations were probably well below the binary 31,255

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“…Multimodal moment models (Kulmala et al, 1995;Whitby and McMurry, 1997;Wilck and Stratmann, 1997;Pirjola and Kulmala, 1998;Wilck, 1998); 3. Sectional models (Raes and Janssens, 1986;Kerminen and Wexler, 1997;Pirjola, 1999;Korhonen et al, 2004;Gaydos et al, 2005).…”

mentioning

confidence: 99%

Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part I: Modelling approach

Hellmuth

2006

Atmos. Chem. Phys.

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Abstract.A high-order modelling approach to interpret "continental-type" particle formation bursts in the anthropogenically influenced convective boundary layer (CBL) is proposed. The model considers third-order closure for planetary boundary layer turbulence, sulphur and ammonia chemistry as well as aerosol dynamics. In Paper I of four papers, previous observations of ultrafine particle evolution are reviewed, model equations are derived, the model setup for a conceptual study on binary and ternary homogeneous nucleation is defined and shortcomings of process parameterisation are discussed. In the subsequent Papers II, III and IV simulation results, obtained within the framework of a conceptual study on the CBL evolution and new particle formation (NPF), will be presented and compared with observational findings.

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Ion-induced aerosol formation in a H2O-H2SO4 system—II. Numerical calculations and conclusions

Cited by 49 publications

References 6 publications

On the photochemical production of new particles in the coastal boundary layer

On the photochemical production of new particles in the coastal boundary layer

Airborne aerosol measurements in the tropopause region and the dependence of new particle formation on preexisting particle number concentration

Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part I: Modelling approach

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