Article

New-particle formation events in a continental boundary layer: first results from the SATURN experiment

ATMOSPHERIC CHEMISTRY AND PHYSICS (Impact Factor: 5.3). 09/2003; DOI: 10.5194/acpd-3-1693-2003
Source: DOAJ

ABSTRACT During the SATURN experiment, which took place from 27 May to 14 June 2002, new particle formation in the continental boundary layer was investigated. Simultaneous ground-based and tethered-balloon-borne measurements were performed, including meteorological parameters, particle number concentrations and size distributions, gaseous precursor concentrations and SODAR and LIDAR observations.

Newly formed particles were observed inside the residual layer, before the break-up process of the nocturnal inversion, and inside the mixing layer throughout the break-up of the nocturnal inversion and during the evolution of the planetary boundary layer.

Download full-text

Full-text

Available from: Ulrich Uhrner, Aug 01, 2015
1 Follower
 · 
121 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aerosol particles in the atmosphere are known to significantly influence ecosystems, to change air quality and to exert negative health effects. Atmospheric aerosols influence climate through cooling of the atmosphere and the underlying surface by scattering of sunlight, through warming of the atmosphere by absorbing sun light and thermal radiation emitted by the Earth surface and through their acting as cloud condensation nuclei. Aerosols are emitted from both natural and anthropogenic sources. Depending on their size, they can be transported over significant distances, while undergoing considerable changes in their composition and physical properties. Their lifetime in the atmosphere varies from a few hours to a week. New particle formation is a result of gas-to-particle conversion. Once formed, atmospheric aerosol particles may grow due to condensation or coagulation, or be removed by deposition processes. In this thesis we describe analyses of air masses, meteorological parameters and synoptic situations to reveal conditions favourable for new particle formation in the atmosphere. We studied the concentration of ultrafine particles in different types of air masses, and the role of atmospheric fronts and cloudiness in the formation of atmospheric aerosol particles. The dominant role of Arctic and Polar air masses causing new particle formation was clearly observed at Hyytiälä, Southern Finland, during all seasons, as well as at other measurement stations in Scandinavia. In all seasons and on multi-year average, Arctic and North Atlantic areas were the sources of nucleation mode particles. In contrast, concentrations of accumulation mode particles and condensation sink values in Hyytiälä were highest in continental air masses, arriving at Hyytiälä from Eastern Europe and Central Russia. The most favourable situation for new particle formation during all seasons was cold air advection after cold-front passages. Such a period could last a few days until the next front reached Hyytiälä. The frequency of aerosol particle formation relates to the frequency of low-cloud-amount days in Hyytiälä. Cloudiness of less than 5 octas is one of the factors favouring new particle formation. Cloudiness above 4 octas appears to be an important factor that prevents particle growth, due to the decrease of solar radiation, which is one of the important meteorological parameters in atmospheric particle formation and growth. Keywords: Atmospheric aerosols, particle formation, air mass, atmospheric front, cloudiness Aerosol particles in the atmosphere are known to significantly influence ecosystems, to change air quality and to exert negative health effects. Atmospheric aerosols influence climate through cooling of the atmosphere and the underlying surface by scattering of sunlight, through warming of the atmosphere by absorbing sun light and thermal radiation emitted by the Earth surface and through their acting as cloud condensation nuclei. Aerosols are emitted from both natural and anthropogenic sources. Depending on their size, they can be transported over significant distances, while undergoing considerable changes in their composition and physical properties. Their lifetime in the atmosphere varies from a few hours to a week. New particle formation is a result of gas-to-particle conversion. Once formed, atmospheric aerosol particles may grow due to condensation or coagulation, or be removed by deposition processes. In this thesis we describe analyses of air masses, meteorological parameters and synoptic situations to reveal conditions favourable for new particle formation in the atmosphere. We studied the concentration of ultrafine particles in different types of air masses, and the role of atmospheric fronts and cloudiness in the formation of atmospheric aerosol particles. The dominant role of Arctic and Polar air masses causing new particle formation was clearly observed at Hyytiälä, Southern Finland, during all seasons, as well as at other measurement stations in Scandinavia. In all seasons and on multi-year average, Arctic and North Atlantic areas were the sources of nucleation mode particles. In contrast, concentrations of accumulation mode particles and condensation sink values in Hyytiälä were highest in continental air masses, arriving at Hyytiälä from Eastern Europe and Central Russia. The most favourable situation for new particle formation during all seasons was cold air advection after cold-front passages. Such a period could last a few days until the next front reached Hyytiälä. The frequency of aerosol particle formation relates to the frequency of low-cloud-amount days in Hyytiälä. Cloudiness of less than 5 octas is one of the factors favouring new particle formation. Cloudiness above 4 octas appears to be an important factor that prevents particle growth, due to the decrease of solar radiation, which is one of the important meteorological parameters in atmospheric particle formation and growth. Keywords: Atmospheric aerosols, particle formation, air mass, atmospheric front, cloudiness
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Atmospheric aerosol particles affect the global climate as well as human health. In this thesis, formation of nanometer sized atmospheric aerosol particles and their subsequent growth was observed to occur all around the world. Typical formation rate of 3 nm particles at varied from 0.01 to 10 cm-3s-1. One order of magnitude higher formation rates were detected in urban environment. Highest formation rates up to 105 cm-3s-1 were detected in coastal areas and in industrial pollution plumes. Subsequent growth rates varied from 0.01 to 20 nm h-1. Smallest growth rates were observed in polar areas and the largest in the polluted urban environment. This was probably due to competition between growth by condensation and loss by coagulation. Observed growth rates were used in the calculation of a proxy condensable vapour concentration and its source rate in vastly different environments from pristine Antarctica to polluted India. Estimated concentrations varied only 2 orders of magnitude, but the source rates for the vapours varied up to 4 orders of magnitude. Highest source rates were in New Delhi and lowest were in the Antarctica. Indirect methods were applied to study the growth of freshly formed particles in the atmosphere. Also a newly developed Water Condensation Particle Counter, TSI 3785, was found to be a potential candidate to detect water solubility and thus indirectly composition of atmospheric ultra-fine particles. Based on indirect methods, the relative roles of sulphuric acid, non-volatile material and coagulation were investigated in rural Melpitz, Germany. Condensation of non-volatile material explained 20-40% and sulphuric acid the most of the remaining growth up to a point, when nucleation mode reached 10 to 20 nm in diameter. Coagulation contributed typically less than 5%. Furthermore, hygroscopicity measurements were applied to detect the contribution of water soluble and insoluble components in Athens. During more polluted days, the water soluble components contributed more to the growth. During less anthropogenic influence, non-soluble compounds explained a larger fraction of the growth. In addition, long range transport to a measurement station in Finland in a relatively polluted air mass was found to affect the hygroscopicity of the particles. This aging could have implications to cloud formation far away from the pollution sources. Hengittämässämme ilmassa on koko ajan pieniä kiinteitä tai nestemäisiä aerosolihiukkasia, jotka ovat liian pieniä pudotakseen maahan maan vetovoiman vaikutuksesta. Esimerkiksi pölyhitunen on aerosolihiukkanen. Yleisesti aerosolihiukkaset esimerkiksi heikentävät näkyvyyttä ja aiheuttavat hengityselin- ja sydänsairauksia. Lisäksi ne vaikuttavat koko maapallon ilmastoon, koska pilvet muodostuvat aerosolihiukkasten päälle. Ilmakehään aerosolihiukkaset joutuvat esimerkiksi tuulen nostaessa ilmaan aavikon hiekkaa, meren pärskeistä tai erilaisten kaasujen tiivistyessä. Väitöskirjassani tutkin hyvin pienten (halkaisijaltaan alle 100 nm, 1 nanometri on miljoonasosa millimetristä) aerosolihiukkasten muodostumista, kasvua ja ominaisuuksia. Väitöskirjassa kokosin yhteen viimeisten vuosikymmenien aikana tehdyt havainnot eri puolilta maapalloa. Yli sadassa tutkimuksessa havaittiin, että uusia aerosolihiukkasia muodostuu ilmakehässä kaikkialla: esimerkiksi Lapissa, Keski-Euroopassa, saastuneessa New Delhissä ja Antarktiksella. Tarkkaa muodostumismekanismia ei vielä tiedetä. Kaasuista muodostuneet hiukkaset ovat kooltaan niin pieniä, että niiden kemiallista koostumusta on hyvin vaikea mitata. Tässä työssä tarkkailtiin uusien, juuri muodostuneitten hiukkasten ominaisuuksien muutoksia, joka kertoi hiukkasten kemiallisen koostumuksen muutoksista. Mittaukset tehtiin Suomessa, Saksassa, Kreikassa ja Ranskassa. Saastuneessa ilmassa muodostuneitten uusien hiukkasten ominaisuudet poikkesivat puhtaassa ilmassa muodostuneista hiukkasista. Tämä voi puolestaan vaikuttaa esimerkiksi pilvien muodostumiseen ja sateen alueelliseen jakautumiseen.
Show more