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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: J. Lampilahti; H. E. Manninen; T. Nieminen; S. Mirme; +29 Authors

    We compared observations of aerosol particle formation and growth in different parts of the planetary boundary layer at two different environments that have frequent new particle formation (NPF) events. In summer 2012 we had a campaign in Po Valley, Italy (urban background), and in spring 2013 a similar campaign took place in Hyytiälä, Finland (rural background). Our study consists of three case studies of airborne and ground-based measurements of ion and particle size distribution from ∼1 nm. The airborne measurements were performed using a Zeppelin inside the boundary layer up to 1000 m altitude. Our observations show the onset of regional NPF and the subsequent growth of the aerosol particles happening almost uniformly inside the mixed layer (ML) in both locations. However, in Hyytiälä we noticed local enhancement in the intensity of NPF caused by mesoscale boundary layer (BL) dynamics. Additionally, our observations indicate that in Hyytiälä NPF was probably also taking place above the ML. In Po Valley we observed NPF that was limited to a specific air mass.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Atmospheric Chemistr...arrow_drop_down
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    Authors: Lampilahti, Janne; Manninen, Hanna Elina; Leino, Katri; Väänänen, Riikka; +12 Authors

    Recent studies have shown the importance of new particle formation (NPF) to global cloud condensation nuclei (CCN) production, as well as to air pollution in megacities. In addition to the necessary presence of low-volatility vapors that can form new aerosol particles, both numerical and observational studies have shown that the dynamics of the planetary boundary layer (BL) plays an important role in NPF. Evidence from field observations suggests that roll vortices might be favorable for inducing NPF in a convective BL. However, direct observations and estimates of the potential importance of this phenomenon to the production of new aerosol particles are lacking. Here we show that rolls frequently induce NPF bursts along the horizontal circulations and that the small clusters and particles originating from these localized bursts grow in size similar to particles typically ascribed to atmospheric NPF that occur almost homogeneously at a regional scale. We outline a method to identify roll-induced NPF from measurements and, based on the collected data, estimate the impact of roll vortices on the overall aerosol particle production due to NPF at a boreal forest site (83 % ± 34 % and 26 % ± 8 % overall enhancement in particle formation for 3 and 10 nm particles, respectively). We conclude that the formation of roll vortices should be taken into account when estimating particle number budgets in the atmospheric BL.

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    Authors: Räisänen, Petri; Makkonen, Risto; Kirkevåg, Alf; Debernard, Jens B.;

    Snow consists of non-spherical grains of various shapes and sizes. Still, in radiative transfer calculations, snow grains are often treated as spherical. This also applies to the computation of snow albedo in the Snow, Ice, and Aerosol Radiation (SNICAR) model and in the Los Alamos sea ice model, version 4 (CICE4), both of which are employed in the Community Earth System Model and in the Norwegian Earth System Model (NorESM). In this study, we evaluate the effect of snow grain shape on climate simulated by NorESM in a slab ocean configuration of the model. An experiment with spherical snow grains (SPH) is compared with another (NONSPH) in which the snow shortwave single-scattering properties are based on a combination of three non-spherical snow grain shapes optimized using measurements of angular scattering by blowing snow. The key difference between these treatments is that the asymmetry parameter is smaller in the non-spherical case (0.77–0.78 in the visible region) than in the spherical case ( ≈ 0.89). Therefore, for the same effective snow grain size (or equivalently, the same specific projected area), the snow broadband albedo is higher when assuming non-spherical rather than spherical snow grains, typically by 0.02–0.03. Considering the spherical case as the baseline, this results in an instantaneous negative change in net shortwave radiation with a global-mean top-of-the-model value of ca. −0.22 W m−2. Although this global-mean radiative effect is rather modest, the impacts on the climate simulated by NorESM are substantial. The global annual-mean 2 m air temperature in NONSPH is 1.17 K lower than in SPH, with substantially larger differences at high latitudes. The climatic response is amplified by strong snow and sea ice feedbacks. It is further demonstrated that the effect of snow grain shape could be largely offset by adjusting the snow grain size. When assuming non-spherical snow grains with the parameterized grain size increased by ca. 70 %, the climatic differences to the SPH experiment become very small. Finally, the impact of assumed snow grain shape on the radiative effects of absorbing aerosols in snow is discussed.

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    Authors: M. Sipilä; T. Jokinen; T. Berndt; S. Richters; +16 Authors

    Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of the reaction of stabilized Criegee intermediates (sCIs) with SO2, atmospheric oxidation processes were thought to be dominated by a few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulfuric acid (H2SO4). The measured total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) /k(sCI + SO2), was determined at relative humidities of 10 and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0–2.4) × 1012 molecules cm−3 and nearly independent of the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster with the organic acids than with SO2; k(sCI + acid) / k(sCI + SO2) = (2.8 ± 0.3) for formic acid, and k(sCI + acid) / k(sCI + SO2) = (3.4 ± 0.2) for acetic acid. This finding indicates that sCIs can play a role in the formation and loss of other atmospheric constituents besides SO2.

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    https://doi.org/10.34657/1227...
    Article . 2014
    License: CC BY
    Data sources: Datacite
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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: J. Lampilahti; H. E. Manninen; T. Nieminen; S. Mirme; +29 Authors

    We compared observations of aerosol particle formation and growth in different parts of the planetary boundary layer at two different environments that have frequent new particle formation (NPF) events. In summer 2012 we had a campaign in Po Valley, Italy (urban background), and in spring 2013 a similar campaign took place in Hyytiälä, Finland (rural background). Our study consists of three case studies of airborne and ground-based measurements of ion and particle size distribution from ∼1 nm. The airborne measurements were performed using a Zeppelin inside the boundary layer up to 1000 m altitude. Our observations show the onset of regional NPF and the subsequent growth of the aerosol particles happening almost uniformly inside the mixed layer (ML) in both locations. However, in Hyytiälä we noticed local enhancement in the intensity of NPF caused by mesoscale boundary layer (BL) dynamics. Additionally, our observations indicate that in Hyytiälä NPF was probably also taking place above the ML. In Po Valley we observed NPF that was limited to a specific air mass.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Atmospheric Chemistr...arrow_drop_down
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    Authors: Lampilahti, Janne; Manninen, Hanna Elina; Leino, Katri; Väänänen, Riikka; +12 Authors

    Recent studies have shown the importance of new particle formation (NPF) to global cloud condensation nuclei (CCN) production, as well as to air pollution in megacities. In addition to the necessary presence of low-volatility vapors that can form new aerosol particles, both numerical and observational studies have shown that the dynamics of the planetary boundary layer (BL) plays an important role in NPF. Evidence from field observations suggests that roll vortices might be favorable for inducing NPF in a convective BL. However, direct observations and estimates of the potential importance of this phenomenon to the production of new aerosol particles are lacking. Here we show that rolls frequently induce NPF bursts along the horizontal circulations and that the small clusters and particles originating from these localized bursts grow in size similar to particles typically ascribed to atmospheric NPF that occur almost homogeneously at a regional scale. We outline a method to identify roll-induced NPF from measurements and, based on the collected data, estimate the impact of roll vortices on the overall aerosol particle production due to NPF at a boreal forest site (83 % ± 34 % and 26 % ± 8 % overall enhancement in particle formation for 3 and 10 nm particles, respectively). We conclude that the formation of roll vortices should be taken into account when estimating particle number budgets in the atmospheric BL.

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    Authors: Räisänen, Petri; Makkonen, Risto; Kirkevåg, Alf; Debernard, Jens B.;

    Snow consists of non-spherical grains of various shapes and sizes. Still, in radiative transfer calculations, snow grains are often treated as spherical. This also applies to the computation of snow albedo in the Snow, Ice, and Aerosol Radiation (SNICAR) model and in the Los Alamos sea ice model, version 4 (CICE4), both of which are employed in the Community Earth System Model and in the Norwegian Earth System Model (NorESM). In this study, we evaluate the effect of snow grain shape on climate simulated by NorESM in a slab ocean configuration of the model. An experiment with spherical snow grains (SPH) is compared with another (NONSPH) in which the snow shortwave single-scattering properties are based on a combination of three non-spherical snow grain shapes optimized using measurements of angular scattering by blowing snow. The key difference between these treatments is that the asymmetry parameter is smaller in the non-spherical case (0.77–0.78 in the visible region) than in the spherical case ( ≈ 0.89). Therefore, for the same effective snow grain size (or equivalently, the same specific projected area), the snow broadband albedo is higher when assuming non-spherical rather than spherical snow grains, typically by 0.02–0.03. Considering the spherical case as the baseline, this results in an instantaneous negative change in net shortwave radiation with a global-mean top-of-the-model value of ca. −0.22 W m−2. Although this global-mean radiative effect is rather modest, the impacts on the climate simulated by NorESM are substantial. The global annual-mean 2 m air temperature in NONSPH is 1.17 K lower than in SPH, with substantially larger differences at high latitudes. The climatic response is amplified by strong snow and sea ice feedbacks. It is further demonstrated that the effect of snow grain shape could be largely offset by adjusting the snow grain size. When assuming non-spherical snow grains with the parameterized grain size increased by ca. 70 %, the climatic differences to the SPH experiment become very small. Finally, the impact of assumed snow grain shape on the radiative effects of absorbing aerosols in snow is discussed.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ The Cryosphere (TC)arrow_drop_down
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    Authors: M. Sipilä; T. Jokinen; T. Berndt; S. Richters; +16 Authors

    Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of the reaction of stabilized Criegee intermediates (sCIs) with SO2, atmospheric oxidation processes were thought to be dominated by a few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulfuric acid (H2SO4). The measured total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) /k(sCI + SO2), was determined at relative humidities of 10 and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0–2.4) × 1012 molecules cm−3 and nearly independent of the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster with the organic acids than with SO2; k(sCI + acid) / k(sCI + SO2) = (2.8 ± 0.3) for formic acid, and k(sCI + acid) / k(sCI + SO2) = (3.4 ± 0.2) for acetic acid. This finding indicates that sCIs can play a role in the formation and loss of other atmospheric constituents besides SO2.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Atmospheric Chemistr...arrow_drop_down
    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    https://doi.org/10.34657/1227...
    Article . 2014
    License: CC BY
    Data sources: Datacite
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      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Atmospheric Chemistr...arrow_drop_down
      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
      https://doi.org/10.34657/1227...
      Article . 2014
      License: CC BY
      Data sources: Datacite
      addClaim

      This Research product is the result of merged Research products in OpenAIRE.

      You have already added works in your ORCID record related to the merged Research product.
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