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Columnar Modelling of Nucleation Burst Evolution in the Convective Boundary Layer ? first Results from a Feasibility Study Part I: Modelling Approach O

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Columnar Modelling of Nucleation Burst Evolution in the Convective Boundary Layer ? first Results from a Feasibility Study Part I: Modelling Approach O View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by HAL-INSU Columnar modelling of nucleation burst evolution in the convective boundary layer ? first results from a feasibility study Part I: Modelling approach O. Hellmuth To cite this version: O. Hellmuth. Columnar modelling of nucleation burst evolution in the convective boundary layer ? first results from a feasibility study Part I: Modelling approach. Atmospheric Chemistry and Physics, European Geosciences Union, 2006, 6 (12), pp.4175-4214. <hal-00296029> HAL Id: hal-00296029 https://hal.archives-ouvertes.fr/hal-00296029 Submitted on 21 Sep 2006 HAL is a multi-disciplinary open access L'archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destin´eeau d´ep^otet `ala diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publi´esou non, lished or not. The documents may come from ´emanant des ´etablissements d'enseignement et de teaching and research institutions in France or recherche fran¸caisou ´etrangers,des laboratoires abroad, or from public or private research centers. publics ou priv´es. Atmos. Chem. Phys., 6, 4175–4214, 2006 www.atmos-chem-phys.net/6/4175/2006/ Atmospheric © Author(s) 2006. This work is licensed Chemistry under a Creative Commons License. and Physics Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part I: Modelling approach O. Hellmuth Leibniz Institute for Tropospheric Research, Modelling Department, Permoserstrasse 15, 04318 Leipzig, Germany Received: 1 August 2005 – Published in Atmos. Chem. Phys. Discuss.: 10 November 2005 Revised: 14 February 2006 – Accepted: 11 May 2006 – Published: 21 September 2006 Abstract. A high-order modelling approach to interpret essentially extended by Charlson, Lovelock, Andrea and “continental-type” particle formation bursts in the anthro- Warren2 (Charlson et al., 1987). In their postulated neg- pogenically influenced convective boundary layer (CBL) is ative feedback mechanism, abundant atmospheric sulphate proposed. The model considers third-order closure for plane- aerosols are hypothesised to play a key role in stabilising tary boundary layer turbulence, sulphur and ammonia chem- Earth’s climate. An assumed global warming, caused by ra- istry as well as aerosol dynamics. In Paper I of four papers, diative forcing of greenhouse gases, would lead to an in- previous observations of ultrafine particle evolution are re- crease of the sea surface temperature and, consequently, to viewed, model equations are derived, the model setup for a an increase of dimethyl sulphide emissions (DMS, (CH3)2S) conceptual study on binary and ternary homogeneous nucle- from marine phytoplankton (e.g., macroalgae) into the at- ation is defined and shortcomings of process parameterisa- mosphere. The gas phase oxidation of DMS produces sul- tion are discussed. In the subsequent Papers II, III and IV phur dioxide (SO2), which further oxidises with the hydroxyl simulation results, obtained within the framework of a con- radical (OH) to form sulphuric acid (H2SO4). According to ceptual study on the CBL evolution and new particle forma- the present level of process understanding, H2SO4 vapour tion (NPF), will be presented and compared with observa- and water (H2O) vapour are key precursor gases for the ho- tional findings. mogeneous heteromolecular (binary) nucleation of sulphate aerosols over the ocean. Due to condensation and coagulation processes, these microscopic particles can grow via interme- 1 Introduction diate, not yet fully understood stages from so-called ther- modynamically stable clusters (TSCs) (Kulmala et al., 2000; At the end of the 1960’s, James Lovelock came up with an Kulmala, 2003) via ultrafine condensation nuclei (UCNs) to influential theory of homeostasis of a fictive planet Gaia, rep- non-sea-salt (nss) sulphate aerosols and, finally, to cloud con- resented by the conceptual “daisyworld” model (Lovelock, densation nuclei (CCNs). An increase of the CCN concen- 1993). Lovelock proposed a negative feedback mechanism tration leads to an enhancement of the number concentra- to explain the relative stability of Earth’s climate over geo- tion of cloud droplets. According to an effect proposed by logical times, which became generally known as “Gaia hy- Twomey (1974), a higher cloud droplet concentration causes pothesis”1. At the end of the 1980’s, the Gaia theory was an enhancement of the cloud reflectivity for a given liquid water content. An increased reflectivity of solar radiation Correspondence to: O. Hellmuth by clouds cools the atmosphere and counteracts the initial ([email protected]) warming. Via this route, a thermal stabilisation of Earth’s 1 In the Hellenistic mythology, “Gaia” is the name of the god- climate is accomplished. For the illustration of this theory hood of Earth. James Lovelock and the Nobel prize winner William the reader is referred, e.g., to Easter and Peters (1994) and Golding used this name as a synonym for a self-regulating geophys- Brasseur et al. (2003, pp. 142–143, Fig. 4.10). Apart from ical and biophysical mechanism on a global scale. According to the Gaia hypothesis, temperature, oxidation state, acidity as well as their climate impact, aerosol particles are also affecting hu- different physicochemical parameters of rocks and waters remain man health, visibility etc. constant at each time due to homeostatic interactions, maintained by massive feedback processes. These feedback processes are initi- gle creatures). ated by the “living world”, whereas the equilibrium conditions are 2According to the initials of the authors, this theory became changing dynamically with the evolution of Earth’s live (not of sin- known as CLAW hypothesis. Published by Copernicus GmbH on behalf of the European Geosciences Union. 4176 O. Hellmuth: Burst modelling Recently, Kulmala et al. (2004c, Fig. 1) proposed a pos- cloud condensation nuclei”4 (Kulmala et al., 2000, p. 66). sible connection between the carbon balance of ecosys- Depending on the availability of pre-existing particles and/or tems and aerosol-cloud-climate interactions, also suspected condensable vapours, Kulmala et al. (2000) hypothesised two to play a significant role in climate stabilisation. Increas- possibilities for the growth of TSC particles to detectable ing carbon dioxide (CO2) concentrations accelerate photo- size: (a) When the concentration of pre-existing particles is synthesis, which in turn consumes more CO2. But forest low, TSCs can effectively grow by self-coagulation. (b) In the ecosystems also act as significant sources of atmospheric presence of a high source of available condensable vapours aerosols via enhanced photosynthesis-induced emissions of (e.g., organics, inorganics, NH3) TSCs can effectively grow non-methane biogenic volatile organic compounds (BVOCs) to detectable size and even to Aitken mode size by condensa- from vegetation3. Owing to the capability of BVOCs to get tion. By means of the advanced sectional aerosol dynamical activated into CCNs, biogenic aerosol formation may also model AEROFOR the authors concluded, that ternary nucle- serve as negative feedback mechanism in the climate system, ation is able to produce a high enough reservoir of TSCs, slowing down the global warming similar as proposed in the which can grow to detectable size and subsequently being CLAW hypothesis. able to explain observed particle formation bursts in the at- mosphere. The occurrence of bursts was demonstrated to be connected to the activation of TSCs with extra condensable 2 Key mechanisms of new particle formation in the at- vapours (e.g., after advection over sources or mixing). Ion- mosphere induced nucleation was ruled out as a TSC formation path- way because of the typically low ionisation rate in the tro- Atmospheric NPF is known to widely and frequently occur in posphere. Later on, this concept has been advanced by Kul- Earth’s atmosphere. It is generally accepted to be an essen- mala (2003). The author refers to four main nucleation mech- tial process, which must be better understood and included anisms, which are suspected to be relevant for NPF in the in global and regional climate models (Kulmala, 2003). So atmosphere: far, the most comprehensive review of observations and phe- nomenological studies of NPF, atmospheric conditions under 1. Homogeneous nucleation involving binary mixtures which NPF has been observed, and empirical nucleation rates of H2O and H2SO4 (occurrence, e.g., in industrial etc. over the past decade, from a global retrospective and plumes); from different sensor platforms was performed by Kulmala et al. (2004d). The authors reviewed altogether 149 studies 2. Homogeneous ternary H2O/H2SO4/NH3 nucleation and collected 124 observational references of NPF events in (occurrence in the CBL); the atmosphere. The elucidation of the mechanism, by which new parti- 3. Ion-induced nucleation of binary, ternary or organic cles nucleate and grow in the atmosphere, is of key impor- vapours (occurrence in the upper troposphere (UT) and tance to better understand these effects, especially the role lower stratosphere); of aerosols in climate control (Kulmala et al., 2000; Kul- 4. Homogeneous nucleation involving iodide species (oc- mala, 2003). Kulmala et al. (2000) pointed out, that in some currence in coastal environments). cases observed NPF rates can be adequately explained by binary nucleation involving H2O and H2SO4. But
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