Measurements of the relation between aerosol properties and microphysics and chemistry of low level liquid water clouds in Northern Finland

Lihavainen, Heikki; Kerminen, Veli‐Matti; Komppula, Mika; Hyvärinen, Antti; Laakia, Jaakko; Saarikoski, Sanna; Makkonen, Ulla; Kivekäs, Niku; Hillamo, Risto; Kulmala, Markku; Viisanen, Y.

doi:10.5194/acp-8-6925-2008

Cited by 40 publications

(47 citation statements)

References 57 publications

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“…The CCNs are not, however, linearly connected to CDNCs, as the water depletion and other cloud processes can increase the actual cut-off diameter of cloud activation. In field experiments done at the top of mountains, a semi-direct measurement of the activated fraction to CDNC can be sometimes made, with activation diameters observed from 40 nm to over 200 nm (Henning et al, 2002;Sellegri et al, 2003;Lihavainen et al, 2008). Nevertheless, fixed activation diameters have been used as surrogates in several CCN-to-CDNC parameterizations (e.g.…”

Section: Relevant Metrics and Properties Of Sub-micron Size Distributmentioning

confidence: 99%

Number size distributions and seasonality of submicron particles in Europe 2008–2009

et al. 2011

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Abstract.Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations Correspondence to: A. Asmi (ari.asmi@helsinki.fi) and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.Published by Copernicus Publications on behalf of the European Geosciences Union. We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-touse and freely available comparison dataset of aerosol size distributions.

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Section: Relevant Metrics and Properties Of Sub-micron Size Distributmentioning

confidence: 99%

Number size distributions and seasonality of submicron particles in Europe 2008–2009

et al. 2011

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“…Most of these measurements are performed at a clean background site in northern Finland, Pallas Kerminen et al, 2005;Lihavainen et al, 2008), which is at the northern border of the boreal forest. Recently, Lihavainen et al (2010) estimated aerosol-cloud interactions over Pallas, using a combination of ground-based and MODIS data of cloud and aerosol properties.…”

Section: Introductionmentioning

confidence: 99%

Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

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Abstract. Seasonal variations in cloud droplet number concentration (N CD ) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in N CD , obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that N CD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low N CD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surface.

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“…The time step for this resolution is 12 min. Large scale transport uses the Flux Form SemiLangrangian (FFSL) method by Lin and Rood (1996).…”

Section: Aerosol-climate Model Echam5-hammentioning

confidence: 99%

“…We have compared a subset of these measurements to the size distributions simulated with SALSA and M7. Figure 5 shows the modelled and observed annual median aerosol size distributions at six EUCAARI sites: Jungfraujoch (Jurnyi et al, 2011), Hyytiälä (Hari and Kulmala, 2005), Mace Head (Jennings et al, 1991), Aspvreten (Tunved et al, 2004), Melpitz (Engler et al, 2007) and Pallas (Lihavainen et al, 2008). These sites include coastal (Mace Head), mountain (Jungfraujoch), arctic (Pallas), boreal coniferous (Hyytiälä), urban polluted (Melpitz) and mixed boreal coniferous and deciduous (Aspvreten) locations.…”

Section: Surface Concentrations Of Particulate Massmentioning

confidence: 99%

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Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

et al. 2012

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Abstract. We present the implementation and evaluation of a sectional aerosol microphysics module SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by minimising the number of variables needed to describe the size and composition distribution. The aerosol size distribution is described using 10 size classes with parallel sections which can have different chemical compositions. Thus in total, the module tracks 20 size sections which cover diameters ranging from 3 nm to 10 µm and are divided into three subranges, each with an optimised selection of processes and compounds.The implementation of SALSA into ECHAM5-HAM includes the main aerosol processes in the atmosphere: emissions, removal, radiative effects, liquid and gas phase sulphate chemistry, and the aerosol microphysics. The aerosol compounds treated in the module are sulphate, organic carbon, sea salt, black carbon, and mineral dust. In its default configuration, ECHAM5-HAM treats aerosol size distribution using the modal method. In this implementation, the aerosol processes were converted to be used in a sectional model framework.The ability of the module to describe the global aerosol properties was evaluated by comparing against (1) measured continental and marine size distributions, (2) observed variability of continental number concentrations, (3) measured sulphate, organic carbon, black carbon and sea-salt mass concentrations, (4) observations of aerosol optical depth (AOD) and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7, which is the default aerosol microphysics module in ECHAM5-HAM.The evaluation shows that the global aerosol properties can be reproduced reasonably well using a coarse resolution of 10 sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sulphate and carbonaceous species have an annual mean within a factor of two of the observations. The simulated sea-salt concentrations reproduce the observations within a factor of two, apart from the Southern Ocean over which the concentrations are within a factor of five. Regionally, AOD is in a relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modelled AOD is significantly lower than observed.Regarding most of the investigated aerosol properties, the SALSA and the modal aerosol module M7 perform comparably well against observations. However, SALSA reproduces the observed number concentrations and the size distribution of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in...

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Measurements of the relation between aerosol properties and microphysics and chemistry of low level liquid water clouds in Northern Finland

Cited by 40 publications

References 57 publications

Number size distributions and seasonality of submicron particles in Europe 2008–2009

Number size distributions and seasonality of submicron particles in Europe 2008–2009

Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

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