Ari J Asmi

Ari J Asmi
University of Helsinki | HY · Department of Physics

PhD

About

81
Publications
12,615
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4,308
Citations
Additional affiliations
January 2004 - present
University of Helsinki

Publications

Publications (81)
Article
Full-text available
A dataset, small or big, is often changed to correct errors, apply new algorithms, or add new data (e.g., as part of a time series), etc. In addition, datasets might be bundled into collections, distributed in different encodings or mirrored onto different platforms. All these differences between versions of datasets need to be understood by resear...
Technical Report
Full-text available
Executive Summary The demand for better reproducibility of research results is growing. With more data becoming available online, it will become increasingly important for a researcher to be able to cite the exact extract of the data set that was used to underpin their research publication. However, while the means to identify datasets using persis...
Technical Report
Full-text available
Data versioning is a fundamental element to ensuring the reproducibility of research. Work in other RDA groups on data provenance and data citation, as well as the W3C Dataset Exchange Working Group, have highlighted that definitions of data versioning concepts and recommended practices are still missing. An important driver to more closely examin...
Article
Full-text available
PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile or...
Article
Full-text available
PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile or...
Article
Full-text available
The formation of new atmospheric particles involves an initial step forming stable clusters less than a nanometre in size (<~1 nm), followed by growth into quasi-stable aerosol particles a few nanometres (~1-10 nm) and larger (>~10 nm). Although at times, the same species can be responsible for both processes, it is thought that more generally each...
Article
Full-text available
The terrestrial biosphere is an important source of natural aerosol. Natural aerosol sources alter climate, but are also strongly controlled by climate, leading to the potential for natural aerosol–climate feedbacks. Here we use a global aerosol model to make an assessment of terrestrial natural aerosol–climate feedbacks, constrained by observation...
Article
Full-text available
This study explores the vertical and horizontal variability of the particle number size distribution from two flight measurements campaigns over a boreal forest in Hyytiälä, Finland during May–June 2013 and March–April 2014, respectively. Our other aims were to study the spatial extent of new particle formation events and to compare the airborne ob...
Article
Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN...
Article
Full-text available
New-particle formation (NPF) is globally an important source of climatically-relevant atmospheric aerosols. Here we explore the inter-annual variability and trends in sources and sinks of atmospheric nanoparticles in a boreal forest environment. We look into the precursor vapors leading to the aerosol formation, NPF frequency, as well as the format...
Article
Full-text available
Environmental Research infrastructures are facilities, resources, systems and related services that are used by research communities to conduct top-level research. They are designed as long‐term entities in order to meet the requirements of continuous environmental observation. This longevity makes the environmental research infrastructures ideal s...
Article
Full-text available
The smelter industry in Kola Peninsula is the largest source of anthropogenic SO2 in the Arctic part of Europe and one of the largest within the Arctic domain. Due to socio-economic changes in Russia, the emissions have been decreasing especially since the late 1990s resulting in decreased SO2 concentrations close to Kola in eastern Lapland, Finlan...
Article
Full-text available
Cluster analysis of particle number size distributions from background sites across Europe is presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was ident...
Article
Full-text available
Many of the next generation of global climate models will include aerosol schemes which explicitly simulate the microphysical processes that determine the particle size distribution. These models enable aerosol optical properties and cloud condensation nuclei (CCN) concentrations to be determined by fundamental aerosol processes, which should lead...
Article
Full-text available
Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN...
Article
Full-text available
The smelter industry in Kola Peninsula is the largest source of anthropogenic SO2 in the Arctic part of Eurasia and one of the largest within the Arctic domain. Due to socio-economic changes in Russia the emissions have been decreasing especially since the late 1990s resulting in decreased SO2 concentrations close to Kola in Eastern Lapland, Finlan...
Article
Full-text available
Ambient aerosol, CCN (cloud condensation nuclei) and hygroscopic properties were measured with a size-segregated CCNC (cloud condensation nuclei counter) in a boreal environment of southern Finland at the SMEAR (Station for Measuring Ecosystem-Atmosphere Relations) II station. The instrumental setup operated at five levels of supersaturation S cove...
Article
Full-text available
The capability to accurately yet efficiently represent atmospheric nanoparticle growth by biogenic and anthropogenic secondary organics is a challenge for current atmospheric large-scale models. It is, however, crucial to predict nanoparticle growth accurately in order to reliably estimate the atmospheric cloud condensation nuclei (CCN) concentrati...
Technical Report
Full-text available
In the age of data driven science the re­use of data and the compilation of existing data from monitoring infrastructures has become an integral part of research. For the sake of transparency and reproducibility of research it is crucial to be able to unambiguously identify data that were used as the basis of a publication. Globally unique and reso...
Article
Atmospheric aerosol particles influence the climate system directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Apart from black carbon aerosol, aerosols cause a negative radiative forcing at the top of the atmosphere and substantially mitigate the warming caused by greenhouse gases. In the fu...
Article
A global climate model is being run to study the consequences of Brazil transitioning from fossil to biofuels over the next few decades. Assuming all other factors constant, preliminary results suggest little to no climatic relevance.
Article
Ambient aerosol CCN and hygroscopic properties were measured with a size-segregated CCNc in a boreal environment of Southern Finland at the SMEAR II station since February 2009. The overall median critical diameter Dc for CCN activation is reported at 75 nm, exhibiting a clear maximum in February and a minimum in July. The overall median aerosol hy...
Conference Paper
Many of the next generation of climate models will include aerosol schemes which explicitly simulate the microphysical processes that determine the particle size distribution. Such aerosol microphysics schemes ensure that aerosol optical properties and cloud condensation nuclei concentrations are determined by fundamental aerosol processes, which s...
Article
Full-text available
Ambient aerosol, CCN and hygroscopic properties were measured with a size-segregated CCNC in a~boreal environment of Southern Finland at the SMEAR II station. The instrumental setup operated at five levels of supersaturation S covering a range from 0.1 to 1% and measured particles with a size range of 20-300 nm; a total of 29 non-consecutive months...
Article
Full-text available
The capability to accurately yet efficiently represent atmospheric nanoparticle growth by biogenic and anthropogenic secondary organics is a challenge for current atmospheric large-scale models. It is, however, crucial to predict nanoparticle growth accurately in order to reliably estimate the atmospheric cloud condensation nuclei (CCN) concentrati...
Article
Full-text available
We have analysed the trends of total aerosol parti-cle number concentrations (N) measured at long-term mea-surement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarc-tica, and on Pacific Ocean islands. The majority of the sites showed clear d...
Article
Full-text available
Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (>10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelen...
Article
Full-text available
Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavele...
Article
Full-text available
This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent cloud condensation nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both...
Chapter
The aerosol particle number size distribution is a key component in aerosol indirect climate effects, and is also a key factor on potential nanoparticle health effects. This chapter will give background on particle number size distributions, their monitoring and on potential climate and health effects of submicron aerosol particles. The main intere...
Article
Full-text available
The biosphere emits volatile organic compounds (BVOCs) which, after oxidation in the atmosphere, can partition on the existing aerosol population or even form new particles. The large quantities emitted provide means for a large potential impact on both aerosol direct and indirect effects. Biogenic responses to atmospheric temperature change can es...
Article
Full-text available
We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decr...
Article
Full-text available
This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent Cloud Condensation Nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both...
Article
Weekday related anthropogenic aerosol emissions have been suggested to affect regional climate via indirect aerosol effects. I studied the variability of potential cloud condensation nuclei using measurements of number size distributions of Cloud Condensation Nuclei (CCN)-sized aerosol particles and CCNs measured at several European regional backgr...
Article
Full-text available
The biosphere emits volatile organic compounds (BVOCs) which, after oxidation in the atmosphere, can partition on the existing aerosol population or even form new particles. The large quantities emitted provide means for a large potential impact on both aerosol direct and indirect effects. Biogenic responses to atmospheric temperature change can es...
Article
Atmospheric aerosols often contain surface active organics. We study the influence of these surfactants on predictions of particle cloud activation potential and aerosol indirect climate effects, by implementing different parametrizations of surfactant effects in the global circulation model ECHAM5.5-HAM2. A parametrization based only on droplet su...
Article
Full-text available
The number concentration of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle forma...
Article
Full-text available
In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties...
Article
Full-text available
The online-coupled, regional chemistry transport model COSMO-ART is evaluated for periods in all seasons against several measurement datasets to assess its ability to represent gaseous pollutants and ambient aerosol characteristics over the European domain. Measurements used in the comparison include long-term station observations, satellite and gr...
Article
Full-text available
The number of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle formation on anthro...
Article
Full-text available
The online-coupled, regional chemistry transport model COSMO-ART is evaluated for periods in all seasons against several measurement datasets to assess its ability to represent gaseous pollutants and ambient aerosol characteristics over the European domain. Measurements used in the comparison include long-term station observations, satellite and gr...
Article
Full-text available
In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties...
Article
Full-text available
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 and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aer...
Article
Full-text available
In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties...
Article
Full-text available
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 and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aer...
Article
Full-text available
In anthropogenically influenced atmospheres, sulphur dioxide (SO<sub>2</sub>) is the main precursor of gaseous sulphuric acid (H<sub>2</sub>SO<sub>4</sub>), which in turn is a main precursor for atmospheric particle nucleation. As a result of socio-economic changes, East Germany has seen a dramatic decrease in anthropogenic SO<sub>2</sub> emissions...
Article
Full-text available
In anthropogenically influenced atmospheres, sulphur dioxide (SO2) is the main precursor of gaseous sulphuric acid (H2SO4), which in turn forms new aerosol particles (diameter 2 emissions between 1989 and present, as documented by routine air quality measurements in many locations. Using two different data sets of experimental particle number size...
Article
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No abstract available.
Article
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The European Aerosol Cloud Climate and Air Quality Interactions project EUCAARI is an EU Research Framework 6 integrated project focusing on understanding the interactions of climate and air pollution. EUCAARI works in an integrative and multidisciplinary way from nano- to global scale. EUCAARI brings together several leading European research grou...