Browsing Faculty of Natural and Agricultural Sciences by Author "Laakso, L."
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Ambient aromatic hydrocarbon measurements at Welgegund, South Africa
Jaars, K.; Beukes, J.P.; Van Zyl, P.G.; Venter, A.D.; Josipovic, M.; Pienaar, J.J.; Tiitta, P.; Laakso, L. (EGU, 2014)Aromatic hydrocarbons are associated with direct adverse human health effects and can have negative impacts on ecosystems due to their toxicity, as well as indirect negative effects through the formation of tropospheric ... -
The anthropogenic contribution to atmospheric black carbon concentrations in southern Africa: a WRF-Chem modeling study
Kuik, F.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Laakso, L.; Lauer, A.; Vakkari, V. (EGU, 2015)South Africa has one of the largest industrialized economies in Africa. Emissions of air pollutants are particularly high in the Johannesburg-Pretoria metropolitan area, the Mpumalanga Highveld and the Vaal Triangle, ... -
Atmospheric boundary layer top height in South Africa: measurements with lidar and radiosonde compared to three atmospheric models
Korhonen, K.; Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Tiitta, P. (EGU, 2014)Atmospheric lidar measurements were carried out at Elandsfontein measurement station, on the eastern Highveld approximately 150 km east of Johannesburg in South Africa throughout 2010. The height of the planetary ... -
Atmospheric ions and nucleation: a review of observations
Hirsikko, T.; Laakso, L.; Nieminen, S.; Gagné, S.; Lehtipalo, K. (EGU, 2011)This review is based on ca. 260 publications, 93 of which included data on the temporal and spatial variation of the concentration of small ions (<1.6 nm in diameter) especially in the lower troposphere, chemical composition, ... -
Basic characteristics of atmospheric particles, trace gases and meteorology in a relatively clean Southern African Savannah environment
Laakso, L.; Pienaar, K.; Laakso, H.; Aalto, P.P.; Keronen, P. (EGU, 2008)We have analyzed one year (July 2006–July 2007) of measurement data from a relatively clean background site located in dry savannah in South Africa. The annualmedian trace gas concentrations were equal to 0.7 ppb for SO2, ... -
Boundary layer nucleation as a source of new CCN in savannah environment
Laakso, L.; Merikanto, J.; Vakkari, V.; Molefe, M.; Kgabi, N. (EGU, 2013)The South African savannah region is a complex environment of air pollution and natural emissions influenced by a strong seasonal cycle in biomass burning and strong precipitation. However, the scarcity of long-term ... -
Characterisation of sub-micron particle number concentrations and formation events in the western Bushveld Igneous Complex, South Africa
Hirsikko, A.; Tiitta, P.; Beukes, J.P.; Laakso, L.; Vakkari, V. (EGU, 2012)South Africa holds significant mineral resources, with a substantial fraction of these reserves occurring and being processed in a large geological structure termed the Bushveld Igneous Complex (BIC). The area is also ... -
Characterization of satellite-based proxies for estimating nucleation mode particles over South Africa
Sundström, A.-M.; Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Venter, A.D.; Jaars, K.; Pienaar, J.J.; Piketh, S.; Chiloane, E.K. (EGU, 2015)Proxies for estimating nucleation mode number concentrations and further simplification for their use with satellite data have been presented in Kulmala et al. (2011). In this paper we discuss the underlying assumptions ... -
Chemical composition, main sources and temporal variability of PM1 aerosols in southern African grassland
Tiitta, P.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Venter, A.D.; Jaars, K.; Pienaar, J.J.; Laakso, L. (EGU, 2014)Southern Africa is a significant source region of atmospheric pollution, yet long-term data on pollutant concentrations and properties from this region are rather limited. A recently established atmospheric measurement ... -
Climate and air quality trade-offs in altering ship fuel sulfur content
Partanen, A.I.; Laakso, L.; Laakso, A .; Schmidt, A.; Kokkola, H. (EGU, 2013)Aerosol particles from shipping emissions both cool the climate and cause adverse health effects. The cooling effect is, however, declining because of shipping emission controls aiming to improve air quality. We used an ... -
Correction for a measurement artifact of the Multi-Angle Absorption Photometer (MAAP) at high black carbon mass concentration levels
Hyvärinen, A.-P.; Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Garland, R.M. (EGU, 2013)The Multi-Angle Absorption Photometer (MAAP) is a widely-used instrument for aerosol black carbon (BC) measurements. In this paper, we show correction methods for an artifact found to affect the instrument accuracy in ... -
Differences in aerosol absorption Ångström exponents between correction algorithms for a particle soot absorption photometer measured on the South African Highveld
Backman, J.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Piketh, S.; Tiitta, P.; Chiloane, K.; Laakso, L. (European Geosciences Union, 2014)Absorption Ångström exponents (AAEs) calculated from filter-based absorption measurements are often used to give information on the origin of the ambient aerosol, for example, to distinguish between urban pollution ... -
Estimating the concentration of nucleation mode aerosol particles over South Africa using satellite remote sensing measurements
Sundström, A.-M.; Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Venter, A.D.; Jaars, K.; Pienaar, J.J.; Piketh, S.; Chiloane, E.K. (AIP Publishing, 2013)In this work satellite based observations were used to estimate the concentration of nucleation mode aerosols over South Africa. The nucleation mode aerosols can not be detected directly with satellite instruments since ... -
General overview: European integrated project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI): integrating aerosol research from nano to global scales
Kulmala, M.; Beukes, J.P.; Josipovic, M.; Laakso, L.; Pienaar, J.J.; Van Zyl, P.G. (EGU, 2011)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 ... -
Long-term observations of aerosol size distributions in semi-clean and polluted savannah in South Africa
Vakkari, V.; Beukes, J.P.; Mabaso, D.; Pienaar, J.J.; Laakso, L. (EGU, 2013)This study presents a total of four years of sub-micron aerosol particle size distribution measurements in the southern African savannah, an environment with few previous observations covering a full seasonal cycle and the ... -
Measurements of aerosol charging states in Helsinki, Finland
Gagné, S.; Laakso, L.; Leppä, J.; Petäjä, T.; McGrath, M.J (EGU, 2011)The charging state of aerosol populations was measured with an Ion-DMPS in Helsinki, Finland between December 2008 and February 2010. Based on the charging states, we calculated the ion-induced nucleation fraction to be ... -
Multiple daytime nucleation events in semi-clean savannah and industrial environments in South Africa: analysis based on observations
Hirsikko, A.; Vakkari, V.; Tiitta, P.; Beukes, J.P.; Laakso, L. (EGU, 2013)Recent studies have shown very high frequencies of atmospheric new particle formation in different environments in South Africa. Our aim here was to investigate the causes for two or three consecutive daytime nucleation ... -
New particle formation events in semi-clean South African savannah
Vakkari, V.; Laakso, L.; Laakso, H.; Kulmala, M.; Mabaso, D. (EGU, 2010)This study is based on 18 months (20 July 2006–5 February 2008) of continuous measurements of aerosol particle size distributions, air ion size distributions, trace gas concentrations and basic meteorology in a semi-clean ... -
One year of Raman lidar observations of free-tropospheric aerosol layers over South Africa
Giannakaki, E.; Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Josipovic, M.; Tiitta, P.; Piketh, S. (EGU, 2015)Raman lidar data obtained over a 1 year period has been analysed in relation to aerosol layers in the free troposphere over the Highveld in South Africa. In total, 375 layers were observed above the boundary layer during ... -
South African EUCAARI measurements: seasonal variation of trace gases and aerosol optical properties
Laakso, L.; Beukes, J.P.; Van Zyl, P.G.; Tiitta, P.; Josipovic, M.; Pienaar, J.J. (EGU, 2012)In this paper we introduce new in situ observations of atmospheric aerosols, especially chemical composition, physical and optical properties, on the eastern brink of the heavily polluted Highveld area in South Africa. ...