Browsing by Subject "Atmosphere"

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  • Zanatta, M.; Gysel, M.; Bukowiecki, N.; Mueller, T.; Weingartner, E.; Areskoug, H.; Fiebig, M.; Yttri, K. E.; Mihalopoulos, N.; Kouvarakis, G.; Beddows, D.; Harrison, R. M.; Cavalli, F.; Putaud, J. P.; Spindler, G.; Wiedensohler, A.; Alastuey, A.; Pandolfi, M.; Sellegri, K.; Swietlicki, E.; Jaffrezo, J. L.; Baltensperger, U.; Laj, P. (2016)
    A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (sigma(ap)) divided by elemental carbon mass concentration (m(EC)). sigma(ap) and m(EC) have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. sigma(ap) was determined using filter based absorption photometers and m(EC) using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of sigma(ap) at a wavelength of 637 nm vary between 0.66 and 1.3 Mm(-1) in southern Scandinavia, 3.7-11 Mm(-1) in Central Europe and the British Isles, and 2.3-2.8 Mm(-1) in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 mu g m(-3) in southern Scandinavia, 0.28 -1.1 in Central Europe and the British Isles, and 0.22-0.26 in the Mediterranean. Both sigma(ap) and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m(2) g(-1) (geometric standard deviation = 133) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as +/- 30-70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect. (C) 2016 The Authors. Published by Elsevier Ltd.
  • Saponaro, Giulia (2020)
    Finnish Meteorological Institute Contributions 156
    Clouds play a vital role in Earth’s energy balance by modulating atmospheric processes, thus it is crucial to have accurate information on their spatial and temporal variability. Furthermore, clouds are relevant in those processes involved in aerosol-cloud-radiation interactions. The work conducted and presented herein concentrates on the retrievals of cloud properties, as well as their application for climate studies. While remote sensing observation systems have been used to analyze the atmosphere and observe its changes for the last decades, climate models predict how climate will change in the future. Altogether, these sources of observations are needed to better understand cloud processes and their impact on climate. In this thesis aerosol and cloud properties from the three above mentioned sources are applied to evaluate their potential in representing cloud properties and applicability in climate studies on local, regional and global scales. One aim of this thesis focuses on evaluating cloud parameters from ground-based remote-sensing sensors and from climate models using the MODerate Imaging Spectroradiometer (MODIS) data as a reference dataset. It is found that ground-based measurements of liquid clouds are in good agreement with MODIS cloud droplet size while poor correlation is found in the amount of cloud liquid water due to the management of drizzle. The comparison of the cloud diagnostic from three climate models with MODIS data, enabled through the application of a satellite simulator, helped to understand discrepancies among models, as well as discover deficiencies in their simulation processes. These findings are important to further improve the parametrization of atmospheric constituents in climate models, therefore enhancing the accuracy of climate projections. In this thesis it is also assessed the impact of aerosol particles on clouds. Satellite data can be used to derive climatically crucial quantities that are otherwise not directly retrieved (such as aerosol index and cloud droplet number concentration) which can be used to infer the sensitivity of clouds to aerosols changes. Results on the local and regional scales show that contrasting aerosol backgrounds indicate a higher sensitivity of clouds to aerosol changes in cleaner ambient air and a lower sensitivity in polluted areas, further corroborating the notion that anthropogenic emission modify clouds. On the global scale, the estimates of the aerosol-cloud interaction present, overall, a good agreement between the satellite- and model-based values which are in line with the results from other models.
  • Vazquez, L; Harri, A-M; Genzer, M (Finnish Meteorological Institute, 2017)
    Raportteja – Rapporter – Reports 2017:5
    The “ExoMars Atmospheric Science and Missions” Workshop served as a forum for general discussions on Martian atmospheric science with a focus on the assessment of the results and instrumentation development cycle of the ExoMars 2016 mission. These led to presentations and discussions of the atmospheric investigation plans and strategies for the ESA ExoMars-2020 mission in particular and for forthcoming Mars missions in general. The workshop gave overviews of the ExoMars atmospheric investigations through invited talks by Exomars scientists. The ExoMars atmospheric results and planned investigations were covered by individual scientific presentations. The workshop engaged early career scientists, inclusiveness states and scientific and technological cooperation in the European planetary science community. The Workshop provided a forum for discussion and debate on the outstanding scientific topics of the Martian atmosphere, and on how to integrate and network the scientific teams with providers of instruments and technical systems. Thus the workshop also contributed to international cooperation in the field of Martian atmospheric science and technology.
  • Kyllönen, Katriina (2020)
    Aerosols are well known to have effects on climate and human health. The chemical composition of aerosols in particular has a profound effect on the latter. Many trace elements (e.g. cadmium, lead and arsenic) found in the particulates as well as mercury (existing mostly in the gaseous form) are considered toxic for humans while deposition of these elements poses risks to the ecosystems. Due to emission abatement strategies, emissions of trace elements have significantly reduced in the recent decades. The overall objective of this thesis was to gain knowledge on the different sources as well as the temporal and spatial changes of atmospheric trace elements in Finland. The thesis was focused on the priority trace element pollutants mercury, arsenic, cadmium, nickel and lead. Also, other elements of interest were studied (aluminium, chromium, cobalt, copper, iron, manganese, vanadium, and zinc). Gaseous, particulate and deposition forms of the elements were investigated. The work was concentrated in background areas far away from possible anthropogenic sources; however, urban and industrial sites were also surveyed. The measurement techniques were partially developed or further validated in this thesis, and partially we utilised measurements conducted as a part of international measurement programmes. Sources of trace elements were studied with source apportionment method using positive matrix factorisation (PMF) and enrichment factors. Enrichment factors were used to characterize the source of a pollutant between natural and anthropogenic, and this grouped the elements from mainly crustal (Al, Fe) to highly anthropogenic origin (As, Cd, Pb, Zn) and others in between. PMF produced a more precise analysis of sources for Pallas, in which trace elements were associated with soil, sea emissions, and various long-range transported sources e.g. copper and nickel smelters in Kola Peninsula, Russia. In addition, magnitude of mercury soil and wetland emissions was investigated at one background site with the chamber technique. The air-terrestrial surface exchange measurements of elemental mercury showed that the soil emissions were found similar to depositional fluxes at the site (but opposite) and larger than the ones observed at wetland. For most trace elements, a clear south-to-north decreasing gradient in both atmospheric concentrations and deposition was observed due to minor local sources and longer distance to the large European source areas in the north than in the south. Additionally, the differences in the length of the snow-cover period have an effect on resuspension of some of the elements. For several elements both in particulate matter (PM) and deposition, statistically significant decreasing trends up to 80 % were detected since the 1990s. For gaseous mercury, no statistically significant trends were found. No statistically significant increasing trends were observed for PM, however, at two sites increases in deposition of single elements were detected. *** Ilmakehän hiukkasilla on tunnetusti vaikutuksia ilmastoon ja ihmisten terveydelle. Erityisesti näiden hiukkasten kemiallinen koostumus vaikuttaa jälkimmäiseen. Monien ilmakehässäkin esiintyvien raskasmetallien (kuten elohopean, kadmiumin ja lyijyn) tiedetään olevan myrkyllisiä ihmiselle, kun taas näiden laskeuma aiheuttaa haittaa ekosysteemeille. Päästövähennystoimenpiteiden myötä raskasmetallien päästöt ovat yleisesti vähentyneet viime vuosikymmeninä. Tämän väitöskirjan yleisenä tavoitteena oli selvittää ilmakehän raskasmetallien lähteitä sekä ajallisia ja maantieteellisiä trendejä Suomessa. Tutkimus keskittyi erityisen haitallisiin alkuaineisiin elohopeaan, arseeniin, kadmiumiin, nikkeliin ja lyijyyn. Myös alumiini, koboltti, kromi, kupari, mangaani, rauta, sinkki ja vanadiini olivat selvityksen kohteena. Väitöskirjassa on tutkittu näiden esiintymistä kaasumaisena, hiukkasiin sitoutuneena ja laskeumassa keskittyen kaukana päästölähteitä sijaitseviin tausta-alueisiin. Myös kaupunki- ja teollisuusympäristöt olivat kohteena. Tutkimuksessa käytettiin itse kehitettyjä tai validoituja mittausjärjestelmiä sekä kansainvälisissä mittausohjelmissa kerättyä tietoa. Raskasmetallien lähteitä tutkittiin kahdella lähdeanalyysillä. Rikastumiskertoimilla metallit jaettiin luonnosta ja ihmistoiminnasta peräisiin, ja analyysin perusteella suurin osa metalleista oli selvästi peräisin antropogeenisistä lähteistä, kun taas muutamat maaperän pölyämisestä. Yhdellä mittausasemista (Pallas) tutkittiin tarkemmin lähteitä positiivisen matriisin faktoroinnilla (PMF), jonka perusteella raskasmetallien lähteiksi tunnistettiin maaperän pölyäminen, meri, sekä erilaisia kaukokulkeumana vaikuttavia lähteitä, kuten kupari-nikkelisulatot Kuolan niemimaalla. Lisäksi elohopeatasetta tutkittiin ilmakehän ja maaperän/suon välillä kammiomenetelmällä yhdellä eteläisistä tausta-asemista. Tutkimuksessa havaittiin, että elohopeaa haihtui enemmän metsämaasta kuin suolta, ja metsämaasta haihtunut elohopean määrä vastasi karkeasti maahan laskeuman mukana kertynyttä osuutta. Useimpien raskasmetallien ilmapitoisuudet ja laskeuma kohosivat pohjoisesta etelään päin johtuen eroista paikallisissa päästöissä sekä pidemmästä etäisyydestä Euroopan suuriin päästöalueisiin. Myös etelän pohjoista lyhyempi lumikausi vaikutti joidenkin metallien pitoisuuksiin kohottavasti. Useimpien raskasmetallien ilmapitoisuuksien ja laskeuman todettiin vähentyneen tilastollisesti merkitsevästi, enimmillään 80 % 1990-luvun lopusta vuoteen 2018. Sen sijaan kaasumaisen elohopean pitoisuuksissa ei havaittu tilastollisesti merkitseviä muutoksia. Tilastollisesti merkitsevää ilmapitoisuuden nousua ei havaittu millään tutkituista metalleista pohjoisella mittausasemalla; sen sijaan laskeuman osalta kahdella mittausasemalla havaittiin yksittäisten alkuaineiden nousua.
  • Zilitinkevich, Sergej; Kadantsev, Evgeny; Repina, Irina; Mortikov, Evgeny; Glazunov, Andrey (2021)
    Turbulence is ever produced in the low-viscosity/large-scale fluid flows by velocity shears and, in unstable stratification, by buoyancy forces. It is commonly believed that both mechanisms produce the same type of chaotic motions, namely, the eddies breaking down into smaller ones and producing direct cascade of turbulent kinetic energy and other properties from large to small scales toward viscous dissipation. The conventional theory based on this vision yields a plausible picture of vertical mixing and has remained in use since the middle of the twentieth century in spite of increasing evidence of the fallacy of almost all other predictions. This paper reveals that in fact buoyancy produces chaotic vertical plumes, merging into larger ones and producing an inverse cascade toward their conversion into the self-organized regular motions. Herein, the velocity shears produce usual eddies spreading in all directions and making the direct cascade. This new paradigm is demonstrated and proved empirically; so, the paper launches a comprehensive revision of the theory of unstably stratified turbulence and its numerous geophysical or astrophysical applications.
  • Heiskanen, Jouni; Bruemmer, Christian; Buchmann, Nina; Calfapietra, Carlo; Chen, Huilin; Gielen, Bert; Gkritzalis, Thanos; Hammer, Samuel; Hartman, Susan; Herbst, Mathias; Janssens, Ivan A.; Jordan, Armin; Juurola, Eija; Karstens, Ute; Kasurinen, Ville; Kruijt, Bart; Lankreijer, Harry; Levin, Ingeborg; Linderson, Maj-Lena; Loustau, Denis; Merbold, Lutz; Myhre, Cathrine Lund; Papale, Dario; Pavelka, Marian; Pilegaard, Kim; Ramonet, Michel; Rebmann, Corinna; Rinne, Janne; Rivier, Leonard; Saltikoff, Elena; Sanders, Richard; Steinbacher, Martin; Steinhoff, Tobias; Watson, Andrew; Vermeulen, Alex T.; Vesa, Timo A.; Vitkova, Gabriela; Kutsch, Werner (2022)
    Since 1750, land-use change and fossil fuel combustion has led to a 46% increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limit global temperature increases to well below 2 degrees C above preindustrial levels. Increasing levels of CO2 and other greenhouse gases (GH6s), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere are sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature, and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers' decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface, and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.