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Atmospheric Sciences

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The main research activities are  i) climate change research, ii) climate change and air quality interactions, iii) aerosol and environmental physics, (iv) micrometeorology and forest-atmosphere relations, and (v) dynamical meteorology.

The core of the research is the understanding of energy, mass and momentum transfer and phase transitions. Theoretical, modelling and experimental studies of nucleation, condensation/evaporation and atmospheric aerosol dynamics have continued in 2012. Studies of deposition and fluxes of atmospheric gases, cloud microphysics, atmospheric radiation, mesoscale meteorology, and climate and radar meteorology were performed.

Researchers operate together with the researchers of the Department of Forest Sciences at versatile field stations: SMEAR I (Station for Measuring Forest Ecosystem-Atmosphere Relations) station in Värriö (Lapland), SMEAR II station in Hyytiälä, and SMEAR III (urban SMEAR) in Kumpula Campus. Particularly SMEAR II has turned out to be a leading station in its research field due to its comprehensive research program and to its unique time series of fresh aerosol formation. The development and construction of novel weather radar techniques has been performed in collaboration with Vaisala Oyj. The research at the Division is also linked with the instrumental development work with international companies. The most important one has been Aerodyne Research, Inc. in the U.S.A. The co-operation concerns development of high-response greenhouse gas analyzers and the aerosol mass spectroscopy technique.

The Finnish Centre of Excellence in "Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change" started its operation in 2008. The international Master programme "Atmosphere-Biosphere Studies" has continued its operation together with the national graduate school. The Nordic Centers of Excellence CRA-ICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate, coordinated by Markku Kulmala) and DEFROST (Impacts of a changing cryosphere - depicting eco-system-climate feedbacks from permafrost, snow and ice, Timo Vesala as a partner) started in 2010.

A project office "Integrated Land Ecosystem – Atmosphere Processes Study" (iLEAPS) has continued its work related to land-atmosphere interactions within the International Geosphere – Biosphere Programme (IGBP). The iLEAPS project aims at advancing new integrated experimental and modelling research approaches needed in the Earth System. We are also active in Future Earth initiative. The division is also in charge to establish national and European Integrated Carbon Observation System (ICOS). In 2012 the division started new initiative PEEX (Pan Eurasian Experiment).

The final report of EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions) was written in the first half of 2011. EUCAARI has 48 partners from 24 different countries and it was co-ordinated by the division. 

The researchers have co-ordinated and participated in several international projects. The researchers hosted 15 national and international workshops and conferences in 2012, organized more than 10 intensive measurement campaigns in Finland and abroad, the most important one being CLOUD (Cosmics Leaving OUtdoor Droplets) at CERN.

Highlights of research

A new atmospherically relevant oxidant discovered

Atmospheric oxidation is a key phenomenon that connects atmospheric chemistry with globally challenging environmental issues such as climate change, stratospheric ozone loss and acidification of soils and water. Oxidation processes remove many pollutants from the air and are thus essential for air cleanliness and the health effects of air quality. The dominant or even the only important atmospheric gas phase oxidants have been considered to be OH, O3 and NO3. We found, basing on atmospheric observations, supported by laboratory experiments and theoretical considerations, that there exists a compound X – very probably a stabilized Criegee intermediate – which has a significant capacity to oxidize atmospheric trace gases like SO2. This compound increases the reactivity of the atmosphere. Increased sulphuric acid production via this new oxidation pathway has consequences to atmospheric aerosol formation and thus potentially to whole atmospheric system. The oxidation chemistry of X seems to be connected tightly with the presence of alkenes, especially those emitted by the forests. Therefore, it is not surprising that this unexpected discovery was made in the boreal forest environment at the SMEAR II field station.

Reference:

Mauldin, III, R. L., Berndt, T., Sipilä, M., Paasonen, P., Petäjä, T., Kim, S., Kurten, T., Stratmann, F., Kerminen, V.-M., and Kulmala, M.: A new atmospherically relevant oxidant of sulphur dioxide, Nature, 488, 193-197, 2012.

Radiative absorption enhancements due to the mixing state of atmospheric black carbon

Atmospheric black carbon (BC) warms Earth”s climate, and its reduction has been targeted for near-term climate change mitigation. Quantification of the warming caused by BC is typically assessed with global climate models. Our measurements onboard R/V Atlantis at the coast of California indicate that BC emitted from large to medium-sized urban centers (dominated by fossil fuel emissions) does not exhibit a substantial absorption enhancement when internally mixed with non-BC material suggesting that the warming by BC may be overestimated in climate models. The climate benefits of BC mitigation would similarly be overestimated.

Division of Atmospheric Sciences at Department of Physics directly contributed to this work by measuring the mixing state of the ambient aerosol particles with the Hygroscopicity Volatility Tandem Differential Mobility Analyzer (HVTDMA). The instrument was developed at the Department of Physics.

Reference:

Cappa, C.D., Onasch, T.B., Massoli, P., Worsnop, D.R., Bates, T.S., Cross, E.S., Davidovits, P., Hakala, J., Hayden, K., Jobson, B.T., Kolesar, K.R., Lack, D.A., Lerner, B.M., Li, S.-M., Mellon, D., Nuaaman, I., Olfert, J.S., Petäjä, T., Quinn, P.K., Song, C., Subramanian, R., Williams, E.J. and Zaveri, R.A. (2012) Radiative absorption enhancements due to the mixing state of atmospheric black carbon, Science 337, 1078-1081.

A recipe to measure formation of atmospheric aerosol particles

The formation of new atmospheric aerosol particles and their subsequent growth have been observed frequently at various locations all over the world. These particles contribute to the global aerosol number budget and affect the concentrations of cloud condensation nuclei and thus the global climate. Based on our recent advances in measurement and data analysis techniques together with long-term observations and intensive measurement campaigns world-wide, we describe the present instrumentation, best practices and other tools used to investigate atmospheric nucleation. This work is a comprehensive protocol required to assess the atmospheric aerosol formation.

Reference:

Kulmala, M., Petäjä, T., Nieminen, T., Sipilä, M., Manninen, H.E., Lehtipalo, K., Dal Maso, M., Aalto, P.P., Junninen, H., Paasonen, P., Riipinen, I., Lehtinen, K.E.J., Laaksonen, A. and Kerminen, V-M. (2012) Measurement of the nucleation of atmospheric aerosol particles, Nature Protocols 7, 1651-1667, doi:10.1038/nprot.2012.091.