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Atmospheric Sciences

The main research activities are (i) aerosol and environmental physics, (ii) micrometeorology and forest-atmosphere relations (iii) dynamical and physical meteorology.

The core of the research is the understanding of energy, mass and momentum transfer and phase transitions. Theoretical, modeling and experimental studies of nucleation, condensation/evaporation and atmospheric aerosol dynamics have continued in 2010. Studies of deposition and fluxes of atmospheric gases, cloud microphysics, atmospheric radiation, mesoscale meteorology, and climate and radar meteorology were performed.

The division operates together with 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. The division is also in charge to establish national and European Integrated Carbon Observation System (ICOS).

The division has co-ordinated and participated in several international projects. The Division hosted International Aerosol Conference (over 1400 participants) and 15 smaller national and international workshops and conferences in 2010. The division organized also more than 10 intensive measurement campaigns in Finland and abroad, most important ones being CLOUD (Cosmics Leaving OUtdoor Droplets at CERN) and HUMPPA (Hyytiälä United Measurements of Photochemistry and Particles in AIR with MPI Mainz).

Highlights of research

Many terrestrial biogeochemical feedbacks
tend to warm the atmosphere

The terrestrial biosphere is a key regulator of atmospheric chemistry and climate. Although interactions between the carbon cycle and climate have been a central focus, other biogeochemical feedbacks could be as important in modulating future climate change. We studied the radiative forcing from terrestrial biogeochemistry feedbacks in response to anthropogenic atmospheric and climate changes. The nitrogen limitation to carbon uptake, peatlands including methane and permafrost areas, effects of ozone and fires were considered. Overall, the associated feedbacks tend to warm the atmosphere and substantially reduce and potentially even eliminate the cooling effect owing to carbon dioxide fertilization of the terrestrial biota. However, there are large uncertainties in the magnitude of individual estimates and in accounting for synergies between these effects.   

Arneth, A., S.P. Harrison, S. Zaehle, K. Tsigaridis, S. Menon, P.J. Bartlein, J. Feichter, A. Korhola, M. Kulmala, D. O’Donnell, G. Schurgers, S. Sorvari and T. Vesala: Terrestrial biogeochemical feedbacks in the climate system. Nature Geoscience 3, 525-532, 2010.

Atmospheric Nucleation

New particle formation in the atmosphere produces ca 50% of atmospheric aerosol particles.  Sipilä et al. (2010) showed, as a result of laboratory experiments conducted in collaboration with Leibniz Institute of Tropospheric Research, Leipzig and Finnish Meteorological Institute, that sulfuric acid is the key compound in atmospheric boundary layer nucleation. Observation was made possible by utilization of particle counters that can detect molecular clusters containing only few molecules of sulfuric acid. Those particle counters have recently been developed at the Division of Atmospheric Sciences. In the work of Sipilä et al. the reason for the failure of previous experiments to reproduce atmospheric observations was shown to result from the slow growth rates of small clusters and size sensitive counting efficiency of the particle counters applied for detecting the nucleated particles.

Sipilä M., Berndt T., Petäjä, Brus D., Vanhanen J., Stratmann F., Patokoski J., Mauldin IIIR.L., Hyvärinen A.-P., Lihavainen H. and Kulmala M.: The Role of Sulphuric Acid in Atmospheric Nucleation, Science, 327, 1243-1246, 2010

Kuvio 7.

Sipilä et al. (2010) applied high sensitivity particle detectors developed at Department of Physics to study particle formation from sulfuric acid vapor. They were first to reproduce atmospheric observations on the relation between sulfuric acid concentration and the formation rate of new particles.