Project description - Interaction between boreal forests and the atmospheric aerosol
Research Leader: Prof. Veli-Matti Kerminen, Finnish Meteorological Institute, Sahaajankatu 20 E, 00880 Helsinki, tel. +358 - (0)9-1929 5501, 050-342 7380, fax. +358 - (0)9-1929 5403,
veli-matti.kerminen(at)fmi.fi, www.fmi.fi
Abstract
Boreal forests constitute one of the largest vegetation zones in the world and cover a major fraction of the land surface area in Scandinavia and Russia. It has been demonstrated that boreal forests are an important natural source of small aerosol particles into the atmosphere, having a potential to influence the global climate and human health.The primary objective of this project is to provide, for the first time and in a large geographical scale, a quantitative understanding on how the boreal forest zone interacts with the atmospheric aerosol system and ultimately climate. Within this framework, we aim to address the following more specific questions: 1) what are the physical and chemical properties of atmospheric aerosols over the Russia and how they vary temporally and spatially compared with similar observations in Finland?, 2) what are the primary sources of anthropogenic aerosols over Russia and how they are transported to the boreal forest zone?, 3) what are the emissions of natural aerosol particles from the boreal forest zone? and 4) what is the radiative forcing of aerosols emitted by boreal forests?
In order to estimate the various influences of aerosols emitted by boreal forests, detailed measurement data from large geographical areas are needed. In the proposed project such data will be provided by conducting a measurement campaign in Russia, which includes real-time measurement of aerosol physical and chemical properties and collection of aerosol samples for subsequent chemical analysis. The results will be compared to similar measurements that have been performed continuously at the SMEAR II station in Hyytiälä, central Finland, during the last few years. The investigation will be completed by comprehensive data analysis and modelling activities with regard of the formation and growth of forest aerosols and their climatic forcing.
Background and objectives
Boreal forests constitute one of the largest vegetation zones in the world, covering more than 17 million km2 and accounting for about 33% of the overall forest area (Matthews, 2001). A major fraction of the land surface area and great majority of forests in Scandinavia and Russia belong this zone. Boreal forests can therefore be considered extremely important from economical, ecological and health point of view for the people living in these countries.
Boreal forests interact with the atmosphere by acting as a sink carbon dioxide and many atmospheric pollutants (e.g. Betts, 2000), and by emitting volatile organic compounds participating in atmospheric chemistry (e.g. Simpson et al., 1999; Lindfors et al., 2000). More recently, it has been demonstrated that boreal forests are an important natural source of small aerosol particles into the atmosphere (Yu et al., 1999; Kulmala et al., 2001). Once grown into larger sizes, these aerosol particles may act as cloud condensation nuclei and modify many cloud properties (Kurten et al., 2003). In addition to their climatic effects, forest aerosols might influence human health due to their ability of penetrate deep into a human respiratory system.
A number of questions concerning the interaction between the boreal forests and atmospheric aerosol system remain. Among these are the following: 1) what is the global source strength of natural aerosols from the boreal forests, 2) how susceptible are the boreal forests, and especially their emissions, to various anthropogenic pollutants such as acidic aerosols, and 3) what is the climatic forcing of natural aerosols emitted by the boreal forests? To address these questions, detailed aerosol measurement data from large geographical areas are needed. In this project, such data will be provided by conducting an extensive measurement campaign over Russia using a mobile carriage laboratory that is coupled to passenger trains. The results will be compared to similar measurements that have been performed continuously at the SMEAR II station in Hyytiälä, central Finland, during the last few years. The investigation will be completed by comprehensive data analysis and modelling activities.
Our overall objective in this project is to provide, for the first time and in a large geographical scale, a quantitative understanding on how the boreal forest zone interacts with the atmospheric aerosol system and ultimately climate. Within this framework, we aim to address the following more specific questions:
- what are the physical and chemical properties of atmospheric aerosols over the Russia and how they vary temporally and spatially compared with similar observations in Finland?
- what are the primary sources of anthropogenic aerosols over Russia and how they are transported to the boreal forest zone?
- what are the emissions of natural aerosol particles from the boreal forest zone?
- what is the radiative forcing of aerosols emitted by boreal forests?
The working hypothesis of the proposed project are that 1) the boreal forest zone is a globally significant source of natural aerosol particles into the atmosphere, and that 2) these aerosols have a radiative cooling effect that must be taken into account in regional and possibly also in global climate change investigations.
Research methods
The proposed project includes detailed aerosol characterization measurements (real-time measurement of aerosol physical and chemical properties, collection of aerosol samples), chemical analysis of aerosol samples (concentrations of inorganic and organic ions in different particle size ranges, black carbon concentration), data analysis (aerosol measurement data, air mass transport in Russia) and modelling activities (formation and growth of forest aerosols and their climatic forcing).
Measurement locations
Most of the measurements will be conducted in Russia within a so-called TROICA-expedition. The purpose of TROICA is to monitor atmospheric pollutants over Russian region, which will be done using a mobile carriage laboratory that is coupled to passenger trains moving by electrified railroads. Since 1995, the same laboratory has been used successfully for monitoring the distribution of gaseous pollutants over the Eurasian continent along the Moscow-Khabarovsk-Moscow route of the Trans-Siberian Railroad. In TROICA, the carriage laboratory will be equipped with additional measurement instrumentation in order to monitor and sample atmospheric aerosol particles. The results from aerosol measurements in Russia will be compared to similar measurements that have been performed continuously at the SMEAR II station in Hyytiälä, central Finland, during the last few years.
Measurements and instrumentation
During the TROICA-expedition, our group is responsible for a detailed physical and chemical characterization of aerosol particles. This will be done using the following set of instruments:
- Differential Mobility Size Spectrometer (DMPS)
- Ion spectrometer
- Hygroscopic Tandem Diffusion Mobility Analyser (HTDMA)
- Aethalometer
- Small deposit low-pressure impactor (SDI)
- Virtual impactor (VI)
The first four of these instruments (the DMPS, Ion Spectrometer, HTDMA and Aethalometer) provide semi-continuous data (typical time resolution of a few minutes), whereas typical sampling times of the SDI and VI are in the range 12-48 hours. Our group has a wide experience in using all these instruments under different field conditions.
Chemical analysis
All the chemical analyses of the samples will be performed in the FMI aerosol laboratory. The SDI samples will be analysed for inorganic ions and organic acids. The VI samples are used to determine the concentrations of inorganic ions, organic acids, trace elements and organic carbon.
Data analysis
A data bank will be constructed which contains all the relevant data associated with measurements over Russia. Our group provides the detailed aerosol data (concentrations, number size distributions, size-segregated chemical composition, particle formation and growth rates) and data on air mass transport from different source areas to the measurement site based on trajectory calculations. Other data (concentrations of gaseous pollutants, basic meteorological data) are obtained from other partners participating the project.
Modelling
The modelling work concentrates on forest aerosols and includes two tasks: 1) modelling the formation and growth of aerosols resulting from emissions by boreal forests, and 2) calculating the radiative forcing associated with forests aerosols.
The first of these tasks will be performed with state-of-the-art aerosol dynamical models that have been developed during the recent years in our institutes (Kerminen et al., 2000; Lehtinen and Kulmala, 2003; Anttila and Kerminen, 2003; Korhonen et al., 2004). Further development of these models during the coming years is made within other research projects.
The second task involves calculating both direct and indirect forcing caused by boreal forest aerosols. A preliminary estimation of the indirect forcing has already made for aerosols emitted by Finnish boreal forests (Kurten et al., 2003). The purpose of this project is to reduce the large uncertainty range associate with this forcing estimate and to expand it to cover the large boreal forest zone over Russia. In doing this we will use the large aerosol data base obtained from the TROICA-expedition and develop the analytical and modelling tools needed in forcing calculations.
Research group
The core of the research group consists of two teams, one from Finnish Meteorological Institute, Air Quality Research (FMI), and the other from University of Helsinki, Department of Physical Sciences, Division of Atmospheric Sciences (UHEL).
Finnish Meteorological Institute team
Veli-Matti Kerminen, research professor
* general coordination, interpretation of field measurements and aerosol modelling
Risto Hillamo, Ph.D., docent
* coordinator of size-segregated chemical aerosol measurements
Aki Virkkula, Ph.D.
* aerosol optical measurements, overall data analysis
Kimmo Teinilä, M.Sc., Ph.D. student
* sampling and chemical analysis of size-segregated aerosol samples
University of Helsinki team
Markku Kulmala, professor
* coordinator of aerosol physical measurements, aerosol modelling
Kari Lehtinen, Ph.D., docent
* coordinator of modelling activities
Tuukka Petäjä, M.Sc. at the beginning of 2004, Ph.D student during the project
* physical aerosol measurements, data analysis
Miikka Dal Maso, M.Sc. by the end of 2003, Ph.D student during the project
* analysis of aerosol measurement and air mass transport data
Russian teams participating the project
The Federal State Unitary Enterprise All-Russian Railway Research Institute (VNIIZhT)
* setting up the mobile carriage laboratory with the basic electro-technical equipment; arrangements concerning the installation of instruments and ancillary equipment
A. M. Obukhow Institute of Atmospheric Physics RAS (IAP)
* integrated automatic monitoring of atmospheric gaseous and aerosol pollutants and parameters of the atmospheric state during the mobile laboratory measurements
The Federal State Unitary Enterprise Karpov Institute of Physical Chemistry (KIPC).
* additional aerosol characterization measurements in the mobile carriage laboratory (aerosol scattering, concentrations and size distribution of large aerosols)
Other teams participating the project
Max-Plank Institute for Chemistry, Atmospheric Chemistry Department
* monitoring of gaseous pollutants in the mobile carriage laboratory, climate simulations
Climate Monitoring and Diagnostic Laboratory, National Oceanic and Atmospheric Administrations (CMDL/NOAA)
* monitoring of long-living gaseous pollutants and analysing their principal mechanisms
Expected results
The main results from the proposed project include 1) detailed characterisation of aerosol physical and chemical properties over boreal forests in Russia and Finland, and 2) quantitative understanding on how the boreal forests interact with the atmospheric aerosol system. Due to our long experience in this research area, we have further a unique possibility to find out the significance and effects of boreal forests on regional and global climate (radiative cooling by aerosols emitted by boreal forests) and human health.
The research results obtained from the project will be published in peer-reviewed scientific journals (e.g. Nature, Science, Journal of Geophysical Research, Atmospheric Environment, Journal of Aerosol Science). The results will also be presented in international and national conferences (e.g. European Aerosol Conference, Annual Meeting of the American Association for Aerosol Research, Annual Meeting of the European Geophysical Union) and workshops.
Since the research will be conducted in close collaboration with Russian partners, realisation of the project would strengthen their contacts with foreign scientific institutes, widening the volume of information on observance of the obligations taken by Russia in accordance with different international agreements on the environmental protection.
References
Anttila T. and Kerminen V.-M. (2003) Condensational growth of atmospheric nuclei by organic vapours. J. Aerosol Sci. 34, 41-61.
Betts R. A. (2000) Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. Nature 408, 187-190.
Kerminen V.-M., Virkkula A., Hillamo R., Wexler A. S. and Kulmala M. (2000) Secondary organics and atmospheric CCN production. J. Geophys. Res. 105, 9255-9264.
Korhonen H., Lehtinen K. E. J. and Kulmala M. (2004) Multicomponent aerosol dynamics model UHMA: model development and validation. Atmos. Chem. Phys. Discuss. 4, 471-506, 2004
Kulmala M., Hämeri K., Aalto P., Mäkelä J. M., Pirjola L., Nilsson E. D., Bozorius G., Rannik U., Dal Maso M., Seidl W., Hoffman T., Janson R., Hansson H.-C., Viisanen Y., Laaksonen A. and O=Dowd C. D. (2001) Overview of the international project on biogenic aerosol formation in boreal forest. Tellus 53B, 324-343.
Kurtén T., Kulmala M., Dal Maso M., Suni T., Reissell A., Vehkamäki H., Hari P., Laaksonen A., Viisanen Y. and Vesala T. (2003) Estimation of different forest-related contributions to the radiative balance using observations in southern Finland. Boreal Environ. Res. 8, 275-285.
Lehtinen, K. E. J. and Kulmala, M. (2003) A model for particle formation and growth in the atmosphere with molecular resolution in size. Atmos. Chem. Phys. 3, 251?257.
Lindfors V., Laurila T., Hakola H., Steinbrecher R. and Rinne J. (2000) Modeling speciated terpenoid emissions from the European boreal forest. Atmos. Environ. 34, 4983-4996.
Matthews E. (2001) Understanding the FRA 2000, World Resource Institute Briefing no 1, World Resource Institute.
Simpson D., Winiwarter W., Borjesson G., Ginderby S., Ferreiro A., Guenther A., Hewitt C. N., Janson R., Khalil M. A. K., Owen S., Pierce T. E., Puxbaum H., Shearer M., Steinbrecher R., Tarrason L., and Öquist M. G. (1999) Inventorying emission from nature in Europe. J. Geophys. Res. 104, 8113-8152.
Yu J., Griffin R. J., Cocker D. R. III, Flagan R. C. and Seinfeld J. H. (1999) Observation of gaseous and particulate products of monoterpene oxidation in forest atmospheres. Geophys. Res. Lett. 26, 1145-1148.