Project status

BRIEF SUMMARY OF THE ACHIEVEMENTS OF THE PROJECT(1st of January 2009 - 30th of June 2011):

Atmospheric aerosols through their formation of haze and clouds mask the true rate of greenhouse gas induced global warming. Due to this crucial role of aerosol in the climate system improved aerosol parameterizations is perhaps the single most important challenge of the next generation climate models. This can only be based on superior understanding on the processes of new aerosol formation from gaseous vapours, aerosol growth and removal in the atmosphere. Especially little is known about the detailed molecular-scale processes behind the observed particle formation events. ATM-NUCLE project aims to quantify the mechanisms for atmospheric new particle formation and the growth process and, finally, attain holistic understanding how aerosol formation processes affect the climate system.

The first results of ATMNUCLE are mostly based on our new measurement innovations for detecting charged and neutral particles and clusters down to 1.1 x 10−9 m in diameter. Before these results, it was not possible to measure neutral particles and clusters in 1.1-2.0 nm size range. New measurements both in laboratory and field has lead to deeper understanding on the overall role of sulphuric acid in atmospheric nucleation and neutral sulphuric acid in cluster formation.

 In field conditions we have been able characterize with new instrumentations (particle size magnified (PSM) and (Atmospheric Pressure interface Time-of-Flight Mass Spectrometer (APi-ToF) the first steps of ion induced nucleation and show that sulphuric acid and ammonia (and/or amines) are involved in the formation of the small clusters during the nucleation. In those studies it was also found that certain volatile organic vapours, synthesized in photosynthetic processes, have a significant role in atmospheric new particle formation. Particularly, biogenic secondary organics are dominating the growth of freshly formed nanoparticles to cloud condensation nuclei (CCN) sizes. We have also analyzed long-term measurements from the SMEAR (Station for Measuring Forest-Ecosystem Atmosphere Relations) super site in Finland and showed that the CCN concentrations increase  within the next 24 h by 70-110 % after days when the new aerosol particle formation are detected. Given the high number of days when new particle formation takes place, these observations can be significant as indicated by the climate modellers. To complete understanding of atmospheric nucleation we have also used theoretical methods (quantum chemistry calculations) to provide information on neutral cluster formation. Our latest results points to amines, more specifically to dimethylamine (DMA) as the best candidates to play a key role in atmospheric nucleation.

We have started to integrate new knowledge on atmospheric nucleation from nano and local scales up to regional and global scales. Â New nucleation and biogenic aerosols schemes have been implemented into a global aerosol-climate model ECHAM5-HAM. Although the representation of biogenic organics in new ECHAM5-HAM model is simple, it captures the dominant role of volatile organic compounds (VOCs) in the growth of newly formed particles into CCN sizes. Â While representation of organic aerosols still needs to be substantially improved in global aerosol models, we have begun to study how future changes in atmospheric oxidation capacity might affect the properties of clouds. First results show that using a combination of global and regional aerosol and chemistry models, the possible future increases in atmospheric methane levels can lead to a strong positive aerosol forcing due to subsequent decrease in atmospheric oxidant levels.

ATM-NUCLE Science Plan