The doctoral dissertation in the field of Applied Physics will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus.
What is the topic of your doctoral research? Why is it important to study the topic?
My doctoral research investigates how aerosols emitted from wildfires or biomass burning transform in the atmosphere and how these changes affect their ability to form cloud droplets. The aim was to improve our understanding of fire aerosols – from their emissions at the source to their effects on cloud properties after several days of atmospheric aging – through laboratory experiments and field measurements. Due to global warming and extreme heatwaves, wildfires have become more severe and frequent in recent years and are expected to increase significantly in the near future.
Fires release large amounts of aerosol particles into the atmosphere, affecting air quality, climate, and cloud formation. Once emitted, these particles undergo physical and chemical changes that can affect their ability to interact with clouds. Therefore, it is important to understand these processes and improve their representation in climate models to enable more accurate climate predictions.
What are the key findings or observations of your doctoral research?
The work consists of three studies that investigated the different stages of fire aerosols through a combination of laboratory experiments and field measurements. Laboratory experiments investigated the physical and chemical properties of fresh fire aerosols from the open burning of three different biomass fuels from South African Savannah grasslands and Finnish boreal forests and examined how different burning conditions and aging processes affect the evolution and secondary organic aerosol (SOA) formation potential of open fires. The results demonstrated that both daytime and nighttime aging produced a similar and moderate increase in aerosol mass concentration, providing new insights into the atmospheric evolution of fire aerosols.
Field measurements demonstrated that fire emissions from southeastern Europe can transport over large distances in the atmosphere and have a significant impact on the aerosol properties at two relatively clean high-latitude locations: Finland and even the high Arctic. Both locations experienced a substantial increase in aerosol number and mass concentrations as well as cloud droplet number concentrations (CDNC) during long-range transported fire events. This huge increase in CDNC can increase cloud albedo and alter cloud coverage and lifetime. These findings emphasize the large impact of fires on aerosol and cloud properties across local to regional scales.
How can the results of your doctoral research be utilised in practice?
The results from this research provide valuable data for improving the representation of fire aerosols in emission inventories and their evolution in atmospheric transport models as well as global climate models. These improvements can help reduce uncertainties in simulations and contribute to more accurate predictions of the impacts of wildfires on air quality, clouds, and climate.
What are the key research methods and materials used in your doctoral research?
Laboratory experiments of my doctoral research were carried out in the ILMARI laboratory facility (https://sites.uef.fi/ilmari/) at the University of Eastern Finland, where biomass samples were burned under controlled conditions and the emitted aerosols were aged under daytime and nighttime oxidation conditions in an atmospheric simulation chamber. Field measurements in this research work were carried out at the SMEAR-IV measurement station (https://www.atm.helsinki.fi/smear/smear-iv/) located on top of Puijo Tower, Kuopio. The SMEAR-IV measurement station provides long-term observations of atmospheric aerosols, gases, and cloud droplet properties. This enabled the investigation of the effect of long-range transported fire air masses on aerosol and cloud properties in Finland. Finally, the aerosol physical and chemical properties were measured with a wide range of online and offline instruments within the Aerosol Physics Group at the University of Eastern Finland.
The doctoral dissertation of Snehitha Kommula, MSc, entitled From emissions to aerosol-cloud interactions: Evolution and cloud activation of fire aerosols will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus. The opponent will be Lecturer Zamin A. Kanji, ETH Zurich, Switzerland, and the custos will be Professor Annele Virtanen, University of Eastern Finland. Language of the public defence is English.
For further information, please contact:
Snehitha Kommula, [email protected], tel. +358 50 475 3989
