The doctoral dissertation in the field of Aerosol 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 examines how atmospheric aerosols influence the Earth’s climate, with a focus on improving how their complex interactions with clouds and radiation are represented in climate models. Aerosols, especially those formed from organic vapours, play a key role in cloud formation and radiative balance, but their properties and effects are still highly uncertain.
By combining advanced atmospheric modelling, satellite observations, and machine learning, I investigated how changes in aerosol characteristics and emission sources impact cloud microphysics and climate-relevant parameters. This research contributes to reducing major uncertainties in climate projections, supporting more accurate assessments of human and natural influences on climate, and helping to inform policy on emissions and land use.
What are the key findings or observations of your doctoral research?
My research shows that assumptions about the volatility of organic vapours significantly influence how aerosols form and interact with clouds, which in turn affects climate-relevant properties such as cloud droplet concentration and radiative forcing. Even modest changes in these assumptions can lead to substantial differences in the predicted amount of secondary organic aerosols and their climatic effects. Different ways of using forest biomass, for example, for energy or pulp production, can also result in very different impacts on climate due to changes in aerosol emissions.
A key highlight of this research is the use of machine learning to more accurately estimate how aerosols affect clouds based on satellite observations and multiple modelling approaches. This method offers a more reliable alternative to traditional regression techniques, especially under complex atmospheric conditions. These findings advance our understanding of aerosol–cloud–climate interactions and support the development of more accurate climate models and informed environmental policies.
How can the results of your doctoral research be utilised in practice?
The results can be used to improve the representation of aerosols in global and regional climate models, leading to more accurate climate projections. This is particularly relevant for scientists and policymakers working on climate change mitigation and air quality management. The findings related to forest biomass use can help guide sustainable land-use and energy strategies by revealing how different practices affect climate through aerosol emissions.
Additionally, the machine learning approach utilized in this research offers a practical tool for better interpreting satellite observations of aerosol–cloud interactions, which can support research institutes in climate monitoring and model evaluation.
What are the key research methods and materials used in your doctoral research?
The research combined a range of modelling approaches, satellite observations, and statistical techniques to investigate how aerosols influence clouds and climate. Process-level simulations were carried out using the MCOLNAG model to examine the formation of secondary organic aerosols under different volatility conditions. Large-scale effects were studied using the global aerosol-climate model ECHAM-HAMMOZ coupled with the aerosol microphysics model SALSA. A cloud parcel model was used to simulate cloud droplet activation under varying aerosol and meteorological conditions, and a radiative transfer model (libRadtran) helped estimate satellite-derived cloud-base updraft velocities. Satellite data from MODIS were used to retrieve cloud properties, which were then analyzed using both traditional regression methods and machine learning to better understand aerosol–cloud interactions. This multi-scale and multi-method framework enabled a comprehensive analysis of the physical processes and climate implications of aerosol behaviour.
The doctoral dissertation of Muhammed Irfan, MSc, entitled Modelling aerosol effects on climate: From organic volatiles to cloud interactions and radiative forcing will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus. The opponent will be Senior Lecturer, Ph.D. Pontus Roldin, Lund University, Sweden, and the custos will be Professor, Harri Kokkola, 91. Language of the public defence is English.
For more information, please contact:
Muhammed Irfan, mirfan@uef.fi, tel. +358 504 757 502
- Public examination
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