Clouds have a profound effect on weather and climate due to their ability to reflect sunlight back to space and thermal radiation back to the Earth. At the core of each cloud droplet there is a so-called cloud condensation nucleus (CCN) that determines the properties of the droplet. Many different types of particles act as CCN, each with different properties. The goal of this project is to improve our quantitative understanding of the bi-directional links between chemistry, the CCN population and clouds in the marine boundary layer (MBL) as well as between these clouds and climate (via so-called indirect aerosol effects).

Over the last ~15 years the importance of reactive halogen chemistry for the oxidation capacity and particle composition and growth in the MBL has been shown in many field and modelling studies. In this time it has also become obvious that the role of gaseous and particulate organics in the MBL is very significant both for chemistry and the CCN population and hence clouds. 

This project will investigate both the chemical and microphysical processes in the MBL with the help of an established regional three-dimensional model (WRF/CHEM) that includes most relevant processes and can be run on various spatial scales. The focus regions will be the tropical North Atlantic (Cape Verde) as well as East Pacific. In both regions recent field campaigns have provided us with a wealth of data to compare the model results to.

The specific objectives of this studentship are:
• To quantify the impact of aerosol and cloud chemistry on the chemistry in the MBL.
• To quantify the impact of chemical processes on new particle formation and particle growth in the marine boundary layer (MBL).
• To quantify indirect radiative effects based on the outcomes of the previous objective.

This project is suitable for a student with a strong interest and ideally experience in atmospheric science and numerical modelling with a BSc or preferably a MSc in Meteorology, Atmospheric Sciences, Environmental Sciences, Physics, Mathematics, Chemistry or similar. The student will receive training in WRF-specific modelling and will acquire transferable skills, such as project planning, data analysis, effective collaboration, scientific writing, and oral communication, while participating in research of global significance.

O'Dowd, C. D. et al. (2004) Biogenically driven organic contribution to marine aerosol. Nature, 431:676 – 680

Bates, T. S., et al. (2012), Measurements of ocean derived aerosol off the coast of California, J. Geophys. Res., 117, D00V15, doi:10.1029/2012JD017588.

Kazil, J. et al. (2011), Modeling chemical and aerosol processes in the transition from closed to open cells during VOCALS-Rex, Atmos. Chem. Phys., 11, 7491-7514

von Glasow, R., et al. (2002), Modeling halogen chemistry in the marine boundary layer. 2. Interactions with sulfur and cloud-covered MBL, J. Geophys. Res., 107, 4323, doi: 10.1029/2001JD000943, 2002