Fog, which can be defined as a cloud at ground level with surface visibility less than 1 km, can cause major disruption to road, aviation and marine transport, with associated economic losses comparable to both winter storms and hurricanes. Fog is dependent on a number of small-scale physical processes (radiative, dynamical, thermodynamical, microphysical), which results in an air mass become saturated and fog forming. A process that is still misunderstood is the role of microphysics and in particular, the importance of aerosol-fog interactions within the fog life cycle. Aerosols are important for fog, as they form the substrate on which water condenses and fog droplets form. The number of formed droplets then determine the life span of the fog layer, as well as its optical thickness. However, there is an associated uncertainty with aerosol-fog interactions, making the modelling and forecasting of fog difficult. Although research into radiation fog has spanned the last 100 years, recognition of aerosols is more recent.
The aim of this project is to investigate the importance of aerosol-fog interactions during the nocturnal stages of radiation fog. For this work, a range of simulations will be performed based on different aerosol properties, and then compared to an optically thin fog layer based in the UK from the recent Local And Non-local Fog EXperiment (LANFEX) field campaign. Simulations are undertaken with the Met Office NERC Cloud model (MONC), coupled with the Cloud AeroSol Interactive Microphysics (CASIM) scheme. MONC is a newly developed large eddy simulation model and has been designed for research and development of parameterisations for the forecast model. CASIM has been developed as a long term replacement for the Met Office UM microphysics scheme, where it has the ability to investigate aerosol-cloud interactions in a range of different environments. A number of key questions have been set out, which include:
- What is the importance in the aerosol number and size during the evolution of fog?
- Could the physics of fog droplet formation and in particular, aerosol activation be better represented?
- How does the change in microphysics influence the internal dynamical structures of the fog layer?
- Is representing aerosol removal a requirement for modelling nocturnal fog?
- Computational Fluid Dynamics
- Cloud Microphysics
- Stable Boundary Layers
- BSc Mathematics, King's College London
Research groups and institutes
- Institute for Climate and Atmospheric Science