Modelling Marine Boundary-Layer Fog Development over Changes in Surface Conditions

Peter Taylor’s research group have a new 6-month NSERC-ENGAGE grant (Started Oct. 1, 2016) with AMEC Foster Wheeler to study fog over the Grand Banks. Dr. Wensong Weng and Adjunct Professor George Isaac will be involved. The proposal summary is:

“Marine fog over the Grand Banks offshore from Newfoundland and in other marine areas is a significant problem for many activities, but especially for helicopter landings on oil rigs. The fog may extend upwards from the sea surface to heights of the order  of 100m to 300m, and it is important to understand the processes and conditions that determine the evolution, opacity, and depth of the fog layer. In many instances, fog formation is associated with winds blowing air over changes in surface temperature.

These advective fogs have some similarities with the radiation fogs that are common over land, but have added complications associated with internal boundary layer development. There has been considerable activity in the development of 1-D (horizontally homogeneous) time-dependent fog models, including detailed treatment of micro-physical and radiative processes and turbulent transports. There has been rather less activity related to advection fogs, but papers by Nakanishi and Niino (2006) and by Barker (1976) provide a good starting point for us.

Dr. Taylor’s group at York University has undertaken extensive research on atmospheric boundary-layer models, including studies of flow over changes in surface roughness, temperature and humidity, taking account of the impacts of stratification on turbulence via Monin-Obukhov similarity theory. They have also modeled blowing dust and blowing snow with multiple size bins, sublimation and settling, plus visibility issues, which will provide the basis for the development of a superior boundary-layer fog model. The initial research plan will be to adapt our models of turbulent atmospheric (planetary) boundary-layer over changes in surface conditions to deal with situations where spatial variations in water surface temperature lead to situations where water vapor can condense and form fog. Details of the evolution of the fog droplet size distribution and radiative and visibility impacts will be added, and variations with wind speed and the horizontal rates of change will be investigated. On a longer term basis, we will seek ways to combine these findings with weather forecast models in order to improve practical forecasting of fog occurrence, depth and intensity.”

by Dr. Peter Taylor