Speaker
Description
Fog reduces visibility, causing delays in transportation by land, sea and air. It is also a safety hazard that results in accidents and sometimes even death. Like cloud droplets, fog droplets form on cloud condensation nuclei, existing aerosol particles in the atmosphere that have the ability to activate into droplets. As such, fog droplets provide a unique, in situ method of studying the process of aerosol activation. The interactions between aerosols and water vapour can determine the formation and persistence of fog, which makes fog forecasting challenging. Current parameterizations within models suffer notably from unresolved microphysical problems such as neglecting droplet concentration, which leads to large errors in droplet density predictions and therefore visibility. This study presents results from fog studies conducted on the eastern coast of Canada in Nova Scotia. Observations of aerosol size distributions and chemical composition were conducted using a ground-based counter flow virtual impactor, which allowed the droplet residuals to be measured directly. Fog droplet size distributions, visibility and other meteorological variables were also measured at the same time. Aerosol and droplet microphysical parameters will be presented including the influence of air mass history. Preliminary results show that aerosol growth may be contributing to the dissipation of fog under some conditions, suggesting that despite the importance of atmospheric dynamics on fog formation and dissipation, aerosols can also play an important role in the life cycle of fog.
