Examples of droplet size distribution and liquid water content in fog

Rapid visibility changes often threaten aviation safety and interrupt airport operations. And visibility changes caused by fog are difficult to forecast. Then fog droplet spectra and its profiles were observed to understand fog evolution. Under fog layers thinner than 130 m fog droplets smaller than 40¿m were important which were expected to be strongly influenced by condensation process for poor visibility. And under thicker fog layers, short visibility caused of larger droplets expected to be affected by coalescence process. Temporary improvement and degrading of visibility were strongly affected by downward transport of drier air parcels and settlement of fog droplets from upper denser fog layers. These vertical motions and droplets settlement played an important role to change visibility rapidly.