Marine fog and its dissipation over warm water

Abstract

A long aircraft flight in fog at altitude 60 m was conducted on 25 September 1981, due west from San Francisco, California, until clear air was reached. The fog began near the coast and the air remained foggy until the boundary with the warmer seawater. This sea surface temperature transition provides a sudden 3° to 4°C temperature increase between two regions of relative uniform surface temperature water. In fog the random vertical motion (turbulence) is extremely low, the foggy air essentially being still, but on encountering warmer water convection starts, the air becomes turbulent, and rapid drying results due to the now warmer cloud parcels penetrating the inversion so the drier overlying air is mixed down. The fog average drop diameters are close to 11 μm, but the concentration ranges from 10 to 250 drops mg-1. This corresponds to slow entity-type entrainment mixing. -from Authors