I would like to eat crow
Hello all,
I posted the reply stating that Fog is cloud that touches the ground. That's what my Meteorology instructor told me and he worked for the Bureau of Meteorology here in Australia... so naturally I took his word literally. And the definition of low level cloud is cloud that occurs from ground level to 2500m, then mid-level and high level cloud.
But I would like to add the following, which may make my original post inaccurate and could open a can of worms... but here goes.
I said that Fog was stratiform cloud that touches the ground. I would like to correct my statement and say that cloud, according the Bureau, and aviation meteorology books, is formed when a lifting mechanism causes the air to become saturated. The normal lifting mechanisms are orographic, frontal, convective or mechanical.
Fog, on the other hand, can be caused by conduction, radiation or advection.
So let me correct myself and say that cloud is the formation of visible moisture and the product of a lifting mechanism and fog is the formation of visible moisture and the product of cooling without there necessarily being a lifting mechanism.
Fog, by definition, has visibility less than 1000m and mist has visiblity greater than 1000m.
So that's the way I interpret it and what I guess is one of the reasons why fog is treated separately to cloud in forecasts and reports.
I welcome any input if I'm incorrect.