That is also why it takes just a slight breeze to get thick
fog. No wind at all, no fog, stronger winds push the cloud
bases up a few hundred feet and IFR becomes possible when
ILS minimums are reached.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Icebound" wrote in
message ...
|
| "Jim Macklin" wrote
in message
| news:%mqNf.107786$QW2.7653@dukeread08...
| It causes some vertical motion which stirs the air a
little,
| casing the fog to form.
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|
|
|
|
| Yes!
|
| The very coldest air at that time of morning is right at
the surface of the
| earth. As it starts to mix with air above it, it cools a
whole layer of 50
| or a hundred feet or so, instead of just the thin surface
layer. If the
| average moisture content through that layer is such that
the cooling drops
| the temperature down to the average dew-point, bingo.
|
| If you watch weather reports carefully, you will find that
in those
| clear-morning situations, the lowest temperature occurs
*after* sunrise,
| when you would have expected that warming is started. But
when this mixing
| starts, that coldest air at the surface (as part of the
slight turbulence)
| reaches up to the 1 metre level where the "official"
thermometers are kept.
|
| If you check a weather observing site which observes
"grass" temperatures,
| such as an experimental farm or the like, you will see
just how great this
| temperature difference between the grass level and the
official 1 meter
| level can be at sunrise... exceeding 5 degrees Celsius in
clear-sky cases.
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