Is it colder at the approach end of the runway?

My dad drives along the south side of OKC to work every day and his OAT
in his car always goes a few degrees colder around the where the
extended centerline for the runways would intersect the road. Then it
goes right back up after he is through that area. He thinks this is
because the airplanes are descending from very cold air and bringing
down some of it with them. He has noted that this isn't always the case
but it often is. You would think most of the traffic would be landing
from the north since our winds are mostly from the south, but it seems
like I see a lot of traffic coming in from the south, maybe because it
is easier for the traffic from DFW to just come strait in.

Anyway, any one here think it is really the case that the planes are
causing the temperature to be lower on the approach end of the runway?
I guess if he monitored the ATIS frequency to find out which runway was
active when he drives by every day, he would have a better idea.


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Chris W wrote:
maybe because it
is easier for the traffic from DFW to just come strait in.

Make that "straight"
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Chris W writes:

My dad drives along the south side of OKC to work every day and his OAT
in his car always goes a few degrees colder around the where the
extended centerline for the runways would intersect the road. Then it
goes right back up after he is through that area. He thinks this is
because the airplanes are descending from very cold air and bringing
down some of it with them.

I would not have thought of that, but it's certainly plausible. Aircraft
produce a massive downwash of air behind them that (at least in theory) drifts
downward until it encounters the ground. In the case of aircraft very near
the surface (as during landing and take-off), it's entirely possible that they
might produce gentle downdrafts of colder air that reach the ground. I think
it would take fairly constant traffic using the runway to make a clear
difference, though.

It's a bit like the constant wind that one often feels by the side of a
highway or major city street, always in the direction of traffic. Moving
vehicles do displace a lot of air.

He has noted that this isn't always the case
but it often is. You would think most of the traffic would be landing
from the north since our winds are mostly from the south, but it seems
like I see a lot of traffic coming in from the south, maybe because it
is easier for the traffic from DFW to just come strait in.

Things like noise abatement and other concerns might obligate the airport to
work against the wind, at least if the wind speed is low enough (less than 10
knots or so).

Anyway, any one here think it is really the case that the planes are
causing the temperature to be lower on the approach end of the runway?

I think it's plausible.

Also, if the extended centerline is mostly open area (not buildings or roads),
that could make a difference as well. An open field is often colder than a
large building, because it absorbs solar energy less rapidly and retains it
less efficiently, and because it doesn't generate any heat of its own.

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Transpose mxsmanic and gmail to reach me by e-mail.

Mxsmanic wrote in
:

Chris W writes:

My dad drives along the south side of OKC to work every day and his
OAT in his car always goes a few degrees colder around the where the
extended centerline for the runways would intersect the road. Then
it goes right back up after he is through that area. He thinks this
is because the airplanes are descending from very cold air and
bringing down some of it with them.

I would not have thought of that, but it's certainly plausible.
Aircraft produce a massive downwash of air behind them that (at least
in theory) drifts downward until it encounters the ground. In the
case of aircraft very near the surface (as during landing and
take-off), it's entirely possible that they might produce gentle
downdrafts of colder air that reach the ground. I think it would take
fairly constant traffic using the runway to make a clear difference,
though.

It's a bit like the constant wind that one often feels by the side of
a highway or major city street, always in the direction of traffic.
Moving vehicles do displace a lot of air.

He has noted that this isn't always the case
but it often is. You would think most of the traffic would be
landing from the north since our winds are mostly from the south, but
it seems like I see a lot of traffic coming in from the south, maybe
because it is easier for the traffic from DFW to just come strait in.

Things like noise abatement and other concerns might obligate the
airport to work against the wind, at least if the wind speed is low
enough (less than 10 knots or so).

Anyway, any one here think it is really the case that the planes are
causing the temperature to be lower on the approach end of the
runway?

I think it's plausible.

You would, fjukktard.


Bertie

It is farther away from the built-up areas of the town, so
it is cooler. Houses make heat and so do factories.



|
| Chris W writes:
|
| My dad drives along the south side of OKC to work every
day and his
| OAT in his car always goes a few degrees colder around
the where the
| extended centerline for the runways would intersect the
road. Then
| it goes right back up after he is through that area.
He thinks this
| is because the airplanes are descending from very cold
air and
| bringing down some of it with them.
|
| I would not have thought of that, but it's certainly
plausible.
| Aircraft produce a massive downwash of air behind them
that (at least
| in theory) drifts downward until it encounters the
ground. In the
| case of aircraft very near the surface (as during
landing and
| take-off), it's entirely possible that they might
produce gentle
| downdrafts of colder air that reach the ground. I think
it would take
| fairly constant traffic using the runway to make a clear
difference,
| though.
|
| It's a bit like the constant wind that one often feels
by the side of
| a highway or major city street, always in the direction
of traffic.
| Moving vehicles do displace a lot of air.
|
| He has noted that this isn't always the case
| but it often is. You would think most of the traffic
would be
| landing from the north since our winds are mostly from
the south, but
| it seems like I see a lot of traffic coming in from the
south, maybe
| because it is easier for the traffic from DFW to just
come strait in.
|
| Things like noise abatement and other concerns might
obligate the
| airport to work against the wind, at least if the wind
speed is low
| enough (less than 10 knots or so).
|
| Anyway, any one here think it is really the case that
the planes are
| causing the temperature to be lower on the approach end
of the
| runway?
|
| I think it's plausible.

"Chris W" wrote in message
...
My dad drives along the south side of OKC to work every day and his OAT in
his car always goes a few degrees colder around the where the extended
centerline for the runways would intersect the road. Then it goes right
back up after he is through that area. He thinks this is because the
airplanes are descending from very cold air and bringing down some of it
with them. He has noted that this isn't always the case but it often is.
You would think most of the traffic would be landing from the north since
our winds are mostly from the south, but it seems like I see a lot of
traffic coming in from the south, maybe because it is easier for the
traffic from DFW to just come strait in.

Anyway, any one here think it is really the case that the planes are
causing the temperature to be lower on the approach end of the runway? I
guess if he monitored the ATIS frequency to find out which runway was
active when he drives by every day, he would have a better idea.


Which airport in OKC???

Maybe an active localizer/glideslope signal is affecting the thermometer
components. Air does not "stick" to an airframe enough to change the ambient
temperature of a given area no matter how small.

Marco

"Chris W" wrote in message
...
My dad drives along the south side of OKC to work every day and his OAT in
his car always goes a few degrees colder around the where the extended
centerline for the runways would intersect the road. Then it goes right
back up after he is through that area. He thinks this is because the
airplanes are descending from very cold air and bringing down some of it
with them. He has noted that this isn't always the case but it often is.
You would think most of the traffic would be landing from the north since
our winds are mostly from the south, but it seems like I see a lot of
traffic coming in from the south, maybe because it is easier for the
traffic from DFW to just come strait in.

Anyway, any one here think it is really the case that the planes are
causing the temperature to be lower on the approach end of the runway? I
guess if he monitored the ATIS frequency to find out which runway was
active when he drives by every day, he would have a better idea.

"Marco Leon" wrote in message
...

Air does not "stick" to an airframe enough to change the ambient temperature
of a given area no matter how small.

No, but everyone who has ever studied for their Private written knows that
the wake of an aircraft is accelerated down. So the passage of an aircraft
would cause a very temporary downward flow of air. Would the effect be enough
to noticeably change local temperatures? I doubt it; but who the hell am I?

On Apr 2, 5:33 pm, "Vaughn Simon"
wrote:
"Marco Leon" wrote in message

...

Air does not "stick" to an airframe enough to change the ambient temperature
of a given area no matter how small.

No, but everyone who has ever studied for their Private written knows that
the wake of an aircraft is accelerated down. So the passage of an aircraft
would cause a very temporary downward flow of air. Would the effect be enough
to noticeably change local temperatures? I doubt it; but who the hell am I?

What time of day does he go by? I could see the downwash mixing up
the air, and if there is a hot surface layer this could cool it.

As an example of downwash changing the temperature, I have heard
helicopter pilot stories about 'frost flights' at strawberry farms.
The task is to spend the night at the farm, and if the frost alarm
goes off in the wee hours you have to fly low over the fields in the
dark until the air is stirred up and the frost danger goes away. It
apparently is very effective in preventing frost damaged berries.

John Halpenny

On Apr 2, 9:18 pm, "John Halpenny" wrote:
On Apr 2, 5:33 pm, "Vaughn Simon"
wrote:

"Marco Leon" wrote in message

m...

Air does not "stick" to an airframe enough to change the ambient temperature
of a given area no matter how small.

No, but everyone who has ever studied for their Private written knows that
the wake of an aircraft is accelerated down. So the passage of an aircraft
would cause a very temporary downward flow of air. Would the effect be enough
to noticeably change local temperatures? I doubt it; but who the hell am I?

What time of day does he go by? I could see the downwash mixing up
the air, and if there is a hot surface layer this could cool it.

As an example of downwash changing the temperature, I have heard
helicopter pilot stories about 'frost flights' at strawberry farms.
The task is to spend the night at the farm, and if the frost alarm
goes off in the wee hours you have to fly low over the fields in the
dark until the air is stirred up and the frost danger goes away. It
apparently is very effective in preventing frost damaged berries.

John Halpenny


This has been done with fixed-wing airplanes, too. An airliner
on approach can't help but drive down air from a couple hundred feet
up. Problem with that, of course, is that the OP says his dad notices
this on the drive to work, presumably in the morning, and the air
aloft will be warmer rather than colder at that time. The nocturnal
inversion is still in play in the morning, before the surface heats
up. It's that warmer air the helicopters or other craft are driving
down at night into the orchards or vineyards or citrus groves.

Dan