How does sun heat the air?

[[email protected]]

The sun shines down through the atmosphere, hits things on the ground,
the things on the ground get hot, and then the hot things on the
ground heat the air?

Sun light passing through the air does not heat the air at all? Heats
the air some but not much?

If the air is transparent to solar energy, how is the air able to
pick up so much energy from hot objects on the ground?

Bill
6W

[Jim Logajan]

" > wrote:
> The sun shines down through the atmosphere, hits things on the ground,
> the things on the ground get hot, and then the hot things on the
> ground heat the air?
>
> Sun light passing through the air does not heat the air at all? Heats
> the air some but not much?
>
> If the air is transparent to solar energy, how is the air able to
> pick up so much energy from hot objects on the ground?

Try reading the content of this web page for some basic answers to all your
questions:

http://www.ucar.edu/learn/1_1_1.htm

[Eric Greenwell]

Jim Logajan wrote:
> " > wrote:
>> The sun shines down through the atmosphere, hits things on the ground,
>> the things on the ground get hot, and then the hot things on the
>> ground heat the air?
>>
>> Sun light passing through the air does not heat the air at all? Heats
>> the air some but not much?
>>
>> If the air is transparent to solar energy, how is the air able to
>> pick up so much energy from hot objects on the ground?
>
> Try reading the content of this web page for some basic answers to all your
> questions:
>
> http://www.ucar.edu/learn/1_1_1.htm

It's a good article by a good source, but robably more than he wants to
know, as it's not directly concerned with thermal production.

The thermals we like so much use air heated primarily by conduction from
the aforementioned hot objects, but I believe some "micro" (my term)
convection near the ground is important for making the warm layer near
the ground thicker than conduction alone would provide.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

[Tim Taylor]

On Oct 8, 8:52*pm, Eric Greenwell > wrote:
> Jim Logajan wrote:
> > " > wrote:
> >> The sun shines down through the atmosphere, hits things on the ground,
> >> the things on the ground get hot, and then the hot things on the
> >> ground heat the air?
>
> >> Sun light passing through the air does not heat the air at all? *Heats
> >> the air some but not much?
>
> >> If the air is transparent to solar energy, how is *the air able to
> >> pick up so much energy from hot objects on the ground?
>
> > Try reading the content of this web page for some basic answers to all your
> > questions:
>
> >http://www.ucar.edu/learn/1_1_1.htm
>
> It's a good article by a good source, but robably more than he wants to
> know, as it's not directly concerned with thermal production.
>
> The thermals we like so much use air heated primarily by conduction from
> the aforementioned hot objects, but I believe some "micro" (my term)
> convection near the ground is important for making the warm layer near
> the ground thicker than conduction alone would provide.
>
> --
> Eric Greenwell - Washington State, USA
> * Change "netto" to "net" to email me directly

Bill,

Back to the basics, heat is transfered in general by three methods
conduction, convection and radiation (http://www.mansfieldct.org/
schools/MMS/staff/hand/convcondrad.htm).

Radiation is not radioactive but transfer from a warm body (the sun in
our case) to a cooler body (the earth) by waves. As you stated the
air is mostly transparent to the waves so most of the energy passes
through and hits the surface below. As you stated some of the energy
is absorbed by the atmosphere (air, water vapor, dust, smog, etc),
some is scattered (bent so it goes off at an angle and and some is
reflected back to space.

The radiative energy that reaches the earth is transfered into heat or
water vapor generally. The warmed earth then transfers the heat to
the air above it by a combination of conduction (the act of
transferring energy from one molecule to the next by vibrational
energy and direct contact) or conduction (the transfer of energy from
the flow of molecules over a warm surface).

In general thermals are generated by a combination of conduction and
convection and you have probably noticed that the best soaring days
generally have at least a slight wind to help induce more heat
transfer by causing more convection rather than by just conduction
alone. The heat transfer from the earth to the air is driven by the
driving force of the difference in temperature between the air and the
ground. If there is not airflow the layer of air above the ground
quickly heats up and nearly matches the ground temperature so the heat
transfer slows down. Having a little convection as Eric said helps
mix the air up and keeps cooler air near the hotter ground to allow
greater amount of heat to be transfered to the air and therefore more
energy that can by turned into thermals.

[Tim Taylor]

On Oct 8, 8:52*pm, Eric Greenwell > wrote:
> Jim Logajan wrote:
> > " > wrote:
> >> The sun shines down through the atmosphere, hits things on the ground,
> >> the things on the ground get hot, and then the hot things on the
> >> ground heat the air?
>
> >> Sun light passing through the air does not heat the air at all? *Heats
> >> the air some but not much?
>
> >> If the air is transparent to solar energy, how is *the air able to
> >> pick up so much energy from hot objects on the ground?
>
> > Try reading the content of this web page for some basic answers to all your
> > questions:
>
> >http://www.ucar.edu/learn/1_1_1.htm
>
> It's a good article by a good source, but robably more than he wants to
> know, as it's not directly concerned with thermal production.
>
> The thermals we like so much use air heated primarily by conduction from
> the aforementioned hot objects, but I believe some "micro" (my term)
> convection near the ground is important for making the warm layer near
> the ground thicker than conduction alone would provide.
>
> --
> Eric Greenwell - Washington State, USA
> * Change "netto" to "net" to email me directly

Bill,

Back to the basics, heat is transfered in general by three methods
conduction, convection and radiation (http://www.mansfieldct.org/
schools/MMS/staff/hand/convcondrad.htm).

Radiation is not radioactive but transfer from a warm body (the sun
in
our case) to a cooler body (the earth) by waves. As you stated the
air is mostly transparent to the waves so most of the energy passes
through and hits the surface below. As you stated some of the energy
is absorbed by the atmosphere (air, water vapor, dust, smog, etc),
some is scattered (bent so it goes off at an angle and and some is
reflected back to space.

The radiative energy that reaches the earth is transfered into heat
or
water vapor generally. The warmed earth then transfers the heat to
the air above it by a combination of conduction (the act of
transferring energy from one molecule to the next by vibrational
energy and direct contact) or convection (the transfer of energy from
the flow of molecules over a warm surface).

In general thermals are generated by a combination of conduction and
convection and you have probably noticed that the best soaring days
generally have at least a slight wind to help induce more heat
transfer by causing more convection rather than by just conduction
alone. The heat transfer from the earth to the air is driven by the
driving force of the difference in temperature between the air and
the
ground. If there is not airflow the layer of air above the ground
quickly heats up and nearly matches the ground temperature so the
heat
transfer slows down. Having a little convection as Eric said helps
mix the air up and keeps cooler air near the hotter ground to allow
greater amount of heat to be transfered to the air and therefore more
energy that can by turned into thermals.

[Nine Bravo Ground]

On Oct 8, 9:55*pm, Tim Taylor > wrote:
> On Oct 8, 8:52*pm, Eric Greenwell > wrote:
>
>
>
>
>
> > Jim Logajan wrote:
> > > " > wrote:
> > >> The sun shines down through the atmosphere, hits things on the ground,
> > >> the things on the ground get hot, and then the hot things on the
> > >> ground heat the air?
>
> > >> Sun light passing through the air does not heat the air at all? *Heats
> > >> the air some but not much?
>
> > >> If the air is transparent to solar energy, how is *the air able to
> > >> pick up so much energy from hot objects on the ground?
>
> > > Try reading the content of this web page for some basic answers to all your
> > > questions:
>
> > >http://www.ucar.edu/learn/1_1_1.htm
>
> > It's a good article by a good source, but robably more than he wants to
> > know, as it's not directly concerned with thermal production.
>
> > The thermals we like so much use air heated primarily by conduction from
> > the aforementioned hot objects, but I believe some "micro" (my term)
> > convection near the ground is important for making the warm layer near
> > the ground thicker than conduction alone would provide.
>
> > --
> > Eric Greenwell - Washington State, USA
> > * Change "netto" to "net" to email me directly
>
> Bill,
>
> Back to the basics, heat is transfered in general by three methods
> conduction, convection and radiation (http://www.mansfieldct.org/
> schools/MMS/staff/hand/convcondrad.htm).
>
> Radiation is not radioactive but transfer from a warm body (the sun
> in
> our case) to a cooler body (the earth) by waves. *As you stated the
> air is mostly transparent to the waves so most of the energy passes
> through and hits the surface below. *As you stated some of the energy
> is absorbed by the atmosphere (air, water vapor, dust, smog, etc),
> some is scattered (bent so it goes off at an angle and and some is
> reflected back to space.
>
> The radiative energy that reaches the earth is transfered into heat
> or
> water vapor generally. *The warmed earth then transfers the heat to
> the air above it by a combination of conduction (the act of
> transferring energy from one molecule to the next by vibrational
> energy and direct contact) or convection (the transfer of energy from
> the flow of molecules over a warm surface).
>
> In general thermals are generated by a combination of conduction and
> convection and you have probably noticed that the best soaring days
> generally have at least a slight wind to help induce more heat
> transfer by causing more convection rather than by just conduction
> alone. *The heat transfer from the earth to the air is driven by the
> driving force of the difference in temperature between the air and
> the
> ground. *If there is not airflow the layer of air above the ground
> quickly heats up and nearly matches the ground temperature so the
> heat
> transfer slows down. *Having a little convection as Eric said helps
> mix the air up and keeps cooler air near the hotter ground to allow
> greater amount of heat to be transfered to the air and therefore more
> energy that can by turned into thermals.

The other kind of radiation can heat things up too.

9B

[T8]

On Oct 9, 12:55*am, Tim Taylor > wrote:
> On Oct 8, 8:52*pm, Eric Greenwell > wrote:
>
>
>
> > Jim Logajan wrote:
> > > " > wrote:
> > >> The sun shines down through the atmosphere, hits things on the ground,
> > >> the things on the ground get hot, and then the hot things on the
> > >> ground heat the air?
>
> > >> Sun light passing through the air does not heat the air at all? *Heats
> > >> the air some but not much?
>
> > >> If the air is transparent to solar energy, how is *the air able to
> > >> pick up so much energy from hot objects on the ground?
>
> > > Try reading the content of this web page for some basic answers to all your
> > > questions:
>
> > >http://www.ucar.edu/learn/1_1_1.htm
>
> > It's a good article by a good source, but robably more than he wants to
> > know, as it's not directly concerned with thermal production.
>
> > The thermals we like so much use air heated primarily by conduction from
> > the aforementioned hot objects, but I believe some "micro" (my term)
> > convection near the ground is important for making the warm layer near
> > the ground thicker than conduction alone would provide.
>
> > --
> > Eric Greenwell - Washington State, USA
> > * Change "netto" to "net" to email me directly
>
> Bill,
>
> Back to the basics, heat is transfered in general by three methods
> conduction, convection and radiation (http://www.mansfieldct.org/
> schools/MMS/staff/hand/convcondrad.htm).
>
> Radiation is not radioactive but transfer from a warm body (the sun
> in
> our case) to a cooler body (the earth) by waves. *As you stated the
> air is mostly transparent to the waves so most of the energy passes
> through and hits the surface below. *As you stated some of the energy
> is absorbed by the atmosphere (air, water vapor, dust, smog, etc),
> some is scattered (bent so it goes off at an angle and and some is
> reflected back to space.
>
> The radiative energy that reaches the earth is transfered into heat
> or
> water vapor generally. *The warmed earth then transfers the heat to
> the air above it by a combination of conduction (the act of
> transferring energy from one molecule to the next by vibrational
> energy and direct contact) or convection (the transfer of energy from
> the flow of molecules over a warm surface).
>
> In general thermals are generated by a combination of conduction and
> convection and you have probably noticed that the best soaring days
> generally have at least a slight wind to help induce more heat
> transfer by causing more convection rather than by just conduction
> alone. *The heat transfer from the earth to the air is driven by the
> driving force of the difference in temperature between the air and
> the
> ground. *If there is not airflow the layer of air above the ground
> quickly heats up and nearly matches the ground temperature so the
> heat
> transfer slows down. *Having a little convection as Eric said helps
> mix the air up and keeps cooler air near the hotter ground to allow
> greater amount of heat to be transfered to the air and therefore more
> energy that can by turned into thermals.

Tim, Eric... think you guys need to check your sources.

Principle thermal input to lower atmosphere is long wave infrared from
the earth. Over 50% iirc, but don't have an authoritative ref handy.

Conduction in air is notoriously poor....

regards,
Evan Ludeman / T8

[John Smith]

> Conduction in air is notoriously poor....

As shown by devices like pullovers etc.

[T8]

On Oct 9, 7:19*am, T8 > wrote:

> Principle

Argh. Principal.

-T8

[Tim Taylor]

On Oct 9, 5:19*am, T8 > wrote:
> On Oct 9, 12:55*am, Tim Taylor > wrote:
>
>
>
>
>
> > On Oct 8, 8:52*pm, Eric Greenwell > wrote:
>
> > > Jim Logajan wrote:
> > > > " > wrote:
> > > >> The sun shines down through the atmosphere, hits things on the ground,
> > > >> the things on the ground get hot, and then the hot things on the
> > > >> ground heat the air?
>
> > > >> Sun light passing through the air does not heat the air at all? *Heats
> > > >> the air some but not much?
>
> > > >> If the air is transparent to solar energy, how is *the air able to
> > > >> pick up so much energy from hot objects on the ground?
>
> > > > Try reading the content of this web page for some basic answers to all your
> > > > questions:
>
> > > >http://www.ucar.edu/learn/1_1_1.htm
>
> > > It's a good article by a good source, but robably more than he wants to
> > > know, as it's not directly concerned with thermal production.
>
> > > The thermals we like so much use air heated primarily by conduction from
> > > the aforementioned hot objects, but I believe some "micro" (my term)
> > > convection near the ground is important for making the warm layer near
> > > the ground thicker than conduction alone would provide.
>
> > > --
> > > Eric Greenwell - Washington State, USA
> > > * Change "netto" to "net" to email me directly
>
> > Bill,
>
> > Back to the basics, heat is transfered in general by three methods
> > conduction, convection and radiation (http://www.mansfieldct.org/
> > schools/MMS/staff/hand/convcondrad.htm).
>
> > Radiation is not radioactive but transfer from a warm body (the sun
> > in
> > our case) to a cooler body (the earth) by waves. *As you stated the
> > air is mostly transparent to the waves so most of the energy passes
> > through and hits the surface below. *As you stated some of the energy
> > is absorbed by the atmosphere (air, water vapor, dust, smog, etc),
> > some is scattered (bent so it goes off at an angle and and some is
> > reflected back to space.
>
> > The radiative energy that reaches the earth is transfered into heat
> > or
> > water vapor generally. *The warmed earth then transfers the heat to
> > the air above it by a combination of conduction (the act of
> > transferring energy from one molecule to the next by vibrational
> > energy and direct contact) or convection (the transfer of energy from
> > the flow of molecules over a warm surface).
>
> > In general thermals are generated by a combination of conduction and
> > convection and you have probably noticed that the best soaring days
> > generally have at least a slight wind to help induce more heat
> > transfer by causing more convection rather than by just conduction
> > alone. *The heat transfer from the earth to the air is driven by the
> > driving force of the difference in temperature between the air and
> > the
> > ground. *If there is not airflow the layer of air above the ground
> > quickly heats up and nearly matches the ground temperature so the
> > heat
> > transfer slows down. *Having a little convection as Eric said helps
> > mix the air up and keeps cooler air near the hotter ground to allow
> > greater amount of heat to be transfered to the air and therefore more
> > energy that can by turned into thermals.
>
> Tim, Eric... think you guys need to check your sources.
>
> Principle thermal input to lower atmosphere is long wave infrared from
> the earth. *Over 50% iirc, but don't have an authoritative ref handy.
>
> Conduction in air is notoriously poor....
>
> regards,
> Evan Ludeman / T8

Evan,

While the long wave does have a greater input back into the total
atmosphere and to radiation back into space I think in the boundary
layer conduction and convection are still the primary sources of heat
transfer. Since the air is primarily oxygen and nitrogen that are
both opaque to long waves as well it it mostly the other sources that
generate thermals.

From: http://www.auf.asn.au/meteorology/section1b.html#atmospheric_temperature

1.7.4 Tropospheric transport of surface heating and cooling

The means by which surface heating or cooling is transported to the
lower troposphere are:

by conduction — air molecules coming into contact with the heated (or
cooled) surface are themselves heated (or cooled) and have the same
effect on adjacent molecules; thus an air layer only a few centimetres
thick becomes less (or more) dense than the air above

by convective mixing — occurs when the heated air layer tries to rise
and the denser layer above tries to sink. Thus small turbulent eddies
build and the heated layer expands from a few centimetres to a layer
hundreds, or thousands, of feet deep depending on the intensity of
solar heating; refer to section 3.3.1. Convective mixing is more
important than mechanical mixing for heating air, and is usually
dominant during daylight hours. In hot, dry areas of Australia the
convective mixing layer can extend beyond 10 000 feet

by mechanical mixing — where wind flow creates frictional turbulence;
refer to section 3.3.2. Mechanical mixing dominates nocturnally when
surface cooling and conduction create a cooler, denser layer above the
surface — thus stopping convective mixing. If there is no wind
mechanical mixing cannot occur, refer to section 3.4.

The term (planetary) boundary layer is used to describe the lowest
layer of the atmosphere, roughly 1000 to 6000 feet thick, in which the
influence of surface friction on air motion is important. It is also
referred to as the friction layer or the mixed layer. The boundary
layer will equate with the mechanical mixing layer if the air is
stable and with the convective mixing layer if the air is unstable.
The term surface boundary layer or surface layer is applied to the
thin layer immediately adjacent to the surface, and part of the
planetary boundary layer. Within this layer the friction effects are
more or less constant throughout, rather than decreasing with height,
and the effects of daytime heating and night-time cooling are at a
maximum. The layer is roughly 50 feet deep, and varies with conditions.

[T8]

On Oct 9, 10:47*am, Tim Taylor > wrote:

>
> Evan,
>
> While the long wave does have a greater input back into the total
> atmosphere and to radiation back into space I think in the boundary
> layer conduction and convection are still the primary sources of heat
> transfer. * *Since the air is primarily oxygen and nitrogen that are
> both opaque to long waves as well it it mostly the other sources that
> generate thermals.

Hey Tim,

I think you'll find if you dig into this that it's long wave
radiation, plus convection (thermals + wind) and evaporation/
condensation. Conduction is a bit player.

See second two answers here, though I cannot vouch for numbers
http://www.newton.dep.anl.gov/askasci/wea00/wea00082.htm -- the first
response given is in error. There must be something better on the
web, but I can't find it quickly.

What's missing here is useful info on absorption coefficients and heat
flux vs wavelength and water vapor content. But what I am given to
understand here is that most of the heat energy that drives thermals
we can use comes from long wave infrared transmitted from the heated
surface and absorbed in the first few feet / tens of feet / hundreds
of feet. I cheerfully admit I don't have the time to go get the
details to back up my case

Best,
Evan Ludeman / T8

[Frank[_12_]]

On Oct 8, 9:59*pm, " > wrote:
> The sun shines down through the atmosphere, hits things on the ground,
> the things on the ground get hot, and then the hot things on the
> ground heat the air?
>
> Sun light passing through the air does not heat the air at all? *Heats
> the air some but not much?
>
> If the air is transparent to solar energy, how is *the air able to
> pick up so much energy from hot objects on the ground?
>
> Bill
> 6W

Bill,

Solar (electromagnetic) energy in the visible light spectrum doesn't
couple very well to dry air. However, energy in the visible light
spectrum *does* couple nicely to darker objects like a dark farm field
or a parking lot, etc. The visible light energy heats the ground,
thereby converting visible light energy to much lower frequency
(longer wavelength) IR energy, and energy in the IR band *does* couple
to dry air in close contact with the hot objects. However, dry air is
a great insulator, so only the air a few centimeters/meters above the
ground gets heated directly, forming a mat of heated air underneath
colder air above. This is an unstable configuration, and thermals are
nature's mechanism for re-establishing equilibrium. This mechanism is
closely analogous to heating a pot of water on the stove. The water
immediately adjacent to the bottom of the pot gets hot, and this sets
up circulation currents to re-establish equilibrium in the rest of the
pot. If the heating is fast enough, local vaporization takes place
causing bubbles to form (i.e. the pot boils).

Just as an evolutionary side note, eyes evolved to see in the visible
spectrum *because* the air is transparent (i.e. very low coupling
coefficient) to that band of energy. If our atmosphere happened to be
only transparent to what we call infrared, then we'd all see in the
infrared, not the visible range, and thermals would be much easier to
"see" ;-).

Regards,

TA

[[email protected][_2_]]

On Oct 9, 8:37*pm, Frank > wrote:
> On Oct 8, 9:59*pm, " > wrote:
>
> > The sun shines down through the atmosphere, hits things on the ground,
> > the things on the ground get hot, and then the hot things on the
> > ground heat the air?
>
> > Sun light passing through the air does not heat the air at all? *Heats
> > the air some but not much?
>
> > If the air is transparent to solar energy, how is *the air able to
> > pick up so much energy from hot objects on the ground?
>
> > Bill
> > 6W
>
> Bill,
>
> Solar (electromagnetic) energy in the visible light spectrum doesn't
> couple very well to dry air. *However, energy in the visible light
> spectrum *does* couple nicely to darker objects like a dark farm field
> or a parking lot, etc. *The visible light energy heats the ground,
> thereby converting visible light energy to much lower frequency
> (longer wavelength) IR energy, and energy in the IR band *does* couple
> to dry air in close contact with the hot objects. *However, dry air is
> a great insulator, so only the air a few centimeters/meters above the
> ground gets heated directly, forming a mat of heated air underneath
> colder air above. *This is an unstable configuration, and thermals are
> nature's mechanism for re-establishing equilibrium. *This mechanism is
> closely analogous to heating a pot of water on the stove. *The water
> immediately adjacent to the bottom of the pot gets hot, and this sets
> up circulation currents to re-establish equilibrium in the rest of the
> pot. *If the heating is fast enough, local vaporization takes place
> causing bubbles to form (i.e. the pot boils).
>
> Just as an evolutionary side note, eyes evolved to see in the visible
> spectrum *because* the air is transparent (i.e. very low coupling
> coefficient) to that band of energy. *If our atmosphere happened to be
> only transparent to what we call infrared, then we'd all see in the
> infrared, not the visible range, and thermals would be much easier to
> "see" ;-).
>
> Regards,
>
> TA

Still air, like in a double pane window or fiberglass insulation,
seems to block heat tranfer. Moving air, like a car radiator or a
breeze, seems to heat the air and carry away heat. Neither the long
wave radition or conduction seems to explain how air is heated. As
you appoach a hot object with your hand, you feel radiation from the
hot object, not hot air. It seems that air velocity and mixing is the
key to heating air ? Dry air seems to heat much faster than damp
air?

Bill Snead

[mattm[_2_]]

On Oct 12, 9:11*pm, wrote:
> On Oct 9, 8:37*pm, Frank > wrote:
>
>
>
> > On Oct 8, 9:59*pm, " > wrote:
>
> > > The sun shines down through the atmosphere, hits things on the ground,
> > > the things on the ground get hot, and then the hot things on the
> > > ground heat the air?
>
> > > Sun light passing through the air does not heat the air at all? *Heats
> > > the air some but not much?
>
> > > If the air is transparent to solar energy, how is *the air able to
> > > pick up so much energy from hot objects on the ground?
>
> > > Bill
> > > 6W
>
> > Bill,
>
> > Solar (electromagnetic) energy in the visible light spectrum doesn't
> > couple very well to dry air. *However, energy in the visible light
> > spectrum *does* couple nicely to darker objects like a dark farm field
> > or a parking lot, etc. *The visible light energy heats the ground,
> > thereby converting visible light energy to much lower frequency
> > (longer wavelength) IR energy, and energy in the IR band *does* couple
> > to dry air in close contact with the hot objects. *However, dry air is
> > a great insulator, so only the air a few centimeters/meters above the
> > ground gets heated directly, forming a mat of heated air underneath
> > colder air above. *This is an unstable configuration, and thermals are
> > nature's mechanism for re-establishing equilibrium. *This mechanism is
> > closely analogous to heating a pot of water on the stove. *The water
> > immediately adjacent to the bottom of the pot gets hot, and this sets
> > up circulation currents to re-establish equilibrium in the rest of the
> > pot. *If the heating is fast enough, local vaporization takes place
> > causing bubbles to form (i.e. the pot boils).
>
> > Just as an evolutionary side note, eyes evolved to see in the visible
> > spectrum *because* the air is transparent (i.e. very low coupling
> > coefficient) to that band of energy. *If our atmosphere happened to be
> > only transparent to what we call infrared, then we'd all see in the
> > infrared, not the visible range, and thermals would be much easier to
> > "see" ;-).
>
> > Regards,
>
> > TA
>
> Still air, like in a double pane window or fiberglass insulation,
> seems to block heat tranfer. *Moving air, like a car radiator or a
> breeze, *seems to heat the air and carry away heat. *Neither the long
> wave radition or conduction seems to explain how air is heated. *As
> you appoach a hot object with your hand, you feel radiation from the
> hot object, not hot air. *It seems that air velocity and mixing is the
> key to heating air ? * Dry air seems to heat much faster than damp
> air?
>
> Bill Snead

Think of the shimmer when looking over hot ground in the summer. This
is the heating process in action. The shimmer is caused because the
first foot or two of air adjacent to the ground is much warmer than
the air
above it, and because of the temperature difference it has a different
refractive index (just like the pencil sticking out of a glass of
water looks bent).

Some amount of wind is helpful because
it will push the warmer air up against a wick of some type, which will
break the surface tension and allow the heated air to travel upwards
(e.g. cell phone tower, ridge, line of trees, even a body of water).

I think the issue with damp air is really damp ground. Water has a
much
higher heat content factor, i.e. it takes more energy to raise the
temperature
of water a degree than it does dry ground. Moist air is actually more
buoyant
because H2O molecules are lighter than N2 or O2 molecules but still
take
up the same room. Normally this is only a factor when other lifting
mechanisms are at work (because of damp ground not heating as well)
but it has a huge effect in creating storms.

-- Matt

[[email protected][_2_]]

On Oct 13, 10:10*am, mattm > wrote:
> On Oct 12, 9:11*pm, wrote:
>
>
>
>
>
> > On Oct 9, 8:37*pm, Frank > wrote:
>
> > > On Oct 8, 9:59*pm, " > wrote:
>
> > > > The sun shines down through the atmosphere, hits things on the ground,
> > > > the things on the ground get hot, and then the hot things on the
> > > > ground heat the air?
>
> > > > Sun light passing through the air does not heat the air at all? *Heats
> > > > the air some but not much?
>
> > > > If the air is transparent to solar energy, how is *the air able to
> > > > pick up so much energy from hot objects on the ground?
>
> > > > Bill
> > > > 6W
>
> > > Bill,
>
> > > Solar (electromagnetic) energy in the visible light spectrum doesn't
> > > couple very well to dry air. *However, energy in the visible light
> > > spectrum *does* couple nicely to darker objects like a dark farm field
> > > or a parking lot, etc. *The visible light energy heats the ground,
> > > thereby converting visible light energy to much lower frequency
> > > (longer wavelength) IR energy, and energy in the IR band *does* couple
> > > to dry air in close contact with the hot objects. *However, dry air is
> > > a great insulator, so only the air a few centimeters/meters above the
> > > ground gets heated directly, forming a mat of heated air underneath
> > > colder air above. *This is an unstable configuration, and thermals are
> > > nature's mechanism for re-establishing equilibrium. *This mechanism is
> > > closely analogous to heating a pot of water on the stove. *The water
> > > immediately adjacent to the bottom of the pot gets hot, and this sets
> > > up circulation currents to re-establish equilibrium in the rest of the
> > > pot. *If the heating is fast enough, local vaporization takes place
> > > causing bubbles to form (i.e. the pot boils).
>
> > > Just as an evolutionary side note, eyes evolved to see in the visible
> > > spectrum *because* the air is transparent (i.e. very low coupling
> > > coefficient) to that band of energy. *If our atmosphere happened to be
> > > only transparent to what we call infrared, then we'd all see in the
> > > infrared, not the visible range, and thermals would be much easier to
> > > "see" ;-).
>
> > > Regards,
>
> > > TA
>
> > Still air, like in a double pane window or fiberglass insulation,
> > seems to block heat tranfer. *Moving air, like a car radiator or a
> > breeze, *seems to heat the air and carry away heat. *Neither the long
> > wave radition or conduction seems to explain how air is heated. *As
> > you appoach a hot object with your hand, you feel radiation from the
> > hot object, not hot air. *It seems that air velocity and mixing is the
> > key to heating air ? * Dry air seems to heat much faster than damp
> > air?
>
> > Bill Snead
>
> Think of the shimmer when looking over hot ground in the summer. *This
> is the heating process in action. *The shimmer is caused because the
> first foot or two of air adjacent to the ground is much warmer than
> the air
> above it, and because of the temperature difference it has a different
> refractive index (just like the pencil sticking out of a glass of
> water looks bent).
>
> Some amount of wind is helpful because
> it will push the warmer air up against a wick of some type, which will
> break the surface tension and allow the heated air to travel upwards
> (e.g. cell phone tower, ridge, line of trees, even a body of water).
>
> I think the issue with damp air is really damp ground. *Water has a
> much
> higher heat content factor, i.e. it takes more energy to raise the
> temperature
> of water a degree than it does dry ground. *Moist air is actually more
> buoyant
> because H2O molecules are lighter than N2 or O2 molecules but still
> take
> up the same room. *Normally this is only a factor when other lifting
> mechanisms are at work (because of damp ground not heating as well)
> but it has a huge effect in creating storms.
>
> -- Matt- Hide quoted text -
>
> - Show quoted text -

Maybe the solar energy primarly reacts with (is absorbed by ) liquid
water. If there is a lot of water (the ocean a big lake), the mass of
water takes the energy but does not heat the air. However, if the
ground is what we think of dry, maybe the limited water grabs the
solar energy in a way that causes the air to heat quickly. In central
Texas in August typically the earth gets dry enough to wilt the
plants. As the plants turn brown, the maximum temperature will jump
from about 95 to maybe 102 F. The thermals will increase in strength
from about 350 feet per minute to over 500 feet per minute. In our
quarry the average moisture content of the crushed rock is about 6
percent. In the dry spells the moisture content of the rock never
falls below about 3 percent. So there is still a lot of water around
even though the place looks dry.

Bill Snead

[[email protected]]

I wonder if the sun does do this. right guys? Am i wrong? well the sun brings light down and produces the heat we have now.

[2G]

On Thursday, October 8, 2009 at 6:59:55 PM UTC-7, wrote:
> The sun shines down through the atmosphere, hits things on the ground,
> the things on the ground get hot, and then the hot things on the
> ground heat the air?
>
> Sun light passing through the air does not heat the air at all? Heats
> the air some but not much?
>
> If the air is transparent to solar energy, how is the air able to
> pick up so much energy from hot objects on the ground?
>
> Bill
> 6W

The atmospheric isn't totally transparent to solar radiation, but absorbs a portion of it before it reaches Earth. Solar irradiance at the troposphere is 1366 W/m^2; by the time it reaches Earth it has decreased to about 1000 W/m^2. The difference of 366 W/m^2 goes into heating the atmosphere. Of course the ground reradiates infrared energy it absorbs back into the atmosphere.

Tom

[[email protected]]

On Thursday, October 8, 2009 at 7:59:55 PM UTC-6, wrote:
> The sun shines down through the atmosphere, hits things on the ground,
> the things on the ground get hot, and then the hot things on the
> ground heat the air?
>
> Sun light passing through the air does not heat the air at all? Heats
> the air some but not much?
>
> If the air is transparent to solar energy, how is the air able to
> pick up so much energy from hot objects on the ground?
>
> Bill
> 6W

[Duster]

Not exactly transparent. The sky appears blue because air molecules and suspended particles absorb and scatter certain wavelengths of light. This energy is transduced from photons into heat. However, the majority of advection is due to the previous explanation. Not a physicist, so someone else take a stab.

[Jim White[_3_]]

At 20:17 27 March 2017, Duster wrote:
>Not exactly transparent. The sky appears blue because air molecules and
>sus=
>pended particles absorb and scatter certain wavelengths of light. This
>ener=
>gy is transduced from photons into heat. However, the majority of
>advection=
> is due to the previous explanation. Not a physicist, so someone else
take
>=
>a stab.
>
The downward energy radiated by the sun is short wave and not absorbed by
the atmosphere. The upward energy radiated by the ground is long wave which
is.

[Tango Whisky]

Le mercredi 29 mars 2017 10:00:08 UTC+2, Jim White a écritÂ*:
> At 20:17 27 March 2017, Duster wrote:
> >Not exactly transparent. The sky appears blue because air molecules and
> >sus=
> >pended particles absorb and scatter certain wavelengths of light. This
> >ener=
> >gy is transduced from photons into heat. However, the majority of
> >advection=
> > is due to the previous explanation. Not a physicist, so someone else
> take
> >=
> >a stab.
> >
> The downward energy radiated by the sun is short wave and not absorbed by
> the atmosphere. The upward energy radiated by the ground is long wave which
> is.

That's not correct.
The energy radiated upward is in the 10 micron region, and the only constituet of the atmosphere which absorbs infrared is CO2. Which accounts to 400 ppm.

So, it's rather that the grounds heats the adjacent air by heat conduction, not by radiation.

[WaltWX[_2_]]

Sometimes a good meteorology text book that covers topics like atmospheric physics, radiation, optics and the boundary layer meteorology (thermal layer) would answer a lot of the r.a.s questions.

Here's a very complete, up to date and recently published one that you can read on-line or download the pdf for free!

If you are an engineer, you'll love this book because it explains meteorology with equations and examples... no derivations.

"Practical Meteorology - An Algebra-based Survey of Atmospheric Science" (www.eosas.ubc.ca/book/Practical_Meteorology). I haven't reviewed it, but it does have a very comprehensive 35 page chapter on Boundary Layer Meteorology written by someone who writes well and knows what he's talking about.

I met Dr Stull from the University of British Columbia Vancouver last January and he suggested his book. Dr Stull published in 1986 the classic book on Boundary Layer meteorology. He tried to publish this recent text book... but gave up and made it freely available.

Walt Rogers WX

[Paul B[_2_]]

Hi Walt

Sounds interesting, however the site cannot be reached. Could you please check the URL and repost?

Thanks

Paul

[danlj]

https://www.eoas.ubc.ca/books/Practical_Meteorology/

[Dan Marotta]

Thanks for that! Wish I'd had it in December, but I'll start chipping
away, nonetheless.

On 4/1/2017 11:58 PM, danlj wrote:
> https://www.eoas.ubc.ca/books/Practical_Meteorology/

--
Dan, 5J

[[email protected]]

On Sunday, April 2, 2017 at 11:31:39 AM UTC-5, Dan Marotta wrote:
> Thanks for that! Wish I'd had it in December, but I'll start chipping
> away, nonetheless.
>
> On 4/1/2017 11:58 PM, danlj wrote:
> > https://www.eoas.ubc.ca/books/Practical_Meteorology/
>
> --
> Dan, 5J

Good Book! Chapter 3, pg. 68:

"....At the surface this effective flux is entirely due
to molecular conduction, and above about 5 mm altitude
the effective flux is mostly due to turbulence."

[[email protected]]

Is is a great question, and one I am currently working with. Our understanding of the atmosphere, I think, is incomplete, and needs reviewed and updating. Doing so will easily explain such a problem. As it stands there are deep contradictions and paradoxes associated with radiation and the atmosphere.
Air is a near perfect insulator (it has a conduction value of near zero; 0.024 no units) so the thought heat energy is transferred this way cannot be so .
Add to that: air is assumed to (with the exception of about 1% greenhouse gases) not absorb or emit any IR radiation: this is a contradiction to Radiation theory, and quantum mechanics where all matter above absolute 0 Kelvin radiates IR.

So something is wrong, because the air does increase, and decrease in temperature, and does so quickly.
My hypothesis is O2 and N2 (99% of the dry atmosphere) do absorb and emit IR radiation: I have the quantum theory to show where they do, the experimental instrument to show it does, and the application proof to show it does.

I am currently writing up my work - it is a massive undertaking; I predict the biggest upset is science of our time: greenhouse theory will collapse. Special greenhouse atmosphere theory is pre quantum mechanics 19th Century science; it has not been updated with 20th Century knowledge - yet.

[Steve Koerner]

Don't forget to include water vapor in your hypothesising:

https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water



On Sunday, November 12, 2017 at 10:44:48 AM UTC-7, wrote:
> Is is a great question, and one I am currently working with. Our understanding of the atmosphere, I think, is incomplete, and needs reviewed and updating. Doing so will easily explain such a problem. As it stands there are deep contradictions and paradoxes associated with radiation and the atmosphere.
> Air is a near perfect insulator (it has a conduction value of near zero; 0.024 no units) so the thought heat energy is transferred this way cannot be so .
> Add to that: air is assumed to (with the exception of about 1% greenhouse gases) not absorb or emit any IR radiation: this is a contradiction to Radiation theory, and quantum mechanics where all matter above absolute 0 Kelvin radiates IR.
>
> So something is wrong, because the air does increase, and decrease in temperature, and does so quickly.
> My hypothesis is O2 and N2 (99% of the dry atmosphere) do absorb and emit IR radiation: I have the quantum theory to show where they do, the experimental instrument to show it does, and the application proof to show it does..
>
> I am currently writing up my work - it is a massive undertaking; I predict the biggest upset is science of our time: greenhouse theory will collapse.. Special greenhouse atmosphere theory is pre quantum mechanics 19th Century science; it has not been updated with 20th Century knowledge - yet.

[Dan Marotta]

I kinda lost faith in wikipedia after a former global warming evangelist
turned "climate change denier" found his wiki entries deleted almost as
quickly as he would post them.Â* Are they, too, bearers of the banner?

On 11/13/2017 9:07 PM, Steve Koerner wrote:
> Don't forget to include water vapor in your hypothesising:
>
> https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water
>
>
>
> On Sunday, November 12, 2017 at 10:44:48 AM UTC-7, wrote:
>> Is is a great question, and one I am currently working with. Our understanding of the atmosphere, I think, is incomplete, and needs reviewed and updating. Doing so will easily explain such a problem. As it stands there are deep contradictions and paradoxes associated with radiation and the atmosphere.
>> Air is a near perfect insulator (it has a conduction value of near zero; 0.024 no units) so the thought heat energy is transferred this way cannot be so .
>> Add to that: air is assumed to (with the exception of about 1% greenhouse gases) not absorb or emit any IR radiation: this is a contradiction to Radiation theory, and quantum mechanics where all matter above absolute 0 Kelvin radiates IR.
>>
>> So something is wrong, because the air does increase, and decrease in temperature, and does so quickly.
>> My hypothesis is O2 and N2 (99% of the dry atmosphere) do absorb and emit IR radiation: I have the quantum theory to show where they do, the experimental instrument to show it does, and the application proof to show it does.
>>
>> I am currently writing up my work - it is a massive undertaking; I predict the biggest upset is science of our time: greenhouse theory will collapse. Special greenhouse atmosphere theory is pre quantum mechanics 19th Century science; it has not been updated with 20th Century knowledge - yet.

--
Dan, 5J

[[email protected]]

Sigh ... there's a great deal of misinformation here. A correct answer is long and complicated, but the short of it is that there are numerous gas absorption bands in the "solar shortwave" -- these range from the Hartley-Huggins bands of Ozone in the UV (responsible for the stratosphere), the Chappuis band of O3 in the mid visible, a variety of weak absorption bands of Oxygen, and then a substantial H2O absorption band at 940 nm ... with increasing numbers of absorption bands in the near infrared due to a variety of trace gases starting with H2O and CO2.

So sunlight can and does heat the atmosphere through direct absorption; absorbing aerosols also play a role.

Nonetheless, as is everybody's direct experience -- a lot of light gets down to the ground on a cloud-free day.

[2G]

On Tuesday, November 14, 2017 at 9:01:17 AM UTC-8, Dan Marotta wrote:
> I kinda lost faith in wikipedia after a former global warming evangelist
> turned "climate change denier" found his wiki entries deleted almost as
> quickly as he would post them.Â* Are they, too, bearers of the banner?
>
> On 11/13/2017 9:07 PM, Steve Koerner wrote:
> > Don't forget to include water vapor in your hypothesising:
> >
> > https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water
> >
> >
> >
> > On Sunday, November 12, 2017 at 10:44:48 AM UTC-7, wrote:
> >> Is is a great question, and one I am currently working with. Our understanding of the atmosphere, I think, is incomplete, and needs reviewed and updating. Doing so will easily explain such a problem. As it stands there are deep contradictions and paradoxes associated with radiation and the atmosphere.
> >> Air is a near perfect insulator (it has a conduction value of near zero; 0.024 no units) so the thought heat energy is transferred this way cannot be so .
> >> Add to that: air is assumed to (with the exception of about 1% greenhouse gases) not absorb or emit any IR radiation: this is a contradiction to Radiation theory, and quantum mechanics where all matter above absolute 0 Kelvin radiates IR.
> >>
> >> So something is wrong, because the air does increase, and decrease in temperature, and does so quickly.
> >> My hypothesis is O2 and N2 (99% of the dry atmosphere) do absorb and emit IR radiation: I have the quantum theory to show where they do, the experimental instrument to show it does, and the application proof to show it does.
> >>
> >> I am currently writing up my work - it is a massive undertaking; I predict the biggest upset is science of our time: greenhouse theory will collapse. Special greenhouse atmosphere theory is pre quantum mechanics 19th Century science; it has not been updated with 20th Century knowledge - yet.
>
> --
> Dan, 5J

Right, a democratic organization isn't always democratic when zealots take it upon themselves to be societies censors because they know what truth is.

Tom

[Tango Whisky]

Le mardi 19 décembre 2017 05:20:26 UTC+1, a écritÂ*:
> Sigh ... there's a great deal of misinformation here. A correct answer is long and complicated, but the short of it is that there are numerous gas absorption bands in the "solar shortwave" -- these range from the Hartley-Huggins bands of Ozone in the UV (responsible for the stratosphere), the Chappuis band of O3 in the mid visible, a variety of weak absorption bands of Oxygen, and then a substantial H2O absorption band at 940 nm ... with increasing numbers of absorption bands in the near infrared due to a variety of trace gases starting with H2O and CO2.
>
> So sunlight can and does heat the atmosphere through direct absorption; absorbing aerosols also play a role.
>
> Nonetheless, as is everybody's direct experience -- a lot of light gets down to the ground on a cloud-free day.

Well of course you have a variety of absorption bands, but if you take absorption coefficients and spectral intensity into account, it all boils down to one thing: Albedo rules.

[Paul Ruskin[_2_]]

On Tuesday, December 19, 2017 at 4:20:26 AM UTC, wrote:
> Sigh ... there's a great deal of misinformation here. A correct answer is long and complicated, ...

Any chance of putting some numbers on it? At least approximately?

Where does the energy end up, and by which mechanism?

Paul

[[email protected]]

Agreed on the Albedo rules observation. I experienced low albedo recently but found that zinc, exercise, and weight loss brought it right back up. Changed my life.

[Dan Daly[_2_]]

On Tuesday, December 19, 2017 at 2:50:44 PM UTC-5, wrote:
> Agreed on the Albedo rules observation. I experienced low albedo recently but found that zinc, exercise, and weight loss brought it right back up. Changed my life.

I would have thought that Fettuccine Albedo would make you gain weight...

[Darryl Ramm]

I want to know if the sun can warm the latte in my cup holder. I'm also considering dual cup holders for redundancy.

[Eric Greenwell[_4_]]

Tango Whisky wrote on 12/19/2017 12:34 AM:
> Le mardi 19 décembre 2017 05:20:26 UTC+1, a écrit :
>> Sigh ... there's a great deal of misinformation here. A correct answer is long and complicated, but the short of it is that there are numerous gas absorption bands in the "solar shortwave" -- these range from the Hartley-Huggins bands of Ozone in the UV (responsible for the stratosphere), the Chappuis band of O3 in the mid visible, a variety of weak absorption bands of Oxygen, and then a substantial H2O absorption band at 940 nm ... with increasing numbers of absorption bands in the near infrared due to a variety of trace gases starting with H2O and CO2.
>>
>> So sunlight can and does heat the atmosphere through direct absorption; absorbing aerosols also play a role.
>>
>> Nonetheless, as is everybody's direct experience -- a lot of light gets down to the ground on a cloud-free day.
>
> Well of course you have a variety of absorption bands, but if you take absorption coefficients and spectral intensity into account, it all boils down to one thing: Albedo rules.

The air that makes our thermals is the air heated near the surface. Look at a RAOB
on a soaring day, and you can see the thin super-adiabatic layer near the surface,
then the much thicker adiabatic lay above to the inversion level. We all know some
surface areas get hotter than others and produce thermals, while any direct
heating of the atmosphere is uniform, and unlikely to produce thermals.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[[email protected]]

The people who really care about this stuff are climatologists (and climate modelers), and increasingly the solar power community. The issue as far as the soaring community is concerned is that most of the sunlight that is lost to absorption in the atmosphere is mostly-always lost

* UV is absorbed in the stratosphere; as far as total energy is concerned there is not much variability in what gets to the ground.

* Chappuis-band O3 absorption (in the visible red) can change the surface heat flux a few percent, no more

* the big H2O band at 940 nm is very important climatologically .. but is perhaps 5% of total energy flux and not as variable as people might think

* H2O and CO2 (and some others) at wavelengths > 1.4 microns lead to substantial extinctions in the 1.4 -> 3 micron wavelength domains -- but our human eyes don't see that, the sun's solar output is decreasing at longer wavelengths, nor do silicon solar cells get energy from these wavelengths.

When you look at energy balance commonly more than 20% of the sun's radiation is absorbed in the atmosphere, and this is very important to the thermal structure of the atmosphere, but it isn't highly variable (as a fraction of total energy) so people just don't pay too much attention to it, for purposes like soaring.

This energy ends up as heat, distributed non-uniformly through the atmospheric column. The most blatantly obvious effect is that we have a stratosphere; there are also climatically-important consequences to this in the troposphere. Most of this heat is deposited at altitudes where we don't fly.

The dominant issues that effect lower-boundary layer heating rates are pretty obvious: clouds! Yes, surface-albedo ... and then a very large factor not discussed here is what meteorologists call the "Bowen ratio:" the ratio of the latent-to-sensible heat flux from the surface ... how much of the heat is used to evaporate water.

Deserts are good for soaring because most of the captured radiation does go to sensible heat.

A "secret" most western pilots don't know -- the best soaring season in the northeast is spring, before the trees leaf out. It's our desert. After they leaf out ... then every damned tree is a water-sucking nuisance ... and a subtle point is that deciduous trees flux more water than conifers ... there are easily-observable differences in Bowen-ratio from deciduous vs conifer forests.

More subtly there is a second "good" period in the fall when the trees lose their leaves, although with the declining sunlight it's not really great. But since the time of Benjamin Franklin naturalists noted that stream flows in the northeast jump after the trees lose their leaves in the fall, and correctly attributed the reason for this.

One of several reasons "the high ground" is usually better soaring (everywhere) is that water runs off it; the trees are almost always water-stress limited and shifted to species (conifers) that do that better. A water-stressed tree keeps its stomata closed: doesn't flux water but also cannot photosynthesize.

Plants do change the surface albedo, usually lower it. Plants look green because they don't use green light, and they want to reflect it to avoid its heat. They also increase the albedo at longer wavelengths. But this effect on albedo is usually less important that their water flux ... if they aren't water stressed.

Soil moisture can be measured (sort-of) by remote sensing in the microwave, and there are very large variations in soil moisture temporally (ask any farmer), but also spatially across the terrain ... in places (not our western deserts) where there's enough water for plants to grow generously.

Hey Eric Greenwell? You still flying around Richland Washington? I flew with you, and towed you years ago when I worked at PNL. It's pretty arid out there ... but nobody finds good thermals coming up off the big irrigated crop circles. In desert terrains stay away from green like the plague.

In the northeast the hierarchy is plowed-fields better than conifers, conifers better than growing hay or corn UNLESS the farmers are complaining about a dry spell, say out of the river bottoms and anywhere with deciduous trees, worse yet willows.

[Eric Greenwell[_4_]]

wrote on 12/19/2017 6:28 PM:
> Hey Eric Greenwell? You still flying around Richland Washington? I flew with you, and towed you years ago when I worked at PNL. It's pretty arid out there ... but nobody finds good thermals coming up off the big irrigated crop circles. In desert terrains stay away from green like the plague.

Yes, I am! Retired for a long time now, but still flying, but with motorgliders.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[Michael Opitz]

At 02:28 20 December 2017, wrote:
>The people who really care about this stuff are climatologists (and
>climate=
> modelers), and increasingly the solar power community. The
issue as far
>a=
>s the soaring community is concerned is that most of the sunlight
that is
>l=
>ost to absorption in the atmosphere is mostly-always lost=20
>
>* UV is absorbed in the stratosphere; as far as total energy is
concerned
>=
>there is not much variability in what gets to the ground. =20
>
>* Chappuis-band O3 absorption (in the visible red) can change the
surface
>=
>heat flux a few percent, no more
>
>* the big H2O band at 940 nm is very important climatologically ..
but is
>p=
>erhaps 5% of total energy flux and not as variable as people might
think=20
>
>* H2O and CO2 (and some others) at wavelengths > 1.4 microns
lead to
>substa=
>ntial extinctions in the 1.4 -> 3 micron wavelength domains -- but
our
>huma=
>n eyes don't see that, the sun's solar output is decreasing at longer
>wavel=
>engths, nor do silicon solar cells get energy from these
wavelengths. =20
>
>When you look at energy balance commonly more than 20% of the
sun's
>radiati=
>on is absorbed in the atmosphere, and this is very important to the
>thermal=
> structure of the atmosphere, but it isn't highly variable (as a
fraction
>o=
>f total energy) so people just don't pay too much attention to it,
for
>purp=
>oses like soaring.
>
>This energy ends up as heat, distributed non-uniformly through the
>atmosphe=
>ric column. The most blatantly obvious effect is that we have a
>stratosphe=
>re; there are also climatically-important consequences to this in
the
>trop=
>osphere. Most of this heat is deposited at altitudes where we
don't fly.
>=
>=20
>
>The dominant issues that effect lower-boundary layer heating rates
are
>pret=
>ty obvious: clouds! Yes, surface-albedo ... and then a very large
factor
>n=
>ot discussed here is what meteorologists call the "Bowen ratio:"
the ratio
>=
>of the latent-to-sensible heat flux from the surface ... how much of
the
>he=
>at is used to evaporate water.
>
>Deserts are good for soaring because most of the captured
radiation does
>go=
> to sensible heat. =20
>
>A "secret" most western pilots don't know -- the best soaring
season in
>th=
>e northeast is spring, before the trees leaf out. It's our desert.
After
>=
>they leaf out ... then every damned tree is a water-sucking
nuisance ...
>an=
>d a subtle point is that deciduous trees flux more water than
conifers ...
>=
>there are easily-observable differences in Bowen-ratio from
deciduous vs
>co=
>nifer forests. =20
>
>More subtly there is a second "good" period in the fall when the
trees
>lose=
> their leaves, although with the declining sunlight it's not really
great.
>=
> But since the time of Benjamin Franklin naturalists noted that
stream
>flow=
>s in the northeast jump after the trees lose their leaves in the fall,
and
>=
>correctly attributed the reason for this.
>
>One of several reasons "the high ground" is usually better soaring
>(everywh=
>ere) is that water runs off it; the trees are almost always water-
stress
>li=
>mited and shifted to species (conifers) that do that better. A
>water-stres=
>sed tree keeps its stomata closed: doesn't flux water but also
cannot
>photo=
>synthesize.=20
>
>Plants do change the surface albedo, usually lower it. Plants look
green
>b=
>ecause they don't use green light, and they want to reflect it to
avoid
>its=
> heat. They also increase the albedo at longer wavelengths. But
this
>eff=
>ect on albedo is usually less important that their water flux ... if
they
>a=
>ren't water stressed.
>
>Soil moisture can be measured (sort-of) by remote sensing in the
>microwave,=
> and there are very large variations in soil moisture temporally
(ask any
>f=
>armer), but also spatially across the terrain ... in places (not our
>wester=
>n deserts) where there's enough water for plants to grow
generously. =20
>
>Hey Eric Greenwell? You still flying around Richland Washington? I
flew
>w=
>ith you, and towed you years ago when I worked at PNL. It's
pretty arid
>ou=
>t there ... but nobody finds good thermals coming up off the big
irrigated
>=
>crop circles. In desert terrains stay away from green like the
plague.
>
>In the northeast the hierarchy is plowed-fields better than conifers,
>conif=
>ers better than growing hay or corn UNLESS the farmers are
complaining
>abou=
>t a dry spell, say out of the river bottoms and anywhere with
deciduous
>tre=
>es, worse yet willows. =20
>

Thanks for a great post!

RO

[[email protected]]

Yes thanks for a great post! I find it interesting that the "dry" river beds, and the "wet" cattle tanks out west seem to produce great thermals. I have always attributed that to a "low" area allowing the heat bubble to pool to a larger size before being ripped off due to the wind. The late 1V, Carl Herold, always commented that you cant get good thermal days without a good 10-15 mph of wind to keep them releasing.

CH

[Dave Nadler]

On Tuesday, December 19, 2017 at 9:28:55 PM UTC-5, wrote:

Great, Thanks!
Now, about those beaver-pond thermals...

[[email protected]]

On Tuesday, December 19, 2017 at 9:39:31 PM UTC-5, Eric Greenwell wrote:
> wrote on 12/19/2017 6:28 PM:
> > Hey Eric Greenwell? You still flying around Richland Washington? I flew with you, and towed you years ago when I worked at PNL. It's pretty arid out there ... but nobody finds good thermals coming up off the big irrigated crop circles. In desert terrains stay away from green like the plague.
>
> Yes, I am! Retired for a long time now, but still flying, but with motorgliders.


I moved east to SUNY-Albany in '89 ... didn't fly for years. Got back into it about 4 years ago. I'm retiring gradually at the moment, have one more graduate student to push out the door. At the moment I have a Discus B and a Ka-6 that is in the process of a major rebuild.

My family is still in Seattle, I like flying out on the lee side of the Cascades ... if I can persuade Annie maybe we'll even move back ... but even if I don't do that I'll come out to Ephrata one of these days...

Cheers,

Lee

[[email protected]]

On Wednesday, December 20, 2017 at 9:42:19 AM UTC-5, wrote:
> Yes thanks for a great post! I find it interesting that the "dry" river beds, and the "wet" cattle tanks out west seem to produce great thermals. I have always attributed that to a "low" area allowing the heat bubble to pool to a larger size before being ripped off due to the wind. The late 1V, Carl Herold, always commented that you cant get good thermal days without a good 10-15 mph of wind to keep them releasing.
>
> CH

Wet places that produce thermals are the bane of meteorologist/sailplane pilots. They can drive you nuts. When I flew out west I felt I really understood the soaring boundary layer ... there was rarely anything going on that I couldn't confidently explain.

Starting to fly in the Northeast, flying from Saratoga (5B2) there's all kinds of WTF! stuff. We have some "persistent mysteries" about house thermals within 2 miles of the field.

One REALLY important thing to remember though is that all the really good soaring days happen after a cold front booms through. This is particularly true in the non-desert parts of the country -- basically the only time you can get even "decent" conditions for long flights.

After a cold front a lot of the heat isn't solar (particularly around us) .... it's stored heat in the surface. A good cold front (at jet-stream latitudes) can easily give you -30 °F drop in surface air temperatures (and a nicely near-adiabatic lapse rate) ... and the stored heat available from that can give you a lot of lift.

We have uncommon fall days in the NE that no western pilot "gets" -- days when the skies are gelid overcast at 10,000 ft, a bitter cold wind at the surface, and shockingly good lift ... 8 - 10 kts (that's really good lift out here). All of that is being driven by the extracted surface heat stored up through the previous warm-sector passage.

And in those conditions ... shallow water bodies are often great. Water has high heat capacity AND a little wind-stress can stir it, so the heat can be "mined" out of the top meter or so much more quickly than this heat could conduct up (soil has poor thermal conductivity).

What may be counterintuitive until you think about it is that this works best when the temperature is cold, near freezing. Under those conditions the Bowen ratio will be favorable -- little water can evaporate -- sensible heat flux is maximized.

Flying downwind of the Adirondacks also produces bafflingly complex "wave" phenomena and a great many cases where thermal & wave systems coexist, and also conditions where one can climb in clear air up alongside convective clouds. A lot of this is very hard to explain classically.

My take on some of this is that it is not wave really, instead it is convergence due to the Mohawk/Hudson drainage convergence ... but without a lot of data I can't get, hard to know.

But as Dr. Suess said: “From there to here, from here to there, funny things are everywhere!�

[Bruce Hoult]

On Wednesday, December 20, 2017 at 8:42:22 PM UTC+3, wrote:
> One REALLY important thing to remember though is that all the really good soaring days happen after a cold front booms through. This is particularly true in the non-desert parts of the country -- basically the only time you can get even "decent" conditions for long flights.

Yes. Or soaring the front of the front as it arrives! There is awesome lift in front of that wall of cloud. Sometimes I've done that for a couple of hours with a front that is moving at only 5 or 10 km/h. When it gets within 5 km or so of the airfield all the gliders dash back, hangar land, get everything quickly inside and close the doors. There's nothing like just getting a cup of coffee made in the clubhouse as it starts getting pounded with wind and rain five minutes after you locked up the hangar.

[Michael Opitz]

At 17:42 20 December 2017, wrote:

>Flying downwind of the Adirondacks also produces bafflingly
complex "wave" phenomena and a great many cases where thermal
& wave systems coexist, and also conditions where one can climb in
clear air up alongside convective clouds. A lot of this is very hard
to explain classically. =20

>My take on some of this is that it is not wave really, instead it is
convergence due to the Mohawk/Hudson drainage convergence ...
but without a lot of data I can't get, hard to know.
>

You should come down and visit us in Freehold, NY to experience
the Hudson/Catskill convergence, plus flying in the nothern
Catskills. I find it interesting and challenging, so that I'm not
often bored with the same old stuff....... Others who don't
understand the mechanisms just get frustrated a lot....

RO

[Michael Opitz]

At 17:42 20 December 2017, wrote:

>Flying downwind of the Adirondacks also produces bafflingly
complex "wave" phenomena and a great many cases where thermal
& wave systems coexist, and also conditions where one can climb in
clear air up alongside convective clouds. A lot of this is very hard
to explain classically. =20

>My take on some of this is that it is not wave really, instead it is
convergence due to the Mohawk/Hudson drainage convergence ...
but without a lot of data I can't get, hard to know.
>

You should come down and visit us in Freehold, NY to experience
the Hudson/Catskill convergence, plus flying in the nothern
Catskills. I find it interesting and challenging, so that I'm not
often bored with the same old stuff....... Others who don't
understand the mechanisms just get frustrated a lot....

RO

[BobW]

On 12/20/2017 6:24 PM, Michael Opitz wrote:
> At 17:42 20 December 2017, wrote:
>
>> Flying downwind of the Adirondacks also produces bafflingly
> complex "wave" phenomena and a great many cases where thermal & wave
> systems coexist, and also conditions where one can climb in clear air up
> alongside convective clouds. A lot of this is very hard to explain
> classically.
>
>> My take on some of this is that it is not wave really, instead it is
> convergence due to the Mohawk/Hudson drainage convergence ... but without
> a lot of data I can't get, hard to know.
>>
>
> You should come down and visit us in Freehold, NY to experience the
> Hudson/Catskill convergence, plus flying in the northern Catskills. I
> find it interesting and challenging, so that I'm not often bored with the
> same old stuff....... Others who don't understand the mechanisms just get
> frustrated a lot....
>
> RO

To your point of local geography creating "interesting and challenging"
conditions tending toward creation of continuing mental interest/engagement
for someone sufficiently savvy to've begun the process of "sussing conditions
out," and "a lot of frustration" for those "not yet there," a coupla thoughts...

1) I suspect "interesting and challenging" is true (in U.S. latitudes, anyway)
wherever mountains poke up into moving airmasses. It's sure true along
Colorado's Front Range in any event! (Really motivated readers/SSA members can
find in "Soaring" mag's archives an article elaborating on one person's [my]
Front Range soaring knowledge "awakening" centered on this very point.)

2) Mental airmass models matter - a lot!!!

Bob W.

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