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From: Don Klipstein on 22 Dec 2008 09:53
In article <8arok4d5gteparmsehc91aqmkl75prve8o(a)4ax.com>, Whata Fool wrote:
>don(a)manx.misty.com (Don Klipstein) wrote:
>
>>In article <0ikpj41k4v8j7oikln12bjsk3dg44hrc0g(a)4ax.com>, Whata Fool wrote:
>>>don(a)manx.misty.com (Don Klipstein) wrote:
>>>
>>>>In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, Bill
>>>>Ward wrote in part:
>>>[snip]
>>>>>Just keep in mind you can't actually heat a hot source from a cold
>>>>>target. All you can do is slow the rate of cooling of the hot source. The
>>>>>sky is cold, the surface is hot.
>>>>
>>>> GHGs will slow the cooling by making outgoing radiation from the surface
>>>>absorbed at a lower, warmer level, which radiates half its radiation
>>>>downward.
>>>[snip]
>>>> - Don Klipstein (don(a)misty.com)
>>>
>>>
>>> Do you mean "cooling of the surface", meaning the solid or
>>>liquid surface rather than the lower atmosphere?
>>>
>>>
>>> If N2 doesn't radiate much in longwave, then any cooling is
>>>faster than almost no cooling at all.
>>>
>>> All the atmospheric radiation physics is interesting, but we
>>>have a few men claiming life on Earth could suffer displacement or
>>>death if the increased CO2 causes a slower cooling of the lower
>>>atmosphere.
>>>
>>> If there was no radiation cooling of the lower atmosphere
>>>without any GHGs at all, is there some mystical way that more GHGs
>>>can cause slower cooling than 100 years ago.
>>
>> The lowest part of the atmosphere does get cooled by the surface.
>>And GHGs in the lower atmosphere have their radiation going towards the
>>surface, in addition to all of the radiation that the surface would have
>>received without them.
>>
>> And GHGs in the lower atmosphere don't merely cool - they receive
>>radiation from the surface and can be warmed.
>
> There is the normal warming in daytime even from IR through clouds,
>but any major warming always comes with wind shift.
>
> There is a constant loss of energy to space from the atmosphere,
>the atmosphere is never a source of energy as some writings seem to
>suggest.
>
>>> I am well aware of the temperature records and averaging,
>>>but physics works the same way all the time, and with zero GHGs
>>>equaling zero cooling, doesn't GHGs mean cooling, and more GHGs
>>>mean more cooling, and less GHGs mean less cooling.
>>
>> Except for GHGs making the surface warmer than otherwise by adding
>>radiation to that already heading to the surface, and GHGs in the lower
>>atmosphere can experience radiational warming from the surface.
>>
>>> Statements that are not consistent are confusing.
>>
>> - Don Klipstein (don(a)misty.com)
>
> I don't think you are really making the comparison of the present
>Earth and an Earth with an N2 and O2 atmosphere no GHGs or water.
>
> It is even bizarre that anyone would claim the atmosphere could be
>cooled more than at present by interaction with the surface, and that is
>what you seem to be claiming.
>
> I agree that GHGs in the lower atmosphere can and do return part
>of the surface radiation back to the surface, but even with clouds,
>there is cooling at night if the wind is not bringing warmer air.
>
> I don't understand the obsession with GHG theory, it is partially
>right but saying that the Earth would be 33 degrees colder without GHGs
>is a fallacy that might lead to the spectre of additional CO2 cooling
>the Earth instead of warming it.
>
> The big fallacy is in the big change in the station locations
>used in the averaging, there should be no confidence at all in the
>results of the change of dozens or hundreds of locations used, even
>if anomalies are used because some locations have different ranges
>of diurnal temperatures, and that can have an effect on the minimum
>temperature anomaly.

We do have lower troposphere temperature interpretations from satellite
data since 1979. Check out the "temperature lower troposphere" data from
RSS and the similar product from UAH.

> I suggest that a study of only maximum daily temperatures of
>only the same locations might show something entirely different.

Worldwide, I expect increase of GHGs to cause that to increase less.
Meanwhile, nighttime temperatures as well as daytime temperatures affect
snow and ice cover, and change of that affects how much sunlight Earth
absorbs.

- Don Klipstein (don(a)misty.com)
From: Bill Ward on 22 Dec 2008 11:51
On Mon, 22 Dec 2008 02:11:15 +0000, Don Klipstein wrote:

> In article <pan.2008.12.15.07.25.04.110636(a)REMOVETHISix.netcom.com>, Bill
> Ward wrote in part:
>
>>On Mon, 15 Dec 2008 03:49:54 +0000, Don Klipstein wrote:
>>
>>> In article <pan.2008.12.02.09.04.49.526817(a)REMOVETHISix.netcom.com>,
>>> Bill Ward wrote:
>>>>On Tue, 02 Dec 2008 05:55:11 +0000, Don Klipstein wrote:
>>>>
>>>>> In <pan.2008.11.26.21.17.23.310423(a)REMOVETHISix.netcom.com>, Bill
>>>>> Ward wrote:
>>>>
>>>>Do you think that the "wet adiabatic" environmental lapse rate is
>>>>related to latent heat, or is it simply less than the dry adiabatic
>>>>lapse rate because it's not at equilibrium?
>>>
>>> It is less due to latent heat.
>>>
>>> The "1 size fits all figures" that I have heard are 3.5 degrees F per
>>> 1,000 feet for the wet one and 5.4 degrees F per 1,000 feet for the dry
>>> one.
>>>
>>>>>> Is it primarily by radiative transfer, or convection? It seems to
>>>>>> me
>>>>>>it must be convective, simply because warm, wet air is less dense
>>>>>>than cold, dry air, and quickly rises to maintain the lapse rate.
>>>>>
>>>>> Much of the time the answer is a significant factor other than
>>>>> radiation and vertical convection. Much of the "global convection"
>>>>> involves air movement within a degree of horizontal, and often
>>>>> forming clouds when moving upwards. Sometimes the lapse rate there
>>>>> is between the "dry adiabatic" and the "wet adiabatic" rates and the
>>>>> clouds have billowy cumuliform tops or are cumuliform throughout.
>>>>> Sometimes "warm advection" occurs more at cloud-top level than at
>>>>> cloud-base level (from the windspeed being greater higher up in the
>>>>> troposphere), causing the clouds to be stratiform.
>>>>
>>>>OK, that all sounds plausible, but I'm not sure how much effect the
>>>>horizontal component would have, other than the obvious mixing.
>>>
>>> The horizontal component involves atmospheric heat transfer from the
>>> tropics to the poles. It is very significant. It leads to frontal
>>> inversions, which cover significant area ahead of warm fronts
>>> (including areas where the warm fronts fail to reach at the surface).
>>> It leads to existence of stratosphere at middle and upper latitudes at
>>> pressure levels below that of the tropical tropopause.
>>>
>>>>>>IR radiated from the surface would be quickly absorbed by WV, clouds,
>>>>>>CO2, and other GHGs, and at 500W/m^2 would be overwhelmed by the 10's
>>>>>>of kW/m^2 available from convection of latent heat.
>>>>>
>>>>> Half the Earth's surface has no clouds overhead at any altitude.
>>>>
>>>>Surely you mean "at any given time". Or are there really regions
>>>>comprising half the Earth's surface that have never had a cloud in the
>>>>sky?
>>>
>>> I did mean "at any given time", and "those given times" in "those
>>> given locations" account for half the world lacking clouds at any
>>> altitude.
>>
>>OK, I'll buy that as an average. But I'll bet the tropics are far more
>>likely to be cloudy than the polar regions, and that's where most of the
>>cooling occurs.
>>
>>>>> The surface manages to radiate *somewhat* to outer space at night
>>>>> when the air overhead is clear - otherwise there would be no such
>>>>> thing as nighttime frost when air 2 meters above the surface is at +2
>>>>> degrees C (a fairly common situation). Some of the outgoing
>>>>> radiation can easily be absorbed and reradiated a couple or a few
>>>>> times by GHGs, but net of that is upward (and upward net is reduced
>>>>> by increase of GHGs).
>>>>
>>>>OK, no argument with that. I look at it as the surface radiating to a
>>>>target warmer than 3K space, but it's the same math.
>>>>>
>>>>>>At night, convection stops, but cooling is not required at night.
>>>>>>Convection kicks in during the day, when cooling is needed.
>>>>>
>>>>> Cooling still occurs at night by radiation. 5 AM temperature has a
>>>>> great rate of being less than 10 PM temperature. Upper level of
>>>>> radiation by atmosphere at night has half of its radiation to outer
>>>>> space. That heat comes from radiation from surface - even if
>>>>> absorbed and reradiated a couple times along the way.
>>>>
>>>>Agreed. At night the flux is always outward.
>>>>
>>>>> The "upper radiation level" also varies greatly with wavelength.
>>>>
>>>>Do you mean the "effective radiating altitude", which is calculated, or
>>>>some sort of integrated spectrum involving all the photons reaching a
>>>>surface outside the atmosphere, like a satellite imager? Neither I,
>>>>nor apparently Google, is familiar withe the term "upper radiation
>>>>level".
>>>
>>> Looks like I did not choose wrds well - it should have been
>>> "effective
>>> radiating altitude".
>>>
>>> Keep in mind that the "effective radiating altitude" is very fuzzy,
>>> since some wavelengths radiated by the surface have good atmospheric
>>> transparency (and a fairly clear shot to space) as long as there are no
>>> clouds, others have low chance of reaching the 500 mb level without
>>> being absorbed, and some are in-between - with absorption and
>>> reradiation varying directly with concentration of GHGs.
>>
>>That's my point. It's not well enough known to claim 1.5W/m^2 is going
>>to make any difference at all. All it takes is a minor negative feedback
>>loop to correct for that small an effect.
>
> The Ice Ages having temperature swinging 10-plus K from slight periodic
> changes in insolation show that we have a lot of positive feedback.

Has that actually been shown, or just inferred? If there were
significant positive feedback, it would have shown up in the ice core
signal as an exponential runaway to the rail. For long term stability,
you need negative feedback.

>>>>>>I don't see how radiative cooling is even necessary below the cloud
>>>>>>tops, since there's plenty of cooling capacity from convection.
>>>>>
>>>>> When frost or dew forms on the ground and on cars and trucks, the
>>>>> heat
>>>>> loss has a very impressive rate of by being by radiation.
>>>>
>>>>True, but radiation is peanuts compared to the available cooling
>>>>capacity of latent heat during the day. If the surface radiation were
>>>>blocked, convection could easily make it up.
>>>
>>> What about on days when there is no convection past the 750 mb or so
>>> level for even a minute? (I see plenty of those even with sky
>>> half-clear and cumulus clouds present.) What about in Arctic and
>>> upper-midlatitude areas where change in radiation balance during the
>>> 18 or whatever hours per day with little convection has a
>>> significicant effect on snow/ice cover, and that affects how much
>>> solar radiation the surface absorbs?
>>
>>It's the total transferred power that counts. It doesn't take much
>>latent heat convection to make up for a lot of radiation. The place to
>>look for changes is where the cooling is greatest, not places which are
>>already being warmed by the tropics.
>
> Cooling is significant in the polar areas. The global insolation map
> in
> the Wiki article on insolation shows the polar areas getting about 1/3
> as much insolation as the tropics do. Cooling is even more than 1/3
> that of the tropics, since global circulation transfers heat from the
> tropics to the polar regions.

Doesn't that mean the tropics still provide the majority of the cooling?

> Where the surface can warm significantly before convection occurs is
> probably where the world can warm more if GHGs increase. I would also
> expect more warming in areas where warming reduces surface albedo.

Aren't those areas already colder than average?

>>>>>>Once the energy reaches the tropopause, as you imply, it's a pretty
>>>>>>straight shot to 3K deep space, since there's not much atmosphere
>>>>>>left to absorb IR.
>>>>>>
>>>>>>Perhaps it's easier to see if you look at the lapse rate as bounded
>>>>>>at the top by the effective radiating temperature, and consider the
>>>>>>surface temperatures as derived from that and the adiabatic lapse
>>>>>>rate.
>>>>>
>>>>> That gets complicated by half the troposphere having lack of
>>>>> clouds at
>>>>> any altitude, and there are separate adiabatic lapse rates for clear
>>>>> air and clouded air. The global atmospheric average is close to the
>>>>> "wet" one, leaving upward mobility of lapse rate in the clear half
>>>>> of the world and in clear layers of the atmosphere in the clouded
>>>>> half of the world.
>>>>
>>>>At any given point, the applicable lapse rate should be obvious,
>>>>depending on whether cloud is present. I'm not convinced the lower
>>>>"average" environmental lapse rate has much to do with latent heat. It
>>>>might just be off-equilibrium due to transport lags or the like.
>>>
>>> It just happens to be that the "average lapse rate below the
>>> tropopause" is close to the wet adiabatic one. Close to the equator,
>>> it is more than coincidental - global circulation (from atmosphere
>>> below_tropical_tropopause_pressure_level as-a-whole) being warmer
>>> towards the equator and cooler towards the poles has air in the
>>> intertropical convergence zone rising. That largely establishes the
>>> lapse rate in the ITCZ as being close to the wet adiabatic one from
>>> the levels of the bases of the deep tall tropical convective clouds
>>> to the tropical tropopauuse. Below that cloud base level where
>>> those clouds form, the lapse rate is close to the dry adiabatic one
>>> at hot times of the day, and less at other times.
>>>
>>> Although it sounds like global circulation merely forces upward air
>>> movement in the ITCZ and that should cause clouds other than the
>>> billowy cumulus of natural convection, those show up anyway (along
>>> with a lot of clear air). Surface temperature in the ITCZ is not
>>> uniform. For one thing, some parts of the ITCZ have daylight and
>>> others have night. Also, ocean currents cool the ITCZ unevenly. So,
>>> upward air movement in the ITCZ occurs in hotspots where natural
>>> convection is sufficient to account for the upward global atmospheric
>>> circulation in the ITCZ - and the clouds there are billowy
>>> thunderheads, with many having anvil tops.
>>
>>I've often seen precipitation falling out of the anvil, many times never
>>reaching the ground. The energy in a thunderstorm is staggering, and
>>seems far more than IR could ever provide. Most of that energy had to
>>have come from the surface, and there's really no way back down. It
>>seems to me it has to radiate to space.
>
> Little of the surface is covered by thunderheads.
>
> And the atmosphere at the level of tropical anviltops is so cold, that
> it actually experiences slight warming from radiation. The air
> eventually does cool by radiation where it descends.
>
>>Thermals are what got me started on this issue. I asked myself just how
>>much IR it would take to lift a sailplane at a thousand feet/minute. I
>>immediately had doubts that IR is significant. The energy is clearly
>>mechanical energy of convection, and the cloud (if any)sitting on top of
>>the thermal has to represent an order of magnitude more energy from
>>latent heat.
>>
>>Thermals may not be all that common on the average, but when they do
>>occur, they must carry orders of magnitude more energy than IR.
>>
>>When I look (longingly) at pictures of tropical islands, I see very
>>familiar looking clouds. I have to assume the dynamics are similar, and
>>that they are common in the tropics. So I need a lot of convincing
>>evidence before I'll believe their heat transfer ability is somehow
>>comparable to an already cold polar surface or similar situation. All
>>it would take is a slight modulation of humidity or lapse rate to have
>>large effects on the power transmitted, far greater than the 1.5W/m^2
>>CO2 forcing assumed in the climate models.
>
> I agree that tropical thunderstorms lift warm air accounting for
> thermal power densities many times the solar constant. However, that
> heat is mostly not radiated at the tropical tropopause - the anviltops
> are at about the same temperature as the surrounding clear air at the
> same altitude, and it is actually colder at that altitude in the tropics
> than in the middle latitudes.

I don't see why the actual region where it's radiated to space matters.
Once the heat is lifted, there's no way it can be pumped back down to the
warmer surface without radiating more energy to an even colder heat sink.

Cooling is cooling, no matter where it happens.

> Cooling of the tropics is ultimately mostly from radiation from
> altitudes lower than the tropical tropopause and from global
> circulation.

That seems plausible.

>>> Do keep in mind that there is global atmospheric circulation at
>>> altitudes and pressure levels that are troposphere in the tropics and
>>> stratosphere elsewhere. Air rising through the ITCZ to close to the
>>> 100 mb level does not all go down there but some descends elsewhere
>>> poleward. And a lot of that moves poleward at altitudes where the is
>>> little hope of convection to such level from the surface, due to
>>> surface being cooler than in the ITCZ. At some of these
>>> extratropical-stratospheric altitudes and pressure levels, atmosphere
>>> is even usually warmer than it is over the ITCZ because over the ITCZ
>>> it is so cold (from cooling by uplifting) that local radiation balance
>>> warms the air moving largely horizontally at/near the tropical
>>> tropopause level. It cools by radiation in order to descend
>>> elsewhere, with much of that done during the descent - especially in
>>> the polar regions.
>>
>>That seems reasonable, but I don't see how it really affects the
>>tropical convection cells. That's how the energy got up there in the
>>first place.
>
> I don't think radiation does much to tropical convection cells.
>
> But if the polar regions warm with increase in reception of solar
> radiation, then horizontal temperature gradient will decrease. That
> will slow global circulation, which means slightly less cooling of the
> tropics.

Why? It seems to me it might provide even more effective global cooling
by restricting the radiation to warmer areas, rather than letting the warm
air escape to the cooler poles. Remember the 4th power term.

> The tropics will warm slightly as a result, and the thunderstorms
> would have to become a little more intense.

Which would increase the latent heat component.

From: Bill Ward on 22 Dec 2008 12:42
On Mon, 22 Dec 2008 12:39:09 +0000, Don Klipstein wrote:

> In article <pan.2008.12.09.17.36.37.607052(a)REMOVETHISix.netcom.com>, Bill
> Ward wrote: (With snip of at least stuff already quoted more than 3 times)
>>On Tue, 09 Dec 2008 07:09:08 +0000, Don Klipstein wrote:
>>
>>> In <pan.2008.12.04.08.02.57.92862(a)REMOVETHISix.netcom.com>, B. Ward
>>> wrote:
>>>>On Thu, 04 Dec 2008 03:45:45 +0000, Don Klipstein wrote:
>
>>>>> But CO2 is close to blackbody within some range of wavelengths
>>>>> where
>>>>> emission is close to peak of a 218 K blackbody. And the range does
>>>>> widen somewhat when there is more CO2 in the atmosphere.
>>>>
>>>>Look at this graph:
>>>>
>>>>http://upload.wikimedia.org/wikipedia/commons/7/7c/Atmospheric_Transmission.png
>>>>
>>>>Now please tell me if you think the CO2 absorption spectrum (3rd graph)
>>>>is similar to the 210K blackbody emission spectrum line in the top
>>>>graph.
>>>
>>> I did not claim that - I merely claimed (using maybe better words now
>>> than before) that CO2 in the atmosphere radiates close as well as a
>>> blackbody does within the 15um-peaking band.
>>>
>>> The 210K spectrum does indeed have its peak close to CO2's 15 um
>>> band,
>>> so CO2's 15 um band will absorb and radiate some very significant
>>> amount at 210K.
>>
>>My guess from looking at the spectra would be less than half as much,
>>assuming the area under the spectrum is proportional to power.
>
> Yes, that band looks to me eyeball-estimate worth 20-25% of blackbody
> radiation at 210 K and less at higher temperatures.

That looks about right to me also. How can we carry on a decent argument
if you keep agreeing with me? ;-)

>> And water shares the band.
>
> The atmosphere according to the above link has around 50% transparency
> of water vapor in that band, though I'm sure that varies widely since
> concentration of water vapor in the atmosphere is far from constant.

So shouldn't any effect of changes in CO2 be reduced by roughly another
50% to account for the water vapor?

> In polar areas where surface temperature has more upward mobility,
> there is less water vapor and CO2 accounts for a higher percentage of
> GHG effect.
>
> Worldwide, CO2 accounts for 9-26% of GHG effect.

Have you seen any derivation of that figure other than the RealClimate
blog?

> I suspect the wide
> range is in large part due to water vapor concentration being very far
> from constant. Another factor is probably diversity of temperature
> shifting relative radiation abilities of different wavelength bands of
> different GHGs.

Those seem like important factors that should be measured, not estimated.

>>>>Assuming you agree they are different, please explain how CO2 bonds
>>>>could emit in wavelengths they can't absorb.
>
> <SNIP>
>
>>>>> CO2 acts fairly like a blackbody at wavelengths within the 15 um
>>>>> band.
>>>>> 15 um is a wavelength where a blackbody has spectral power
>>>>> distribution about 96% of peak.
>>>>
>>>>It appears to me both tails of a 210K blackbody spectrum are missing
>>>>(looks like about half the total area). Cold CO2 is not a black body -
>>>>it's a narrowband source.
>>>
>>> I was merely saying that CO2 is a significant absorber and radiator
>>> at
>>> 210 K.
>>
>>OK, that I will buy.
>
> - Don Klipstein (don(a)misty.com)

From: Bill Ward on 22 Dec 2008 13:36
On Mon, 22 Dec 2008 13:51:19 +0000, Don Klipstein wrote:

> In article <pan.2008.12.15.05.10.44.858752(a)REMOVETHISix.netcom.com>, Bill
> Ward wrote:
>>On Mon, 15 Dec 2008 01:11:16 +0000, Don Klipstein wrote:
>>
>>> In article <pan.2008.12.07.07.55.55.626493(a)REMOVETHISix.netcom.com>,
>>> Bill Ward wrote:
>>>
>>>>On Sun, 07 Dec 2008 05:45:26 +0000, Don Klipstein wrote:
>>>>
>>>>> In article <pan.2008.11.29.05.49.04.133668(a)REMOVETHISix.netcom.com>,
>>>>> Bill Ward wrote:
>
>>>>>>He may also be aware that increased water vapor lowers the
>>>>>>condensation altitude,
>>>>>
>>>>> Cloud bases lower if relative humidity rises. Relative humidity
>>>>> stays
>>>>> about the same if water vapor concentration is only commensurate with
>>>>> temperature rise.
>>>>
>>>>Interesting concept. I'm assuming the surface temperature determines
>>>>the absolute humidity, and the condensation altitude would be
>>>>determined by the lapse rate downward from the cloud tops (radiation
>>>>layer). It seems to me the surface temperature varies a lot more than
>>>>the higher altitudes.
>>>
>>> It sure does! In fact, at the pressure level of most of the tropical
>>> tropopause (around or a little over 100 mb), on average it is cooler
>>> over the equator than over the poles!
>>>
>>>>Is there any actual data on the altitude of the radiation layer that
>>>>radiates the most power? From what I've seen, it's mid troposphere, not
>>>>the tropopause. Are there any credible models of the individual
>>>>mechanisms from cloud tops to the tropopause?
>>>
>>> That I know much less about. However, over the range of wavelengths
>>> at
>>> which the surface produces a lot of thermal IR, the transparency of the
>>> atmosphere varies greatly.
>>
>>My thought is that it wouldn't take much of an increase of temperature by
>>lowering cloud tops (assuming the same cloud thickness) below relatively
>>dry air, to radiate quite a bit more power through the tropopause. It
>>seems to me this information should be available from satellite images,
>>but I haven't seen it mentioned.
>
> It does appear to me that clouds lower than the tops of tropical
> thunderstorms do radiate more then the tops of tropical thunderstorms do.
> The tops of tropical thunderstorms are very cold.
>
> That gets complicated by how much GHG is over lower clouds.

Well, there is the WV hole at 10u, so most IR should get through.

> Meanwhile, addition of GHGs would be expected to make thunderstorms
> slightly taller and their tops colder.
>
>>>>>> raising the radiation temperature, and increasing the emitted IR
>>>>>>energy by the 4th power radiation law. IOW, it's a negative
>>>>>>feedback, not positive.
>>>>>
>>>>> Radiation from cloud bases is toward Earth.
>>>>
>>>>I think that concept confuses people, at least me, when I first heard
>>>>it.
>>>> It appears at first glance you are claiming the cloud bases are
>>>> warming
>>>>the surface, which is clearly impossible by the second law. The clouds
>>>>are colder than the surface, and energy can never radiate from cold to
>>>>hot.
>>>
>>> Cloud bases slow cooling of the surface in the usual case of cloud
>>> bases
>>> being cooler than the surface. There is radiation from surface to
>>> cloud base and radiation from cloud base to surface. The latter is
>>> less in the usual case of cloud base being cooler than surface, but
>>> that does subtract from net radiation from the surface.
>>
>>There's an example of a confusing statement. To me, the net surface
>>radiation is the outgoing surface radiation minus the incoming radiation
>>from the cloud base. Subtracting the cloud base radiation from the net
>>radiation seems to me like double counting it, or an unusual use of the
>>word "net". Was that a typo, or is it something you can explain?
>
> My explanation is that I am counting once - net radiation from the
> surface is radiation from surface minus what surface receives from cloud.
> That is less under clouds than under clear atmosphere.

That much I agree on. The net is the difference between the outgoing and
incoming. The next sentence is the one that confuses me: "The latter is
less in the usual case of cloud base being cooler than surface, but that
does subtract from net radiation from the surface."

Didn't you subtract it once already to get the "net radiation" in the
first place? It sounds like you are subtracting it again from the net
radiation, but I don't think that's what you meant.

>>>>A little more thought reveals the actual mechanism must be that some
>>>>of the radiation that comes from the surface can be considered to be
>>>>radiated back to maintain the (Tsource^4 - Ttarget^4) term in the
>>>>Stefan-Boltzmann equation. That still requires that the net heat flow
>>>>is outward, never inward (unless the surface is cooler). The upper
>>>>layers may reduce the cooling rate of the surface, but they can never
>>>>actually heat it.
>>>>
>>>>The _net_ radiation has to be from the surface to the clouds.
>>>
>>> It is. And since clouds emit some radiation towards the surface,
>>> and
>>> emit more radiation towards the surface than clear air does, they slow
>>> radiational cooling of the surface.
>>
>>Right. It slows the cooling, but the surface never increases its
>>temperature by radiation from a colder source.
>
> The surface is still warmer than without that downward radiation by
> cooling less.
>
>>>>> Meanwhile, increasing GHGs cools the lower stratosphere and raises
>>>>> the tropopause - cloud tops around the tropopause will be cooler.
>>>>
>>>>I'm not clear why. Could you explain why a cooler stratosphere raises
>>>>the tropopause? Is it because the tropopause is the top of
>>>>convection, so a colder stratosphere allows convection to continue
>>>>higher before the UV-O2, O3 inversion takes over?
>>>>
>>>>Thanks for your comments.
>>>
>>> The tropopause is generally the top of convection - although there
>>> is
>>> not convection under it everywhere. If the stratosphere is cooler,
>>> then the convection can go higher.
>>>
>>> The tropopause is highest in the tropics. Global circulation has
>>> air
>>> over the equator generally moving upward, since tropospheric
>>> temperature overall is warmest there.
>>
>>Wouldn't the tropical air moving upward be humid, and carrying a lot of
>>latent heat?
>
> It does. However, the tops of tropical thunderstorms are not much
> warmer than that level of the atmosphere outside them - in fact they are
> slightly cooler than most of the world's atmosphere at the same altitude
> and at the same pressure level.
>
> The latent heat would make a temperature difference when the air comes
> back down - since it would want to warm at the dry adiabatic lapse rate
> on the way down, while having cooled at the wet adiabatic lapse rate on
> the way up.
>
> As soon as cloudy air experiences much cooling by radiation, it
> descends, warms from adiabatic compression and clears. With most of the
> moisture rained out or snowed out before it has spent more than a few
> minutes near the tropopause, it does not have to descend much to clear.

And there's where the latent heat was deposited. The actual net latent
heat transferred would be the difference in the amount of water vapor
between the wet ascending and dryer descending air.
>
> (Some air in thunderstorms does descend more quickly, with precipitation
> in it.)

Won't some of that entrained precipitation evaporate when it reaches
warmer air, then repeat the condensation process in an updraft?

That's my beef with the Trenberth energy budget cartoon - he estimates
latent heat transfer from total global precipitation to the surface, which
is an absolute lower limit. There's a lot of water in all three phases
bouncing around inside thunderstorms, going both up and down at impressive
speeds. The net energy transfer has to be upward, and big.

Do you have any quantitative estimates on the recirculation of water in
thunderstorms? Like how many cycles on the average, or how much energy is
transferred per kg of water before it falls out of play?

> Then it has to be cooled by radiation as it descends while it is
> descending.
>
> Ability of clear air to radiate so that middle troposphere does not
> get much warmer outside of thunderheads than within them is necessary
> for them to keep on forming, or to form the next day.

I'd think there should be enough WV around to handle that. Clouds aren't
the only source of radiation.

> Some of the air rising in the ITCZ does not even descend locally - it
> descends in other parts of the world, as part of global atmospheric
> circulation.
>
>>> Where the upward motion actually exists and it does get localized to
>>> the hotspots where air rises most easily, the lapse rate makes a
>>> close
>>> approximation of the dry adiabatic one from the surface to the cloud
>>> base, and the wet adiabatic one from the cloud base to the cloud tops
>>> at the tropical tropopause.
>>> The tropical deep convection is in part forced by global
>>> circulation,
>>> and in part (especially on a local scale) natural convection from
>>> where the surface is warmer than elsewhere nearby. On a local scale,
>>> there is both updraft and downdraft, though in the intertropical
>>> convergence zone net air motion is upward.
>>
>>If warm wet air is going up, and cold, dry air is going down, the "net"
>>air motion would seem to be somewhat irrelevant, compared to the latent
>>heat transfer represented by up- and down-drafts in the convection
>>cells.
>> Do you think climate models simulate that correctly? I'm thinking of
>>Trenberth's assumption that latent heat transfer can be accurately
>>estimated by from global precipitation estimates. How do we know some
>>of the falling condensate isn't evaporated again before it hits the
>>surface?
>> It wouldn't take much to counter 1.5W/m^2.
>
> The bigger problem is increase of GHGs warming parts of the world that
> can be more easily warmed than tropics. Especially the portions of the
> polar regions where snow/ice cover changes when long term temperature
> changes - that is a positive feedback. Increase of water vapor is a
> positive feedback.

Doesn't that require the assumption that radiative transport is
more effective than convective transport?

> Reduced ability of oceans to hold CO2 when they warm
> is a positive feedback. Most of the surface level troposphere there can
> warm plenty before convecting. The main negative feedback of warming
> specific to higher latitudes is that making the surface temperature more
> even will reduce the global circulation transferring heat from the
> topics to the more extreme latitudes.

Won't that keep the heat at higher tropical temperatures, where it can
radiate more effectively due to the T^4 term?


From: Bill Ward on 22 Dec 2008 14:00
On Mon, 22 Dec 2008 14:22:58 +0000, Don Klipstein wrote:

> In article <pan.2008.12.18.06.59.46.603610(a)REMOVETHISix.netcom.com>, Bill
> Ward wrote in part:
>>On Thu, 18 Dec 2008 03:27:28 +0000, Don Klipstein wrote:
>>
>>> In article <pan.2008.12.09.15.55.30.33517(a)REMOVETHISix.netcom.com>,
>>> Bill Ward wrote:
>>>>On Tue, 09 Dec 2008 06:03:54 +0000, Don Klipstein wrote:
>>>>
>>>>> In <pan.2008.12.02.00.19.03.512271(a)REMOVETHISix.netcom.com>, Bill
>>>>> Ward wrote:
>>>>>>On Mon, 01 Dec 2008 08:59:25 +0000, Don Klipstein wrote:
>>>>>>
>>>>>>> In <pan.2008.11.29.04.28.21.555150(a)REMOVETHISix.netcom.com>, Bill
>>>>>>> Ward said:
>
>>>>>>>>Energy is conserved. Where did the latent heat go, if not up?
>>>>>>>>It's carried by convection to the cloud top, and radiates away.
>>>>>>>
>>>>>>> Not all of it (latent or the majority otherwise) does.
>>>>>>
>>>>>>Then I repeat: Where did it go? Surely you're not claiming net
>>>>>>energy is moving from cold air to warm surface. The second law cops
>>>>>>will come and get you.
>>>>>
>>>>> Some gets radiated. Much ends up on surface farther from the
>>>>> tropics
>>>>> than where it came from. A little bit does end up on surface hotter
>>>>> than where it came from (in dry subtropical highs), but that is
>>>>> clearly greatly a minority.
>>>>
>>>>That would require a heat pump. Could you explain the mechanism?
>>>
>>> Global atmospheric circulation driven by troposphere being warmer in
>>> the
>>> tropics than around the poles but on a rotating planet gives us such
>>> things as the subtropical jetstreams and subtropical highs.
>>>
>>> The heatpump results,
>>
>>I was thinking more of an explanation of the physics involved in moving
>>heat from a cool spot to a hotter one. Like what the working fluid is,
>>and where the stages of the cycle take place.
>>
>>> and does indeed have a minority of the air ascending in the ITCZ
>>> descending to the surface outside the ITCZ hotter than cooler. From
>>> surface to roughly the 110 mb level, the average temperature is
>>> supposed to be colder where the air descends. The descending air could
>>> cool by radiation - when descended to levels of the atmosphere with
>>> below-avererage GHG overhead (due to being very dry). Extra heating at
>>> some altitudes (sometimes close to surface) results from descent
>>> warming at the greater dry adiabatic lapse rate except for such air
>>> cooling radiationally from its GHGs - which it has less of (due to
>>> being dry), though it has below-average extent of GHG overhead. The air
>>> in hotspots of subtropical highs could even get pushed down by local
>>> weather features, though when "that hot" has to be a small minority in
>>> order for the laws of thermodynamics to hold true.
>>>
>>> Meanwhile, the highest temperatures in Africa and in North America,
>>> also
>>> above sea level in North America, are quite far from the equator - I
>>> would dare say at least 27 degrees north latitude, maybe more like
>>> closer to 30.
>>>
>>>>>>> And greenhouse gases above the cloudtop will return to the cloud
>>>>>>> some of the cloud's thermal radiation.
>>>>>>
>>>>>>Not net radiation. The net energy flow is always from hot to cold.
>>>>>>Always.
>>>>>
>>>>> GHGs will add impedance to that flow.
>>>>
>>>>And latent heat transport will decrease the impedance.
>>>
>>> And increase thereof will decrease temperature difference between
>>> where
>>> the heat comes from and where the heat goes. Much of the air rising in
>>> "tropical deep convection" descends elsewhere in the world,
>>
>>Once the water vapor has been lifted and condensed, the latent heat has
>>been transferred. How can it be transferred downward? First the air has
>>to cool so it can sink. Is there any way other than radiation?
>
> It does radiate. And since sinking air tends to be clear, it has to do
> a lot of its radiation while clear in order to sink.
>
> The tops of tropical thunderstorms are at about the same temperature as
> the surrounding clear air at the same level. The lapse rate from cloud
> top level to cloud base level is close to the wet adiabatic one, and air
> tries to warm at the rate of the dry adiabatic one as it sinks. Radiation
> allows it to descend, mostly while it is descending.

Through relatively warmer air, increasing the T^4 term.

> The radiation is often little enough for thunderstorms to warm most
> levels of the nearby troposphere with descending clear air. Limited
> ability of that air to sink limits the number of thunderstorms.

Isn't that an example of negative feedback? When enough energy has been
lifted to result in a stable lapse rate, the cooling stops. That
stabilizes the temperature.

> Some of the air rising through tropical thunderstorms does not even
> descend locally, but elsewhere in the world - still doing so gradually
> as radiational cooling allows it to descend.

Why would it matter where or when it radiates the heat? The surface has
been cooled by evaporation, and the energy has no way to go but up.

>>> since rising
>>> air in "tropical deep convection" is part of global atmospheric
>>> circulation. Global atmospheric circulation already contributes to
>>> the polar regions being warmer and the tropics being cooler than they
>>> otherwise would be. (Global oceanic circulation also does that -
>>> reduced exposure to global oceanic circulation makes the Red Sea and
>>> nearby areas hotter than otherwise-similar tropical areas.)
>>
>>Is it really that, or the fact that it gets a lot of sun and not much
>>cloud cover?
>
> That's probably part of the explanation also. However, I seem to
> think
> that there are other tropical areas with similar amounts of sunlight and
> cloud cover that don't get as warm.
>
>> Slowing the cooling rate is not heating.
>
> That still makes something warmer than it otherwise would be.

Only if it's being heated by something else.

>>>>>>>> The whole notion of somehow "trapping" energy in the atmosphere
>>>>>>>> seems ludicrous. It's either sensible heat, latent heat, or
>>>>>>>> radiation. It doesn't just disappear.
>>>>>>>
>>>>>>> It accumulates until radiator temperatures get sufficient to have
>>>>>>> radiative outgo to outer space match radiative income from the
>>>>>>> Sun.
>>>>
>>>>If by "accumulating", you mean the temperature increases, yes. The
>>>>radiation is proportion to the 4th power of that temperature.
>>>>
>>>>>>Then it's sensible heat subject to upward convection.
>>>>>
>>>>> It won't convect much until warming achieves lapse rate achieving
>>>>> the relevant adiabatic one.
>>>>
>>>>And accumulating heat will raise the temperature until convection
>>>>begins.
>>>>
>>>>> Most of the atmosphere has lapse rate less than the relevant
>>>>> adiabatic one.
>>>>
>>>>Probably. Half of the atmosphere is in nighttime. Wouldn't you agree
>>>>most heat is transported to the radiative layer during the daytime,
>>>>when temperatures are higher?
>>>
>>> I would agree much more heat gets transported there during daytime
>>> than at nighttime.
>>>
>>> However, most of the world lacks cloud tops within 4 km of the 350
>>> mb
>>> level, and a lot of the air gettinmg that high or higher manages to
>>> not lose a lot of heat by radiation before it descends - a lot of
>>> radiational cooling of air occurs where its descent requires cooling
>>> as it descends (One good example is polar vortices).
>>
>>Cooling doesn't have to take place equally all over the globe. Of
>>course some areas will cool less effectively than others. Shouldn't the
>>emphasis be on understanding the most effective mechanisms, rather than
>>focusing on places that don't play much of a part?
>
> Cooling is still significant in parts of the globe where it is less.
> And those happen to be parts of the world where there is little
> convection, and some of those have the positive feedback mechanism of
> variation of snow and ice cover with temperature.

It's a matter of degree. We seem to agree that most of the cooling occurs
in the tropics, and the quantitative importance of the poles still seems
to be uncertain, especially if you can see negative feedback at work in
the convection mechanism. The polar regions just seem kind of dull and
thus easier to model.

>
>>>>>> The temperature is a function of the gas laws and the specific heat
>>>>>> of the air. Warming a parcel of gas doesn't "trap" any radiation.
>>>>>
>>>>> I did not say warming a parcel of gas makes it trap radiation.
>>>>> What I
>>>>> said was that if a parcel of gas was cooler than achieving radiation
>>>>> balance, it will warm from radiation.
>>>>
>>>>True. That warming assists convection.
>>>
>>> What if it warmed where the lapse rate was short of allowing
>>> convection? That describes at least 80% of the troposphere!
>>
>>What if the 20% where it does happen is enough? There seems to be
>>general agreement that climate models don't handle deep tropical
>>convection all that well. Yet that's where most of the cooling happens.
>>It wouldn't take much negative feedback to wipe out the estimated CO2
>>forcing.
>
> Except that tropical deep convection only cools the tropics. It does
> not cool the polar regions.

When I look at the globe, I see a lot more tropical region than polar
region.

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