Stratospheric Temperature & CO2

[BornFromTheVoid]

CO2 contributes towards a cooling of the stratosphere, and it's trend of -0.37C/decade. With last year being the coolest global stratosphere year on record according to RSS (3rd coolest with UAH), were probably seeing those cool temperatures spilling over into 2013.

NCDC Upper Air 2012 Report

Edited February 1, 2013 by BornFromTheVoid

[Paul]

The above post has been split out from the main strat thread as it merits a separate discussion within the climate forums

[knocker]

that link doesn't seem to work for me for some reason.

[BornFromTheVoid]

that link doesn't seem to work for me for some reason.

How about now?

[knocker]

Cheers BFTV. Just a quick observation but continued cooling should lead to more ozone depletion with the formation of more PSCs. Having said that they are somewhat complex and we do not yet fully understand the mechanism for PSC freezing, and this remains one of the largest uncertainties in stratospheric ozone modelling.

http://www.atm.ch.cam.ac.uk/tour/psc.html

[Gray-Wolf]

For simpletons like me , does a cooler strat lead to a warmer Trop?

[BornFromTheVoid]

For simpletons like me , does a cooler strat lead to a warmer Trop?

Kinda the other way around, depending on the mechanism. While the actual explanation is more complicated, it's basically that the longwave radiation is being trapped more at the surface (due to CO2), reducing the energy reaching the stratosphere. So we get warming of the trop and cooling of the strat.

More info here and here

Cooling due to the greenhouse effect

The second effect is more complicated. Greenhouse gases (CO2, O3, CFC) absorb infra-red radiation from the surface of the Earth and trap the heat in the troposphere. If this absorption is really strong, the greenhouse gas blocks most of the outgoing infra-red radiation close to the Earth's surface. This means that only a small amount of outgoing infra-red radiation reaches carbon dioxide in the upper troposphere and the lower stratosphere. On the other hand, carbon dioxide emits heat radiation, which is lost from the stratosphere into space. In the stratosphere, this emission of heat becomes larger than the energy received from below by absorption and, as a result, there is a net energy loss from the stratosphere and a resulting cooling. Other greenhouse gases, such as ozone and chlorofluorocarbons (CFC's), have a weaker impact because their concentrations in the troposphere are smaller. They do not entirely block the whole radiation in their wavelength regime so some reaches the stratosphere where it can be absorbed and, as a consequence, heat this region of the atmosphere.

[pottyprof]

While the actual explanation is more complicated, it's basically that the longwave radiation is being trapped more at the surface (due to CO2), reducing the energy reaching the stratosphere.

It's probably because of the meds at this time of day but I'm struggling to get my head around something. If increasing CO2 is trapping longwave radiation, shouldn't the out going energy also increase eventually, given that CO2 radiates this energy in all directions equally? Is there something else preventing this exchange to the stratosphere from happening? I would have thought CO2 in the troposphere was fairly mixed through by air movement?

Genuine questions for a complicated subject btw.

Edit. Just reread the links and it sort of went in. I'll try again later..

Edited February 2, 2013 by pottyprof

[full_frontal_occlusion]

If increasing CO2 is trapping longwave radiation, shouldn't the out going energy also increase eventually, given that CO2 radiates this energy in all directions equally? Is there something else preventing this exchange to the stratosphere from happening? I would have thought CO2 in the troposphere was fairly mixed through by air movement?

Genuine questions for a complicated subject btw.

Energy conservation laws dear chap.

Longwave radiation carries less energy than the incoming shortwave per quanta. So less energy gets back out into space and the temperature on the inside (atmosphere beneath the CO2 layer) rises as more energy gets stored. But as the stored energy increases, the amount of energy lost through longwave radiation back out into space also starts to increase - until the incoming/outgoing balance is restored and the temperature reaches equilibrium in the troposphere.

The stratosphere is transparent to longwave to all intent, so energy transfer is via convection between layers.

ffO.

Edited February 2, 2013 by full_frontal_occlusion

[pottyprof]

Energy conservation laws dear chap.

Longwave radiation carries less energy than the incoming shortwave per quanta. So less energy gets back out into space and the temperature on the inside (atmosphere beneath the CO2 layer) rises as more energy gets stored. But as the stored energy increases, the amount of energy lost through longwave radiation back out into space also starts to increase - until the incoming/outgoing balance is restored and the temperature reaches equilibrium in the troposphere.

The stratosphere is transparent to longwave to all intent, so energy transfer is via convection between layers.

ffO.

Thanks FFO. I think that is what I'm trying to work out, what's happening at the boundaries?

[full_frontal_occlusion]

Thanks FFO. I think that is what I'm trying to work out, what's happening at the boundaries?

Oh, just noticed this reply so apologies for the belated response:

I'm no expert, so some of the others may wish to interject

The boundary is defined by a thermal inversion which as you know varies with height between the polar regions and at the equator. As far as is practicable, there is very little mixing between the stratosphere and troposphere.

The coupling between the layers therefore arises from adiabatic expansion and contraction of regions of air within each layer. The gas laws (PV/T = constant) which themselves are a function of the thermodynamic conservation laws, which state that as the temperature within a gas rises (forced by external influence), then either the pressure or volume or both must change in order to ensure equilibrium.

This means that if the temperature of a region within the stratosphere rises then the pressure and volume of the gas within that region must also change (divergence). This will therefore influence the tropospheric air underneath causing low level convergence. Thus adiabatic (or diabatic) expansion and contraction corresponds to tropospheric air pressure changes together with a thermal change.

NB. Little work is done between the layers so there is no net exchange of energy between them. The surface thermal and pressure changes are a result of the expanding and contracting of pressure coupling between the layers.

Does that make more sense?

ffO.

[pottyprof]

Does that make more sense?

ffO.

Very much so. Thanks.

[Harve]

Is it that warming on the earth's surface is countered by cooling in the stratosphere or is one more dominant than the other? Obviously, surface temperatures are what directly affects life, but it's interesting to see what exactly is happening to the Earth's energy budget.

Edited February 11, 2013 by Harve

[Gray-Wolf]

I think the easiest way to see if the planet is balanced or not is to look at temp trends? If the energy in equals the energy out then we are 'balanced and temps remain stable. If we hold onto more energy than we shed then things warm.

The ocean temps (our biggest heat sink) have seen a 0.2c rise in temps in their upper layers over the past 20yrs. It looks like we are still out of kilter?

As for the 'boundary layers' I've read , over the years, that this boundary is increasingly breached by more intense thunderstorms punching through into the strat (and introducing more water vapour there?). I remember the storm that brought us Boscastle punched well into the strat?

What does extra H2O do to the strat if this phenomena is occurring?

[full_frontal_occlusion]

Is it that warming on the earth's surface is countered by cooling in the stratosphere or is one more dominant than the other? Obviously, surface temperatures are what directly affects life, but it's interesting to see what exactly is happening to the Earth's energy budget.

The simple answer is no, surface warming is not countered by stratospheric cooling.

As the planets surface heats up due to absorption of shortwave UV radiation from the sun, the release of that stored surface energy is via longwave infra-red radiation. It's here that greenhouse gases trap that energy and the troposphere heats up. However as the net global tropospheric temperature increases (and since the rate of radiation is also a function of temperature), the troposphere emits radiation at a higher rate, an ever increasing part if which then goes straight past the stratosphere and exits to space.

The tropospheric temperature can only equalise and remain constant when the incoming shortwave energy absorbed is equal to the longwave outgoing radiated energy. i.e. the energies are balanced.

ffO.