I’ve marked Figure 3 to show the dead zone here .

What I wonder is whether this dead zone can be “put to work” radiating away heat in an AGW world. Maybe this is already expected and is captured by the GCMs, or maybe my understanding is wildly wrong and there is no dead zone – dunno. I’m simply playing with an idea.

How would the dead zone be put to work? One obvious possibility is that a generally warming tropical troposphere should also warm the dead zone, and when the dead zone warms it overcomes that odd property of water molecules and begins to radiate IR to outer space.

A second possibility involves the Hadley-Walker circulation. A grossly simplified schematic of the circulation is here , with the normal free troposphere radiative zone shown in purple. This is a clear-air zone (say, eastern Pacific) where the convective outflow
radiatively cools and sinks.

In an AGW world the purple zone becomes sluggish in removing IR, due to the presence of extra CO2 and water vapor, which is shown here .

In this scenario the convective outflow may tend to rise over the “obstacle” of the sluggishly-cooled air in the purple zone. The outflow enters the dead zone but, unlike the normal dead zone air, this parcel is warm enough to radiate IR, (see here ). Thus the tropospheric radiating region expands, acting as negative feedback to AGW warming.

Now, there are energy considerations in getting air to rise (“no free lunch”) and other issues which complicate things. But, perhaps some variation of “putting the dead zone to work” is plausible. Dunno.

Fu, R., Y. Hu, J.S. Wright, J.H. Jiang, R.E. Dickinson, M. Chen, M. Filipiak, W.G. Read, J.W. Waters, and D.L. Wu, “Short circuit of water vapor and polluted air to the global stratosphere by convective transport over the Tibetan Plateau” Proc. Nat. Acad. Sci. 103, 5664-5669, 2006. reprint (PDF)

From the abstract:

During boreal summer, much of the water vapor and CO entering the global tropical stratosphere is transported over the Asian monsoon/Tibetan Plateau (TP) region.

[...]

Tropospheric moist convection driven by elevated surface heating over the TP is deeper and detrains more water vapor, CO, and ice at the tropopause than over the monsoon area. Warmer tropopause temperatures and slower-falling, smaller cirrus cloud particles in less saturated ambient air at the tropopause also allow more water vapor to travel into the lower stratosphere over the TP, effectively short-circuiting the slower ascent of water vapor across the cold tropical tropopause over the monsoon area. Air that is high in water vapor and CO over the Asian monsoon
TP region enters the lower stratosphere primarily over the TP, and it is then transported toward the Asian monsoon area and disperses into the large-scale upward motion of the global stratospheric circulation.

From the discussion:

Evidently, the hydration of the global stratosphere could be especially sensitive to natural and human-induced climate change over the TP, especially the observed warming of surface temperatures.

This is the first peer-reviewed article I’ve found that mentions something I read about a long time ago: the very high east-to-west jet stream over the Himalayas during the northern hemisphere summer. It isn’t mentioned explicitly, but the southern boundary of “a strong anticyclonic circulation over the TP” would be just that.

I suspect that Qclr represents the very top of the Hadley-Walker cell, with the air above it being part of the lower stratospheric activity. Given that the temp is falling when the air rises, I wonder if this is the normal source of stratospheric cirrus.

I wish there was more research on what these areas look like between, say, 20-50 degrees latitude.

And, it seems like lapse rate in this region (a downleg of the Hadley-Walker cell) is quite important, as the planet sheds considerable IR there.

This image for a downleg of the Hadley-Walker cell introduces several ideas. One is that the point of radiative clear-air balance (Q) is a couple of km below the lapse-rate tropopause (region of minimum temperature). Above the Q layer tropospheric air may warm and rise while below that the air cools and sinks.

The location of Q if fairly constant in terms of potential temperature (potential temperature is the temperature of a parcel of air subjected to 1000mb pressure (“a parcel transported to sea level”)).

The main convective outflow is below Q by several km, except for thunderstorms that overshoot.

The location of Q varies by 1 to 1.5km between day and night. It’s also a function of ait temperature and water vapor.

The temperature profile is here (blue line).

Basil,

MSU refers to Microwave Sounding Units. Both Remote Sensing Systems and University of Alabama Huntsville take raw intensity data from the the satellite MSU’s and convert them to temperatures at different altitudes. I assume you meant to say you used the UAH MSU data as opposed to the RSS MSU data. If RSS does indeed overcorrect, then trends in either direction will be amplified compared to UAH. Time will tell.

I missed the return of Pielke, Sr.’s blog. Nice to know he’s back.

On the other hand, maybe ozone/water vapor ratio of less than +/- 90/10

Or pick a temperature curve in the area between troposphere and stratosphere.

Just a common frame of reference.

Thanks, jae. I’ve already referenced that paper in posts on other threads.

The zone of no heating and the cold point are actually different things, although usually within a Km or so of each other. That was part of the point of my post on the “From Lacis et al 1981 to Archer Modtran” thread. They’re examining the relationship between these two points, as well as the Lapse Rate Minimum. IMO trying to insist on a single thin sheet as the “tropopause” is misleading because the processes going on in the TTL are dependent on the relationship between these points.

Not to mention that the TTL can be as much as 5Km thick at times/places, which compares well the the troposphere.