Tropical and Arctic Tropopause

Hans Erren observes:
one other serious complication exists in the real world which we shouldn’t overlook. There are two stable tropopause heights observed in the atmosphere:
Tropical tropopause
Arctic tropopause

At their boundaries (mid lattitude) the most intersting weather occurs, where most people live and where climate change affects the most people. What will happen with increased CO2, will the tropcal troposphere move northwards, will the interaction beteen arctic and tropica tropopause become more or less active?

lots of guessing and scaremongering is happening.

tropopause profile
tropopause height

tropopause maps
north pole view

David Smith observes:
The 1970s climate regime shift included a tropical tropopause temperature shift . The pattern is similar, but of a smaller magnitude, in the extratropical tropics.

This is based on NCEP reanalysis data.

I offer no conjecture as to why this apparent shift happened. The pressure-height of the tropical tropopause did not shift at the same time, which adds to this little puzzle.


  1. AK
    Posted Jan 11, 2008 at 11:55 AM | Permalink

    Sheer speculation here: The current turbulent system in the atmosphere represents a “stable” configuration. There may be other such configurations, also somewhat “stable”. The shift in the ’70’s may represent a transition from one “stable” configuration to another.

    In terms of chaos theory, these would be separate attractors, with the annual weather pattern shifting from one to another due to some “perturbation”, either internal or external.

  2. Peter D. Tillman
    Posted Jan 11, 2008 at 11:59 AM | Permalink

    Steve (or whoever), is there a tutorial on the blog somewhere on posting gifs/jpgs here?

    If so, I’ll post it over at (and use it myself ;-))…

    TIA, PT

  3. SteveSadlov
    Posted Jan 11, 2008 at 12:05 PM | Permalink

    So called “space weather” and mechanical forces constrain the max height of the ionosphere – exosphere boundary. This is but one wrinkle in the “expanding atmosphere” paradigm. Certainly, expansion of the troposphere cannot be completely ruled out, but beyond that, no one knows. And therefore, we turn to velocity.

  4. Posted Jan 11, 2008 at 12:06 PM | Permalink

    It is pretty clear that the jump from 1979-1980 in the NCEP-reanalysis is due to the inclusion of satellite data.

  5. John Lang
    Posted Jan 11, 2008 at 12:10 PM | Permalink

    The excellent website of the Tropopause linked to by Hans Erren, has an “animate” function showing the past 10 days. It looks like an extremely chaotic system to me.

  6. Sam Urbinto
    Posted Jan 11, 2008 at 12:25 PM | Permalink

    My take is that almost everything we see in the global mean temperature anomaly trend is due to the changes in measurements since the late 1970’s. Of course, I can’t prove that any more than anyone else can prove it’s due to lag….

    As far as two tropopauses, it’s more like 2-5 of them in a way. And the tropical injection of CH4 into the stratosphere is what results in the creating of the positive forcing water vapor (among other things.)

    Great stuff Hans!

  7. Michael Jankowski
    Posted Jan 11, 2008 at 12:27 PM | Permalink


    Possible, but what explains the trend back to pre-satellite data levels?

  8. Sam Urbinto
    Posted Jan 11, 2008 at 12:38 PM | Permalink

    Michael, that’s just it, the ground/sea anomaly trend is about +.5 C for the last 30 years; almost all the trend is since the late 1970s.

    If you just take the trend Jan 1978 to Dec 2006 for ground, it’s +.8 just by itself.

    Combining land and sea gives -.3 C compared to just land. Something’s going on. Anyone have a similar link to the 1978-2006 satellite anomaly for air to compare to ground-based air temp anomaly?? (Something short)

  9. Posted Jan 11, 2008 at 1:11 PM | Permalink

    Re #4 Thanks Ryan for the observation. That could be the case though, while satellite data is good for detecting the temperature change in broad and overlapping sections of the atmosphere, I didn’t know it is good enough to detect the absolute temperature of a small part of the atmosphere. Perhaps the satellite data gets involved indirectly.

    I’ll check the behavior of adjacent layers and report.

  10. Tim Ball
    Posted Jan 11, 2008 at 1:46 PM | Permalink

    My goodness. Climate science discovers sophisticated statistical techniques. For years climate science dealt only with averages then the post 1940 cooling triggered a spate of simple trend analysis with predictions of another Ice Age . Now they are learning about variability. The variability in weather variables and thus climate is much greater than allowed and a significant measure of changes, especially in conjunction with the shift form zonal to meridional flow, reversals of the tropical easterlies, ENSO, PDO and all other oscillating climate drivers. It is the problem I have with the data lost in smoothing techniques to achieve a simple trend analysis. The ice cores are a good example.

    As an aside, it appears variability of mid–latitude weather increases with global warming and reduces with a cooling trend. You can eyeball this general pattern with the graph of temperatures for the continental US, the best represented area for quantity and quality of data ( I know that isn’t saying much but…)

  11. SteveSadlov
    Posted Jan 11, 2008 at 1:46 PM | Permalink

    Since the 1998 El Nino, here at the upper 30s N, West Coast NoAM, “pineapple express” and other strong warm advection type events have been pretty few and far between. There has, instead, been a notable bias toward inside slider, Siberia Express, and other polar oriented systems. I wonder how that jibes with the “the Ferrel Cell’s southern limit is moving poleward” meme?

  12. Patrick M.
    Posted Jan 11, 2008 at 1:50 PM | Permalink

    Is this shift linked to the major PDO phase change of 1976-1977?

  13. novoburgo
    Posted Jan 11, 2008 at 2:05 PM | Permalink

    To solve the mystery of “The Missing Typical Tropical Tropopause” we may need to call on “Captain Vorticity and his girlfriend “Divergence!”

    Sorry…couldn’t help myself, been waiting years for someone to start talking tropopause.

  14. Posted Jan 11, 2008 at 2:29 PM | Permalink

    The NCEP reanalysis is a 3D Var numerical weather prediction model (just like a climate model) except that it ingests, assimilates, and updates (cycles) every 6 hours as new obs are available. During the 1970s, the radiosondes in the tropics were sparsely populated. As satellite data became available in 1979, mainly temperature retrievals and radiances (for ERA40), questions about background errors and data homogeneity are still be addressed today.

    There are several papers by Santer and Pielke Sr. and Trenberth that address the tropical troposphere/tropopause temperature issues. There is little doubt that data problems are to blame.

  15. Basil Copeland
    Posted Jan 11, 2008 at 3:07 PM | Permalink

    Re #4, #7 and #10

    I’m likewise troubled by the tendency to plot simple trend lines through the satellite data. Using the MSU global land and sea series, the average seasonal first difference is 0.014, equivalent to a 0.14 “decadal” trend. But if we break this down into three periods, the first being 1978:12 through 1992:11, the second 1992:12 through 2002:11, and the last 2002:12 through 2007:11, the equivalent “decadal” trends are: -0.0641, 0.5025, and -0.0500. All the “trend” is coming from the decade 1993-2002.

  16. DeWitt Payne
    Posted Jan 11, 2008 at 4:03 PM | Permalink

    Re: #15

    Are you using RSS or UAH MSU data. The RSS LT global anomaly has been negative for the last two months and has dropped nearly 0.3 degrees in the last four months. The tropics (-20 to 20 latitude) is dropping even faster. Who said that we can’t have a super La Nina unless we first have a super El Nino?

  17. Sam Urbinto
    Posted Jan 11, 2008 at 4:31 PM | Permalink

    What troubles me is this versus this.

    Then, compare 1918 to 1929 to 1956
    Then, compare 1956 to 1964 to 1976

    Now, next question, what separates 1944 and 1980?

    The fact is that “the warming” doesn’t start getting higher than 1944 until 1980, and except for 1997-1998 and 2002-2006 there is nothing very abnormal in there. The majority of the trend is created by 1990, 1995, 1997, 1998 and 2001-2006. Those 10 years basically create the trend. (1990 and 1995 are no more odd numerically than, say, 1929 and 1950)

    Then consider the difference between a year like 1998 and 1990 — +.21 C Big deal — 1915 and 1916 are -.23 C There’s really nothing there.

    Now lets make it more interesting. How is the period of (basically) 1997-2006 in the positive any more strange than the period of 1903 to 1913 in the negative? In fact, 1903-1913 is more consitently cold more than 1997-2006 is consistently warm. Nice, hunh?

    (For the sake of argument, I’m considering the global mean temperature anomaly trend reflects actual physical warming, even though that has not been proven or disproven at this point in time.)

    One last thing; 2007 is in at + .57 (here ) and plotting that gives 1880-2007

    I must mention that this data set has different numbers than the top links to the GCAG at NCDC do, even though they are supposed to be the same ghcn-ersst as far as I can tell.

    ———-2001 2002 2003 2004 2005 2006 2007
    GCAG:——+.4 +.45 +.47 +.44 +.51
    GISSTEMP:-+.48 +.56 +.55 +.49 +.62 +.54 +.57

    Charting the GISSTEMP gives a linear trend since 1880 of +.68 and since 1980 of +.47

    Fun with numbers, indeed. Will the real GMTA trend please stand up?

  18. Sam Urbinto
    Posted Jan 11, 2008 at 4:35 PM | Permalink

    Stupid formatting.

    GISSTEMP in text file
    2000 .33
    2001 .48
    2002 .56
    2003 .55
    2004 .49
    2005 .62
    2006 .54
    2007 .57

    GCAG chart
    2000 .27
    2001 .40
    2002 .45
    2003 .47
    2004 .44
    2005 .51

  19. anonymous
    Posted Jan 11, 2008 at 4:39 PM | Permalink

    Is it possible not to look at the huge spike after 1980 and not think “Mount St Helens” ?

  20. anonymous
    Posted Jan 11, 2008 at 4:42 PM | Permalink

    One too many not’s I guess.

  21. Posted Jan 11, 2008 at 5:24 PM | Permalink

    RE #14, #9 Thanks for the note, Ryan. I’ve been aware that the NCEP reanalysis is of dubious use for examining small changes, and has gaps due to poor input data (like upper-tropospheric water vapor data from radiosondes), but had thought that gross changes in key parameters over a large geographical area like air temperature would at least be directionally useful.

    If the computer model output is glaringly screwed up on something as basic as upper-air temperature in the 1970s, which likely affects many other atmospheric parameters in their model, then it’s hard to see how their time series of any parameter at any scale has any value. What a mess.

    Anyway, I plotted the NCEP temperature data for 200mb, 150mb, 100mb (approx tropopause) and 70mb, located here . The red tic marks are the earliest period that satellite data could have been incorporated. While there are temperature increases in 1978-79 in the upper tropical troposphere, the distinctive move is at the 100mb (approx tropopause) level. The 200mb and 70mb increases appear (to me) to be in-trend while the 100mb looks like a step-up. The 150mb is in-between.

    It’s not clear to me how a late-70s incorporation of satellite data would have such a notable impact on the tropical 100-150mb level but not on the adjacent levels.

    This matter is one where I’ll take the “dunno” position. I’m not quite ready to toss it out as an artifact.

    (Oh dear, I just realized I’m defending NOAA computer model outputs…I must have a fever.)

  22. tamborineman
    Posted Jan 11, 2008 at 5:47 PM | Permalink

    The weather pattern that existed in this part of the world from the 40s to the late 70s then disappeared and is only now showing signs of re-emerging.
    eg: No tropical cyclone has crossed our coastline [SE Queensland Aust.] since 1976 whereas we used to get up to 6 a year.

  23. Posted Jan 11, 2008 at 6:15 PM | Permalink

    Re #21 A slightly different presentation of the same data is here . The behavior of the 100mb (approx tropopause) level stands out.

    While I’m posting charts, this one from NOAA is interesting. (I may replot it onto a line chart later because the bar chart with the zero in the middle doesn’t do it justice.) The data is from radiosondes and is of the global free mid-troposphere.

    There appears to be a clear step-up in temperature in 1976-77, at the time of the PDO/ENSO shift. I imagine that the surface (oceans and land) take a bit longer to warm, due to the oceans’ heat capacity. It’s plausible that, as the surface responds, it may trigger other notable shifts in the free troposphere. A “climate regime restructuring” may take several years to play out. Conjecture.

  24. Posted Jan 11, 2008 at 7:33 PM | Permalink

    The NCEP reanalysis products (or any other reanalysis for that matter) are not used for temperature trend analysis for climate change detection and attribution except for Santer’s tropopause height changes (which use a lapse rate calculation). The article, comment by Pielke Sr. and reply to Science Mag 2003 Article will get you up to speed very quickly on the pitfalls with upper-tropospheric temperature reanalyses.

    When observations are not available, the reanalysis drifts towards the model background or its own climatology (as prior to 1979 when radiances were introduced). Thus, any bias in the model may then show up as an increasing trend when the new data is assimilated, yet nothing in reality has happened.

  25. Posted Jan 11, 2008 at 8:08 PM | Permalink

    Re: #17

    Some interesting observations. Let me provide one more.

    If, as some contend, the warming was “natural” prior to about 1956, consider the following: Look at the trend from about 1913 to about 1944. This warming was “natural.” If one extrapolates that trend to the early 21st Century, the recent (not sure it is still continuing) warming hasn’t quite caught up to the earlier trend line. So, which is “non-natural”? The current warming (which is below the earlier “natural” trend line) or the major cooling in the middle of the 20th Century?

  26. Andrew
    Posted Jan 11, 2008 at 9:27 PM | Permalink

    DeWitt Payne, you mention the current anomaly in the RSS but I’m fairly certain that UAH is more accurate. I can’t remember the reference for this, but I seem to recall that being the case.

    Correct me if I’m wrong, though.

    Mike Smith, you can’t assume natural linearity. That’s just not how it works. None of it has to be non-natural, and it is inappropriate and in accurate to simply use a linear trend to determine what can be “natural”.

  27. steven mosher
    Posted Jan 11, 2008 at 9:28 PM | Permalink

    re 19. mount st helens ash didnt get high enough. she blew out a side gasket

  28. Bugs
    Posted Jan 11, 2008 at 9:44 PM | Permalink

    Tim Ball

    you’re making it up.

  29. Posted Jan 11, 2008 at 9:49 PM | Permalink

    Re #24 Thanks for the links, Ryan – good reading and they indeed capsule the key points. I’ll put the reanalysis data into the “probable ca-ca” bin thought the different behavior of the 100mb level does make me pause.

    If you know of any studies which present tropical upper-troposphere temperature time series, please post.

    On a related topic, while looking for such data I came across an interesting article . A paragraph that intrigued me is

    An important, but
    under-appreciated aspect of clear-sky radiative cooling in the
    tropics is the steep drop to small values from 250mb to 150mb
    (14 km). The radiative relaxation time depends on the vertical
    scale of the temperature anomaly assumed in the calculation.
    Sinusoidal temperature anomalies with vertical wavelengths of 7
    and 14km were added to the climatological profile. The phase of
    the temperature anomaly was chosen so that the maximum
    anomaly of 1K occurred at the level of interest. The temperature
    anomaly divided by heating rate anomaly at the level of interest
    gives an estimate of the relaxation time scale at that level for
    perturbations with the chosen vertical wavelength. A sharp
    increase of the radiative relaxation time is associated with the
    drop in net cooling rate near 200mb. Both of these changes occur
    because absorption and emission of longwave radiation by water
    vapor become ineffective at temperatures lower than that of the
    tropical atmosphere at about 150mb. It is interesting that this
    appears to be a fundamental property of water vapor emission
    tied to temperature, rather than a special property of the current
    climatology of the tropics on Earth. The cooling near 250mb
    comes mostly from strong emission from rotational lines of water
    vapor at wavelengths longer than about 35mm. This cooling cuts
    off abruptly near 200mb as the saturation vapor pressure falls
    exponentially with declining temperature

    along with this chart .

    This dropoff in radiative cooling, due to water vapor characteristics, was unknown to me – live and learn! This may play a key role in tropopause location. I’ve got to put this in my (figurative) pipe and smoke on it for awhile.

  30. deadwood
    Posted Jan 11, 2008 at 11:46 PM | Permalink


    The problem with invoking St, Helens is that it was in part, as Steve pointed out, a lateral blast. In addition, volcanic ash and aerosols would tend to cool rather than heat. And finally, it was a relatively small eruption with only about 1 billion tons of ash (say vs. Pinatubo with 10 billion or Krakatoa with 10 times that).

  31. Posted Jan 12, 2008 at 5:47 AM | Permalink

    I can’t get the image to display so here is the URL

    This is minor editing to a figure from the paper in the URL shown. I do not know how correct it is. If it is typical, then it indicates fair complexity in dividing a cartoon or model between above tropopause and below, since it might not be continuous and there could be lateral transport effects at the discontinuity. French work.

  32. Pat Keating
    Posted Jan 12, 2008 at 9:33 AM | Permalink

    31 Geoff

    Interesting figure. How do they define the tropopause? Pressure? Temperature (gradient)? Other?

  33. Peter D. Tillman
    Posted Jan 12, 2008 at 10:10 AM | Permalink

    To solve the mystery of “The Missing Typical Tropical Tropopause” we may need to call on “Captain Vorticity and his girlfriend “Divergence!”

    Sorry…couldn’t help myself, been waiting years for someone to start talking tropopause.

    Divergence shrugged, loosening her brass bra. “Talk tropooause to me, Big Boy,” she murmured.

    [fade to black]

  34. Evan Jones
    Posted Jan 12, 2008 at 10:17 AM | Permalink

    “How do they define the tropopause? ”

    Oh, the usual. (Temperature variations. Mood swings.)

  35. Posted Jan 12, 2008 at 3:53 PM | Permalink

    The question of NCEP reanalysis data accuracy is a side street: no hypothesis or argument here turns one way or the other on its accuracy. In the instance above (tropical tropopause temperature change in the late 70s), I don’t know if the NCEP reanalysis data, if accurate, would hurt, help or even affect an AGW position.

    But, for me, another short stroll down that street is warranted. Reanalysis data has the big advantage of convenience – in 30 seconds one can get reanalysis data for many parameters and atmospheric levels for any region on the planet. It’s a quick-and-dirty look. If its quality is so poor that it misses even gross trends then it has no value even as a quick-look and I then need to chunk it completely in the dumper.

    As Ryan has noted and referenced above, reanalysis data has no place in analyzing small-magnitude trends like decadal changes in temperature, and, as noted before, things like upper-atmospheric humidity are of dubious quality at best. In the instance above, the question is of the large tropical tropopause (which I define here as the 100mb level in the tropics) temperature increase reported by the reanalysis data and whether similar large swings are present in adjacent reqions of the atmosphere.

    How did the vertically-adjacent tropical troposphere behave? Here is a bar chart of the temperature change (1965-74 versus 1980-89) of the 20N-20S tropics, as reported by NCEP reanalysis. The lower levels (surface-250mb)appear to be in line, more or less, with the expected temperature change while the high troposphere and tropopause (200mb to 100mb) show the very large warming. I think the lower-stratosphere (50mb and 70mb) are consistent with other data.

    Another look is horizontally, at the 100mb levels of the mid-latitudes, which is here . The well-sampled NH shows about a 0.5C change while the poorly-sampled SH shows maybe a 0.35C decline. The tropical region shows the strong change, far greater than any change in the adjacent mid-latitudes. The tropical region, while historically poorly-sampled, is likely better-sampled than the two SH zones. It’s hard to see how incorporation of satellite data strongly affected the 20N-20S values while having a much-smaller impact on the SH values.

    What does all this mean? Well, while the NCEP reanalysis data should be avoided for small trends and used with great caution for anything else I still wonder if, in this case, it is credible in direction and magnitude.

    End of stroll 🙂

  36. Posted Jan 12, 2008 at 4:12 PM | Permalink

    Another look is horizontally, at the 100mb levels of the mid-latitudes, which is here . The well-sampled NH shows about a 0.5C change while the poorly-sampled SH shows maybe a 0.35C decline. The tropical region shows the strong change, far greater than any change in the adjacent mid-latitudes. The tropical region, while historically poorly-sampled, is likely better-sampled than the two SH zones. It’s hard to see how incorporation of satellite data strongly affected the 20N-20S values while having a much-smaller impact on the SH values.

    stratospheric temperature is dominated by plinian volcanic eruptions (Pinatubo and Chichon), simple trends don’t give honour to these huge anomalies, when endpoint bias is a likely spoiler. Better look at complete radiosonde data.

  37. John S
    Posted Jan 12, 2008 at 5:14 PM | Permalink

    This reminded me of an interesting discussion that I recently read by Kristen Byrnes on ENSO and solar. Did anyone notice that the peaks in the NCEP reanalysis match the peaks in solar cycles 21 and 22?

    By the way, Happy Birthday Kristen!

  38. Murray Duffin
    Posted Jan 12, 2008 at 5:14 PM | Permalink

    The reanalysis Tropical Tropopause Temperature Shift starting about 1977, reminds me of the surface instrument temperature jump from ca 1992 to 1998, and 1982 to 1990 on the TTTS is reminiscent of 1998 to 2006 at the surface. Hmmm. The rising temp period from ca 1976 to 1992 for the surface record doesn’t appear in the TTTS, but if we assume McKittrick is right in his belief of contamination of the surface record in both magnitude and timing, and adjust 1992 down by about 0.3 degrees C that problem goes away. Then looking at the HADCRUG Mean Temperature Anomalies from 1870 to 2004, with the “McKittrick Correction”, compared to the reanalysis TTTS curve we find 1948 corresponding with 1964,1953 with 1968, 1977 with 1992, 1982 with 1998 and 1990 with 2006. Why there should be a 15 to 16 year lag from tropopause to surface I can’t imagine. Probably this strange correspondance is just my imagination. It is rather interesting though. Since SS cycles 24 and 25 are believed by some to herald cooling for several years starting now, we might find 2007 on the TTTS curve heralding 2023. Murray

  39. Murray Duffin
    Posted Jan 12, 2008 at 5:35 PM | Permalink

    Stretching # 38 a little more, one can see suggestions of an approx 60 year cycle roughly in phase with an approx. 180 year cycle, with both near peak in the 1998-2006 period, and the 60 year cycle bottoming again about 2025, while the 180 year cycle is still going down.

  40. Cliff Huston
    Posted Jan 12, 2008 at 5:36 PM | Permalink

    So far Willis’ model makes sense to me. As a check, I decided to take a closer look at Willis’ outer shell. As shown below, it is pretty clear to me that the outer shell is mostly ozone in the stratosphere. Given that the stratospheric ozone is heated by UV from the sun, it seems that the temperature of the outer shell is going to vary depending on the ozone concentration. More ozone – higher temperature, less ozone – lower temperature. Maybe another way to look at it is more ozone means a smaller radiation window in stratosphere (and more back radiation?), less ozone means a lager window (and less back radiation?) – don’t know, I’m out of my depth here. Either way, it seems to me that ozone concentration plays a significant part in the energy budget.
    (Arrows show Brewer-Dobson circulation)
    The above from:

    Looking at stratospheric ozone changes over time is even more interesting. Seeing those changing ozone clumps over high latitude oceans, makes me wonder if ozone is a major energy source for ocean currents – but as I said, I’m way out of my depth here, just curious. The monthly ozone maps are from this NASA site: For a closer look at the above graphic, a pdf version is available here:


  41. Basil Copeland
    Posted Jan 12, 2008 at 6:05 PM | Permalink

    #16, #26

    I used the MSU data (as specifically noted in my post). I realize that the RSS data shows even more pronounced recent cooling. But I chose to use MSU because of the claim in this post at suggesting that the MSU data is more accurate.

  42. Posted Jan 12, 2008 at 10:42 PM | Permalink

    This chart ( source ) and the behavior it shows for near-tropopause air are interesting. If I’m interpreting it correctly, clear-air near the tropopause (100mb to 200mb) cools noticeably slower than does clear-air at lower levels. This is due to properties of water vapor at the very low temperatures experienced above 200mb, as I understand the article.

    One implication of this would seem to be that the upper tropical troposphere lapse rate may be lower than at lower altitudes as “warm” air delivered to 200mb by thunderstorms sort of accumulates, whereas at lower altitudes the air radiationally cools faster and sinks.

    Another might be that, as the tropical upper troposphere warms in the future due to AGW, the inhibited 100mb to 200mb layer would also warm, which would reduce the inhibition of clear-air radiative cooling in that layer. It’s as if nature puts into use this “reserve” portion of the tropical upper atmosphere for cooling purposes. Conceivably this could aid the Hadley-Walker circulation, which would aid removal of heat from lower levels.

    I tried to visualize this in cartoon 1 and cartoon 2 , though these illustrations may communicate poorly. The red dots represent the region affected by the 100mb to 200mb inhibited cooling and the density of the dots represents the extent of inhibition (more dots = more inhibition). Cartoon 1 represents things today while cartoon 2 represents the future where the upper tropical troposphere has warmed greatly. Cartoon 2 shows that the 100mb to 200mb is “put to work” cooling clear-air.

    Now at this point I’m simply trying to grasp the features of the tropical near-tropopause and how they might work. My notions may be wrong and even if they’re correct the magnitudes may be inconsequential. There’s a lot to read and learn.

    BTW, three useful references are this , this and this .

  43. Timo Hämeranta
    Posted Jan 13, 2008 at 3:36 AM | Permalink

    All, about tropopause and other atmos. layers please see:

    Lovejoy, S., A. F. Tuck, S. J. Hovde, and D. Schertzer, 2008. Do stable atmospheric layers exist? Geophys. Res. Lett., 35, L01802, doi:10.1029/2007GL032122, January 3, 2008


    “The notion of stable atmospheric layers is a classical idealization used for understanding atmospheric dynamics and thermodynamics. Using state of the art drop sonde data and using conditional, dynamical and convective stability criteria we show that apparently stable layers are typically composed of a hierarchy of unstable layers themselves with embedded stable sublayers, and unstable sub-sub layers etc. i.e. in a Russian Matryoshka doll-like fractal hierarchy. We therefore argue that the notion of stable atmospheric layers is untenable and must be replaced by modern scaling notions.”

    Well, so far, Climatology is filled with untenable idealizations….

  44. Posted Jan 13, 2008 at 4:32 AM | Permalink

    Re # 32 Pat Keating

    Evan Jones # 34 is closer than he thinks with his clever wordsmith example.

    In the slide show I referenced, there is discussion of the definition of ‘tropopause’. No single preference emerges. The WMO official definition has room for a lower and higher tropopause together, while the slide show gives profiles showing vertical gradients of a couple of Km height in the vicinity of the lower tropopause. They note definitions based on ozone concentration, slowing of lapse rate, reversal of lapse rate, pressure, multiple tropopauses at other temperature inversions up higher and comparative quiescence (less turbulence) at least. In short, one man’s tropopause is cause for other men2pause.

    Pat, why not read the reference? It has a rather lot more than I have touched on and I found it most helpful. Especially with # 43 Timo reference now just appearing.

  45. Pat Keating
    Posted Jan 13, 2008 at 8:05 AM | Permalink

    44 Geoff

    What I was getting at: they draw two narrow white lines on the chart to denote the tropopause — what parameter, and what value, is used to determine where the lines are drawn?

    I’ll be happy to read the paper. Can you provide the link?

  46. Cliff Huston
    Posted Jan 13, 2008 at 8:28 AM | Permalink

    #45 Pat,

    The link to Geoff’s slide show can be found in this post:
    Sorry about the parial link, for some reason I can’t post URLs without being eaten by Span Karma.


  47. Posted Jan 13, 2008 at 8:44 AM | Permalink

    Re #43 Understanding the detailed behavior of the tropical upper-troposphere and tropopause could make all the difference in the world in understanding global climate sensitivity to 2X CO2. It affects cloud, tropospheric water vapor, stratospheric water vapor, Hadley-Walker circulation and so forth.

    I wonder how the GCMs handle it.

  48. Tim Ball
    Posted Jan 13, 2008 at 10:51 AM | Permalink

    Making up what?

    The diagram Hans introduces has been in the literature for many years. It is presented here as a revelation. It has been a small part of the debate of climate and climate change because of the narrow and basic level of understanding of climate science or those who purport to be climatologists. The debate about two (Polar and Hadley) then three (Polar, Hadley and Ferrel) then two (Polar and Hadley) as Hans’ diagram shows has been part of the debate for many years, now it is introduced as something new here. This reminds me of discussing circulation of Strontium 90 through the upper atmosphere with a physicist who was receiving large research sums of money to study the impact of fallout from atmospheric nuclear explosions. Despite a few years of research he didn’t even know the tropopause was twice as high over the equator as it was at the poles.
    I appreciate what Steve M has done in identifying the poor use of statistics and statistical analysis, but it is just one small part of the problem in climate science, engendered by it being a generalist study in a world of specialization. The IPCC reports are a perfect manifestation of the problem and the computer climate models on which they are based are another.

    The problems go both ways, specialists not understanding the larger picture of weather and climate, and climate scientists not understanding the limits and methods of the data and specialist analytical techniques.

  49. Posted Jan 13, 2008 at 1:14 PM | Permalink

    I think that threads like this one are youth-like in the best sense of that phrase. This is a place to present and discuss things which are new to participants, to offer references for expert knowledge, to show amazement at the complexity of it all, to display ignorance, to be wrong, to raise a point, and ultimately to learn a few things.

    I also see threads like this as something of an experiment by Steve M, wherein he provides a venue, lets folks gather and see what, if anything,turns up. The signal-to-noise ratio may be poor but as little as one or two interesting points make it worthwhile.

    And I would not be stunned if, twenty years from now, we have learned that game-set-match of the whole AGW debate was found to have been in the workings of the tropical upper troposphere.

  50. Pat Keating
    Posted Jan 13, 2008 at 1:35 PM | Permalink

    46 Cliff

    I appreciate your help, Cliff.
    However, I was looking for a link to the paper, not the slide show.

  51. Cliff Huston
    Posted Jan 13, 2008 at 3:05 PM | Permalink

    #50 Pat,


    If Geoff is referring to a paper, I have no idea what it is. As to the definition of tropopause, here is what I’ve found.

    From the National Snow and Ice Data Center:
    Tropopause – The boundary layer between the troposphere and stratosphere , where an abrupt change in temperature lapse rate usually occurs. It is defined as the lowest level at which the lapse rate decreases to 2 °C km-1 or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 °C km-1. Occasionally, a second tropopause may be found if the lapse rate above the first tropopause exceeds 3 °C km-1.

    From Wikipedia:
    The exact definition used by the World Meteorological Organization is: the lowest level at which the lapse rate decreases to 2 °C/km or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 °C/km.

    Alternatively, a dynamic definition of the tropopause is used with potential vorticity instead of vertical temperature gradient as the defining variable. There is no universally used threshold: the most common ones are: the tropopause lies at the 2 PVU or 1.5 PVU surface. PVU stands for potential vorticity unit . This threshold will be taken as a positive or negative value (e.g. 2 and -2 PVU), giving surfaces located in the northern and southern hemisphere respectively. To define a global tropopause in this way, the two surfaces arising from the positive and negative thresholds need to be joined near the equator using another type of surface such as a constant potential temperature surface.

    It is also possible to define the tropopause in terms of chemical composition. For example, the lower stratosphere has much higher ozone concentrations than the upper troposphere, but much lower water vapor concentrations, so appropriate cutoffs can be used.


  52. Phil.
    Posted Jan 13, 2008 at 5:50 PM | Permalink

    Re #32

    Interesting figure. How do they define the tropopause? Pressure? Temperature (gradient)? Other?

    Here’s the whole presentation which probably contains what you want.

  53. Phil.
    Posted Jan 13, 2008 at 5:54 PM | Permalink

    Re #52

    Link didn’t work so I’ll try again.


  54. Pat Keating
    Posted Jan 13, 2008 at 8:49 PM | Permalink

    Thanks, Phil.

  55. Posted Jan 13, 2008 at 9:22 PM | Permalink

    Re # 53 Phil,

    Thank you. This was the same presentation from which I was taking diagrams. I used graphics to highlight the white trace of the original troposphere. I hope the authors do not find this objectionable.

    Pat, you can see that there are brief references to papers all through the slide show. I am not expert enough to know if these are appropriate for this discussion, but let’s hope some are helpful if new to you.

    I wanted to contrast the complexity of the tropopause shown in the slide show with the somewhat simpler impression that was coming through the CA discussion. To me, it is a modellers’ nightmare to the extent that it might prove intractible; and that models using it must be read with care.

    Re # 49 David Smith,

    Yes, I agree entirely. But it’s above the level of infinite monkeys with typewriters composing a work of Shakespeare. Some of us are used to looking at data and “smelling” that things might be good or bad. You might notice a large number of geologists and geochemists writing in. We are not so used to rapid-change time series, so maybe we are self-educating too much. Decay of Radon-222 half life 3.8 days was the main exposure I has to fast effects. I am most uncomfortable with the higher level ozone chemistry explanations, but am still learning what might be realistic.

  56. John Creighton
    Posted Jan 13, 2008 at 10:35 PM | Permalink

    Might the reason that the artic tropoause is lower bet that dry air cools faster?

  57. Sam Urbinto
    Posted Jan 14, 2008 at 12:18 PM | Permalink

    Based upon the definitions, I’d say the tropopause starts when the lapse rate falls below 2C/km and ends when it hits -2C/km

    Anyone have a definition that considers the ozone / water vapor ratios between troposphere and stratosphere to set where the tropopause starts and ends?

    And how about this:

    versus this:
    Global-mean monthly, annual and seasonal land-ocean temperature index, 1880-present, updated through most recent month

    Anomalies and Absolute Temperatures
    Our analysis concerns only temperature anomalies, not absolute temperature. Temperature anomalies are computed relative to the base period 1951-1980. The reason to work with anomalies, rather than absolute temperature is that absolute temperature varies markedly in short distances, while monthly or annual temperature anomalies are representative of a much larger region. Indeed, we have shown (Hansen and Lebedeff, 1987) that temperature anomalies are strongly correlated out to distances of the order of 1000 km. For a more detailed discussion, see The Elusive Absolute Surface Air Temperature.

  58. jae
    Posted Jan 14, 2008 at 1:20 PM | Permalink

    It appears to me that the height of the tropopause is dictated by convective forces, which are, in turn, dictated by the temperature gradient. These forces also push the ozone layer higher. ??

    Steve: jae, if you have any documentation for this, please include this with your post. Otherwise please put this in BB.

    • AK
      Posted Jan 14, 2008 at 8:21 PM | Permalink

      Re: #58

      I doubt this proves the point but it’s relevant:

      The TTL [Tropical transition layer] is a region of transition between tropospheric stability dominated by deep convection, and stratospheric stability caused by ozone heating. Convenient boundaries for this layer are the lapse rate minimum (LRM) at 10–12 km (340–350 K in isentropic coordinates), and the cold point tropopause (CPT) at 16–17 km (380–390 K). Both of these values are readily calculated from temperature soundings. The location of these levels is indicated schematically in Fig. 11. Important zonal variations in the depth of the TTL are also present, and these are noted schematically in Fig. 11.

      The TTL thus defined is related to ozone and convection in the region. The altitude of the lapse rate minimum at 10–12 km corresponds to a level generally just below the minimum in ozone in the upper troposphere. The mean position of the LRM also corresponds to the main influence of convection in the upper troposphere as observed from satellite cloud observations and divergence of the wind field. The variations of the LRM level are also significantly correlated with convective activity.

      In contrast, we find that convective activity is not strongly correlated with the cold point, the altitude of which varies coherently with the annual cycle of the stratospheric wave driven circulation (Yulaeva et al. 1994). The cold point is actually lower over some convective regions (Seidel et al. 2001), as illustrated in Fig. 11. The spatial distribution of cold point temperatures is likely a combination of several factors related to convection, including a direct cooling effect from mixing low-y air from deep convection, an indirect dynamic response to the release of latent heat in convection at lower levels (Highwood and Hoskins 1998), and the radiative cooling associated with the presence of a thick cloud deck below the cold point (Gage et al. 1991; Norton 2001). The TTL has a lower boundary dominated by tropospheric processes (convection) and an upper boundary dominated by stratospheric radiative heating and a remote response to convection.

      This analysis does not imply that convection is not important above the level of the LRM. As shown by Sherwood and Dessler (2001), even a small fraction of convection can have a significant effect on water vapor and ozone in the tropopause region. A small fraction of the time (less than 0.5%), convection does penetrate through the tropopause layer (Gettelman et al. 2002), as indicated in Fig. 11. In addition, we do not consider here the effect of horizontal (quasi-isentropic) motions within the TTL or between the TTL and the extratropical lower stratosphere. These motions, which have a preferential locations in space and time (Waugh and Polvani 2000), are likely to be important for determining the distribution of trace species in the TTL.

      The LRM at 10–12 km (350 K) is well below the level at which the clear sky radiative heating changes from negative to positive (16 km or 370 K). This implies that the main convective detrainment does not reach a level from which it can rise into the stratosphere. Deeper convection, which reaches within 1 km of the CPT or higher, is necessary to loft air to altitudes where it can reach the stratosphere.


      Variations of the tropopause layer on interannual time scales have also been diagnosed. There is a strong signal of the El-Nino Southern Oscillation, which has a strong affect on the organization of convection and on the height of the LRM, particularly in the Pacific. Over the last 40 years, the cold point tropopause has risen 200–400 m, consistent with previous work (Seidel et al. 2001). The altitude of the LRM is also rising at a similar rate, though the variability is higher at this level, so trends are not as significant. These trends appear consistent with increasing surface temperatures over the last 40 years, assuming that tropospheric lapse rates have remained fixed. We may hypothesize that the TTL may continue to rise if the warming expected from increased greenhouse gases is realized. Such a change is consistent with the sensitivity experiments of Thuburn and Craig (2002) which showed little sensitivity in a radiative-convective model to expected anthropogenic changes in carbon dioxide, because their surface temperatures remained fixed.


      The TTL can be defined as the region between the lapse rate minimum and the cold point. It has a varying thickness changing with convective activity, and is narrower with a higher base near active convective regions. The level of zero clear sky radiative heating is quite close to the tropopause.

      Gettelman, A. and P. M. de Forster, Definition and climatology of the tropical tropopause layer. Journal of the Meteorological Society of Japan, 80:4B, 911-924, 2002 PDF

  59. jae
    Posted Jan 14, 2008 at 2:36 PM | Permalink

    Steve: I don’t understand how the BB system works. Is there a guide somewhere on how to access it?

  60. jae
    Posted Jan 14, 2008 at 3:39 PM | Permalink

    Anyway, here’s one reference to what I’m trying to say:

    The uneven heating of the Earth causes the tropopause to be lower at high latitudes than
    lower ones.

  61. SteveSadlov
    Posted Jan 14, 2008 at 4:12 PM | Permalink

    jae – A few minutes ago I bumped up the BB thread. In it, is a link to the BB. Pleas go there and register – join the growing forum! (FYI – I just started a thread for OT and so called “pet theory” discussions related to energy fluxes / balance. )

  62. Posted Jan 14, 2008 at 7:07 PM | Permalink

    Here’s a temperature plot of the tropopause and surface, by latitude. I also included the 500mb level, at which half the atmosphere lies above and half below.

  63. AK
    Posted Jan 14, 2008 at 9:24 PM | Permalink


    My insert into the quote above “[Tropical Transition Layer]” should read “[Tropical Tropopause Layer]”.

    Time to stop posting and sign off.

  64. SteveSadlov
    Posted Jan 15, 2008 at 10:39 AM | Permalink

    A side not regarding today’s Theta chart (above). Look at the “Siberian dagger” pointed at the SW USA. Will it be a repeat of last year’s disasterous late Jan – early Feb freeze?

  65. jae
    Posted Jan 15, 2008 at 10:54 AM | Permalink

    63, AK, here’s another similar paper by the same authors. These papers provide a great explaination on what’s going on at the tropopause, although oddly they don’t use that word, instead preferring to refer to the zone of no heating or the cold point.

  66. AK
    Posted Jan 15, 2008 at 12:04 PM | Permalink

    Re: #66

    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.

  67. Sam Urbinto
    Posted Jan 15, 2008 at 6:13 PM | Permalink

    It’s easy to just define it as “almost no lapse rate” and arbitrarily choose a set of numbers (regardless if that’s +/-5 or +/-2 or +/-.5

    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.

  68. DeWitt Payne
    Posted Jan 15, 2008 at 6:28 PM | Permalink

    Re: #41


    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.

  69. Posted Jan 15, 2008 at 9:07 PM | Permalink

    Re #66 jae thanks for the link to the paper. Interesting stuff. Here are some odds and ends:

    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).

  70. Posted Jan 15, 2008 at 9:36 PM | Permalink

    Re #67 One thing (among many) that I can’t get settled in my mind is how the distance between Qclr and the tropopause affects the lapse rate in that layer. The temperature chart indicates that lapse rate remains rather constant until the tropopause is reached but it seems to me that the lack of strong cooling near Qclr would mess that up. That 14 to 17km layer could be a confusing one for an air parcel.

    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.

    • AK
      Posted Jan 15, 2008 at 11:03 PM | Permalink

      Re: #71
      AFAIK above the zero point the air is actually rising. Remember this is deep in the tropics, so it’s probably more like the corner between the rising leg and the horizontal poleward leg than the descending leg. One observation (I don’t remember which paper but it was one of his) is that the high cold pool extends well across the equator during all seasons, while the convective activity a little lower tends to be limited to the summer hemisphere.

      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.

  71. AK
    Posted Jan 17, 2008 at 9:52 PM | Permalink

    Re: #72, I found some research on this subject:

    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 monsoonTP 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.

  72. Posted Jan 26, 2008 at 10:49 PM | Permalink

    Figure 3 of this paper remains very interesting to me. As I read it, the upper 3km or so of the tropical troposphere (which accounts for about 20% of the free troposphere in the clear-air radiating regions of the eastern Pacific) does little or no radiative cooling, apparently due to some property of water vapor molecules at very low temperatures. I call this 3km a “dead zone”, cooling-wise.

    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.

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