By Andy May
It all began eight years ago when I read and reviewed Ronan and Michael Connolly’s first three papers on their ideas about the “molar density intersection” which is located just below the tropopause. I was quite fond of Michael Connolly, who sadly and suddenly passed away in August 2025, we all miss him.
As I explain in my paper (May, 2025), the molar density atmospheric profile forms two intersecting least squares best fit lines when plotted versus air pressure as illustrated in figure 1. The Connolly’s intersection is identified with the horizontal dashed line.
The data used to make figure 1 is from 1,136 weather stations, each with multiple weather balloon radiosonde ascents per day from 1990 to 2025. This is a subset of the full 2,921 weather station IGRA2 radiosonde database. The radiosonde data used is comprised of ascents that had at least 90 pressure levels, so they define the troposphere well. This subset was reduced to bin averages vertically in 10 hPa (hectopascals are 100 Pascals, or one millibar) bins. Thus, figure 1 is the overall global average molar density intersection plot and it still shows a distinct kink and intersection at 204 hPa (~11.8 km). This change in slope is unexpected, the formula for molar density is:
In the equation “D” is the molar density in mol/m3, “P” is the pressure in Pascals, “R” is the gas constant (= 8.3145), and “T” is the temperature in Kelvin. As the equation makes clear, the slope of the molar density versus pressure plot should be a line of constant slope, if the atmospheric composition and state do not change. But as figure 1 shows a distinct change does take place, on average, at about 11.8 km. At that altitude the average molar density is 11.9 mol/m3, the average temperature is -53.8°C, and the relative humidity is 21 %. The intersection is just below the classic WMO tropopause everywhere on Earth, except at the very cold South Pole, where neither the classic WMO lapse-rate tropopause nor the intersection techniques work very well (WMO & Ashford, 1957) and (Xian & Homeyer, 2019).
The classic lapse-rate WMO tropopause doesn’t work very well in the higher latitudes in general. It frequently defines multiple tropopauses, probably because atmospheric Rossby waves cause mixing of tropospheric and stratospheric air (Xian & Homeyer, 2019). As a result of the confusion, many replacement definitions have been proposed (Connolly et al., 2024), (Reichler et al., 2003), and (Reutter & Spichtinger, 2025). These are based on relative humidity changes, ozone concentration changes, and other changes that take place in that region of the atmosphere. However, the most globally consistent measure is the molar density intersection. The only problem is we don’t really know why it occurs or why it is so consistent. But regardless of the cause, it is a good marker, and its detection can be automated. The R code to detect it is available in the supplementary materials to my paper, as well as in the paper’s Appendix (May, 2025).
Michael and Ronan did not map their weather balloon results; they always looked at the results through atmospheric profiles and never in 3D. When Michael Connolly gave a talk in Tuscon, Arizona (Connolly M. , 2025) he received an interesting question from John Clauser (Connolly M. , 2025) (see here, about 38 minutes in) about ocean gyres and the Hadley circulation. In short Dr. Clauser thinks the gyres are evidence of the Hadley circulation (Hadley, 1735) and Dr. Michael Connolly thought they are not (Connolly et al., 2021).
That conversation lit a fire under me, and I wrote some R programs to map and profile wind speed and direction. It turns out that the Hadley circulation is real and it does relate to the ocean gyres. Figure 2 diagrams the circulation.
Figure 2 (as well as figures 3, 4, and 5) show speed-weighted vector-averaged “wind arrows” where the x axis is wind speed, the y axis is air pressure, and the arrows point in the direction the wind is blowing (opposite the meteorological convention). The details of how the wind direction is computed, and the R code can be seen in the supplementary materials and in Appendix A of the paper. Figure 2 is only for the month of January and for weather stations between 10°S and the equator (slice “-10”, slices are named for their southern boundary). The wind direction changes when the wind speed slows between about 450 to 500 hPa. Above the slow down, the winds are blowing away from the equator and the Intertropical Convergence Zone (ITCZ, about 5°S in January on average) and the speed of the wind increases with altitude. Below the slow down the winds reverse and blow equatorward (northwest in this case) and speed slightly increases toward the surface.
The key problem with the molar density discussion in Connolly and Connolly (2014 and 2014a) was they did not map their results. Thus, they could not see evidence of the Hadley circulation (Hadley, 1735) and speculated that it might not exist (Connolly et al., 2021). In May 2025, I argue that it does exist, but it is a complex 3D circulation and not a simple 2D north-south circulation as it is often portrayed in the literature (Dima & Wallace, 2003) and (Cook & Webster, 2004). A similar view of a more complex 3D Hadley circulation is presented in (Karnauskas & Ummenhofer, 2014), where they also explain some of the processes involved.
High in the troposphere, the rising air in the ITCZ is diverted horizontally when it hits the highly stratified stratosphere and progresses poleward in both hemispheres. The force of the rising air in the ITCZ also pushes the tropical stratosphere higher than 14 km. It then begins a long path down to the surface as water vapor freezes out of it, which increases the air density (water vapor has a molecular weight of 18 versus 29 for dry air). When the dehydrated air reaches the surface, it warms and creates a high-pressure arid region.
The Hadley circulation is hard to detect because the area of rising humid tropical air, the center of the ITCZ, is constantly moving north and south with the sun as the seasons change. You must check the air flow at the right spot and at the right time. Fortunately, the ITCZ in January is roughly at 5°S (May, 2025) on average and in the Northern Hemisphere winter the Hadley circulation is slightly stronger than in other months (Nguyen, et al., 2013).
The other evidence for the existence of the Hadley circulation are the subtropical deserts, like the Sahara, the Australian Outback, and the Atacama Deserts, these desert regions are circled in figure 3.
The upper tropospheric wind in the desert regions is blowing in the opposite direction from the tropical winds and often with a slightly poleward vector. These deserts occur where the upper troposphere winds reverse direction and have the slowest horizontal wind speed, thus they are over high-pressure regions where the wind is falling, taking dehumidified air with them. The ocean gyres that also result from this circulation are visible in the upper troposphere, but not as clearly as they are in the lower troposphere as shown in figure 4.
Figure 4 shows how the location of the continents, combined with the lower troposphere wind direction reversal at low wind speed between 20° and 30° north/south help form the gyres. The propagation of the low wind speed wind direction reversal is illustrated in figure 5.
As figure 5 shows, the wind direction reversal starts at about 300 hPa (~9 km) at the equator in April and disappears at the surface in the 30°N to 40°N latitude slice. The surface wind direction (again a speed-weighted vector-average) is slightly poleward in the 10°N to 20°N slice but turns equatorward in the 20°N to 30°N slice. A similar pattern is also seen in the Southern Hemisphere.
Discussion
When studying a 3D problem, it is best to study it with 3D tools. Simple 2D graphs will not do the job. When the radiosonde data is mapped and profiled using speed-weighted vector-average wind arrows the Hadley circulation shows up. It isn’t seen in 2D plots of wind direction because the general wind direction in the critical latitudes is either east-west (tropics) or west-east (mid-latitudes), the critical low-speed wind direction shift is not normally seen. The low-speed wind speed change in direction in the sub-tropics is narrow and constantly moving with the seasons. This pattern can be seen in the maps in the supplementary materials where the monthly movements of the ITCZ are noted.
The entire Hadley circulation can only rarely be seen in one profile, as it is in figure 2, because it is a complex 3D wind pattern that changes continuously with time. We could call it a complex 4D wind pattern. Figure 2 is ideally located such that the ITCZ is always located in that latitude slice in that month, and it is near the equator where the rising humid air has pushed the molar density intersection very high. The ITCZ is relatively narrow, particularly the rising air column portion of it, so it is hard to locate. The region, in both hemispheres, where the cool dehydrated air falls is very large, but the meridional wind component is small.
The easiest, and most consistent, way to see the Hadley circulation is to profile the falling low-speed wind direction reversal shown in figure 5. This low-speed region reaches the surface at about 30°N/S, the latitudes of the large ocean gyres. This is also the latitude of the subtropical deserts seen in figure 3. It is the movement of the low-speed wind direction shift that best and most clearly characterizes the Hadley circulation.
This is all discussed in much more detail in my new paper, which can be downloaded here. It is in opposition to what Michael has written and believed, but I’m very sad that he passed away before I finished this work. Knowing him, he would not be upset, he would enjoy seeing the data presented this way and excited to debate the ideas with me. He was always a very data-driven guy.
Code availability
A zip file that contains the R code, additional plots mentioned in the text of the paper, along with some test data can be downloaded from (https://andymaypetrophysicist.com/wp-content/uploads/2025/11/supplementary_materials_May_2025.zip) or (May, 2025b). The zip file also contains some code documentation and the plots used to choose the ITCZ latitudes for each month.
Data availability
The data used can be downloaded from (ftp.ncei.noaa.gov/pub/data/igra) or (https://www.ncei.noaa.gov/products/weather-balloon/integrated-global-radiosonde-archive). The ftp site is far more convenient, but it requires an ftp app, like filezilla.
This paper is also available on Researchgate here.
Afterword
Some will ask why I published this paper via OSF and outside the normal peer-reviewed journal route. It is simple, I’m retired and unless I have a specific invitation for a paper, like with our AJES article, or get a publication fee waiver, it is too expensive and not worth the money. I suppose if I were younger and needed to purchase the prestige of a peer-reviewed journal, it might be worth it, but the fees are several thousand dollars and I’m not interested. The true value is in the study I did and how I wrote it up, what journal it is in is just vanity. People will read it and comment regardless of where it is published.
Works Cited
Connolly, M. (2025). 20 Million weather balloons: How this data shows that all the climate models are based on wrong assumptions. Retrieved from https://www.youtube.com/watch?v=48Hp9CqSlMQ&t=1026s
Connolly, M., Connolly, R., Soon, W., Velasco Herrera, V., Cionco, R., & Quaranta, N. (2021). Analyzing Atmospheric Circulation Patterns Using Mass Fluxes Calculated from Weather Balloon Measurements: North Atlantic Region as a Case Study. Atmosphere, 12. https://doi.org/10.3390/atmos12111439
Connolly, M., Dingley, O., Connolly, R., & Soon, W. (2024). Comparing Different Tropopause Estimates From High-Resolution Ozonesondes. Earth and Space Science, 11(5). https://doi.org/10.1029/2024EA003584
Cook, K., & Webster, P. (2004). The Elementary Hadley Circulation. In H. F. Diaz, & R. S. Bradley, The Hadley Circulation: Present, Past and Future. https://doi.org/10.1007/978-1-4020-2944-8_2
Dima, I. M., & Wallace, J. M. (2003). On the Seasonality of the Hadley Cell. Journal of the Atmospheric Sciences, 60(12), 1522 – 1527. https://doi.org/10.1175/1520-0469(2003)060<1522:OTSOTH>2.0.CO;2
Hadley, G. (1735). Concerning the cause of the general trade-winds. Phil. Trans., 29, 58-62.
Karnauskas, K., & Ummenhofer, C. (2014). On the dynamics of the Hadley circulation and subtropical drying. Climate Dynamics, 42, 2259-2269. https://doi.org/10.1007/s00382-014-2129-1
May, A. (2025). The Molar Density Tropopause Proxy and its relation to the ITCZ and Hadley Circulation. OSF. https://doi.org/10.17605/OSF.IO/KBP9S, URL: https://osf.io/eq75t
May, A. (2025b, November 28). Supplementary Materials: The Molar Density Tropopause Proxy and Its Relation to the ITCZ and Hadley Circulation. https://doi.org/10.5281/zenodo.17752293
Nguyen, H., Evans, A., Lucas, C., Smith, I., & Timbal, B. (2013). The Hadley Circulation in Reanalyses: Climatology, Variability, and Change. Journal of Climate, 26(10), 3357 – 3376. https://doi.org/10.1175/JCLI-D-12-00224.1
Reichler, T., Dameris, M., & Sausen, R. (2003). Determining the tropopause height from gridded data. Geophysical Research Letters, 30(20). https://doi.org/10.1029/2003GL018240
Reutter, P., & Spichtinger, P. (2025). The frosty frontier: redefining the mid-latitude tropopause using the relative humidity over ice. Atmos. Chem. Phys., 25, 16303–16314. https://doi.org/10.5194/acp-25-16303-2025, 2025
WMO, & Ashford, O. M. (1957, October). Meteorology – A three-dimensional science, second session of the commission for aerology. WMO Bulletin, 6(4), 134-138.
Xian, T., & Homeyer, C. R. (2019). Global tropopause altitudes in radiosondes and reanalyses. Atmospheric Chemistry and Physics, 19(8), 5661–5678. https://doi.org/10.3390/atmos12111439
Nice work. The movement of mass is the key to understand climate and identify driving mechanisms. Look at wind directions at altitude..it switches to the same direction as earth is spinning. CO2 is no climate driver.
https://reality348.wordpress.com/2016/09/27/41-wind-and-water/
Plus an overall summary.
https://reality348.wordpress.com/
Three part series worth a read.
https://open.substack.com/pub/josephfournier/p/rethinking-drought-paleoclimate-evidence?utm_source=share&utm_medium=android&r=17bedn
I mapped and profiled the movement of atmospheric mass every which way from Sunday because it seemed obvious that it was important. It was all over in the literature also, see Adam, et al. in the bibliography. But it was only part of the story, and nothing jumped out at me in that area. The R code I wrote does compute the mass flux, maybe if you download it and look at the results you will find something significant, I didn’t see it. Like I say in the post and in the paper, the most important and general indicator of the Hadley circulation that I saw was the movement of the zero-wind-speed wind direction shift.
Cheers. Reading in more depth, the trend here looks off. As you highlight later, Not linear, and likely cyclical.
Good eye. I noticed that also, but I’m not sure what to make of it other than the trends in that data look nothing like the log(CO2) trend. None of the temperature trends look anything like log(CO2), all are severely nonlinear.
More on the ITCZ discussed here.
https://open.substack.com/pub/josephfournier/p/clouds-in-motion-how-pacific-walker?utm_source=share&utm_medium=android&r=17bedn
It is a very steep trend. 0.7 C/decade. 7 C/Century.
True. We’ll see if it lasts. Also noted in the paper is that the middle troposphere has a lower gradient, and upper troposphere even lower than that, opposite of what is predicted by the climate models. Thus, there is no support for the model “hot spot,” a key feature of modeled greenhouse gas caused warming. It is missing globally and in the tropics where it should be strongest.
Water vapour (H2O) has a molecular mass of 18g per mol (2 +16), not 14!
Thanks! I fixed the typo and checked the paper; it is correct in the paper.
I was worried that even the water molecules had started taking Ozempic!
It was transmuted into N2 by that waskally CO\2! there’s nothing that CO2 can’t do.
Andy, certainly no offense intended, and hopefully none taken, but at present I see two opinions opposed to each other. Notwithstanding Feynman saying –
I can’t see any substantive physical reasons either for or against either view.
Without belabouring the point (too much), there can dangers in believing what is “well known”. For example “warm air always rises” – except when it doesn’t. “Warm air flows toward the poles” – except when it just expands and contracts in place. “Warm is less dense than cold air” – except when it isn’t. And so on.
I suppose that your view that
implies that the height of the atmosphere is greater at the Equator is due to rising air, where others might say it’s due to centrifugal force and lower overall density (compared to the poles).
One paraphrase of Newton’s First Law is “Every change in a body’s state of motion is due to impressed forces.”. Now a particle of air will stay precisely where it is in relation to the Earth’s COG, unless a force is impressed upon it. People seem to equate air and water to heat, and blithely assume that both will wander off towards colder regions elsewhere on a sphere to which they are attached by gravity.
Now a body of hot water water will transfer heat to an adjacent block of ice, but neither will be inclined to move either to or away from the position which gravity holds them in, without the “impression of a force”.
So, while your view is as valuable as an opposing view, without some further explanation of the physics underlying your view, it just just seems another example of Flynn’s Law – “For every opinion there are one or more opposing opinions, each being worth exactly what you are prepared to pay for it.” <g>
Once again, no offense intended.
In the same spirit as your non-offencenitiousness, i wish to point out that things like convection and osmosis exist, but I would not call them forces, and also, electrostatics explains a lot more about our atmosphere (and things like convection) than gravity does, and lastly I don’t think centrifuge works exactly the way you think your references understand it.
Unless this gravity of yours is not a force, but a flexible string attached to each atom, straight to the geographic centre of the planet I guess. I shall not argue.
No offense meant, of course…
Maybe a closer look at the data will show a sudden upwell where that air rises, distinct from the smooth increase one would expect from your centrifuge.
I will leave that bit of detectoring in your self-implied detail-precise hands?
Hot air doesn’t always rise. An area of increased surface temperatures may be associated with high pressure, often called a heat dome –
One reason for the atmospheric “bulging” –
The above are quick grabs from Google, and as such “may contain mistakes”.
I accept your opinions are worth as much as mine. Others might choose to seek facts rather than opinions.
Michael,
I suggest you read the paper, download the R code and check it out. Your comment is far too general and obtuse to respond to in a comment. Be a little more specific.
Within the ITCZ narrow zone, we can be absolutely certain that energy is moving away, otherwise the SST would be over 86 deg. C, and it is actually between 20 and 30 deg C. Very little heat transfer takes place via radiation, outside the lower few meters of the atmosphere, so energy is transported via mass flux via wind. The meridional mass flux is near zero in the ITCZ (see the ITCZ section of the paper) and the molar density and tropopause are pushed up between 20S and 20N (see figure 6 in the paper), thus upwelling air in the ITCZ and the surrounding region is occurring.
At the surface the tropical winds are easterly, but at some height, the speed drops to zero, and they change to westerlies, this happens all around the world. The zero wind speed wind direction reversal point starts very high (<300 hPa, >9km) at the ITCZ and drops steadily and reaches the surface at about 30 deg. N/S. As the zero wind speed wind direction reversal reaches the surface the ocean gyres and arid deserts form. In essence that is the Hadley circulation, it is not a north/south wind, it is a reversal of the surface easterlies in the tropics changing to mid-latitude surface westerlies north of ~30N.
Now that said, as documented in the paper, do you have a specific question?
Andy, I’m not asking you any questions. I’m just pointing out that your speculation doesn’t appear to be supported by the laws of physics.
You say, for example, –
Yes. All matter above absolute zero radiates IR – continuously. As Fourier pointed out (and so did Tyndall, using different words), the Earth loses all the energy it receives from the Sun to outer space. By radiation, of course.
All heat (energy that is transferred from one body to another as the result of a difference in temperature) is transferred by radiation, whether you want to believe it or not. Just saying “otherwise” is pointless. It isn’t, is it?
Unless they’re not?
As you say, you have one speculation, other authors differ. In my worthless opinion your post is wishful thinking, but others may disagree.
Michael,
You write:
“All heat (energy that is transferred from one body to another as the result of a difference in temperature) is transferred by radiation, whether you want to believe it or not. Just saying “otherwise” is pointless. It isn’t, is it?”
I do not believe that, and I can’t believe you do either. Heat is transferred from one place on Earth, for example the tropical ocean surface, to another place, for example the middle latitudes or the upper troposphere in four well-known ways. Convection, latent heat in water vapor, conduction (short distances), or radiation. Radiation is more complex since how far it goes depends upon frequency, which in turn depends upon the temperature where it is emitted, which varies all the time.
I explain this much more thoroughly here:
https://andymaypetrophysicist.com/2025/02/01/energy-and-matter/
The post is just an introduction, to understand what I wrote you will need to read the paper, the evidence is in it.
Andy, it happens to be true, but of course you don’t have to accept it.
That’s just wishful thinking, at other than a miniscule scale. The Earth revolves, and even the ocean surface heats during the day, cools during the night. The ocean depths are gently warmed from below, causing chaotic convection currents.
You probably don’t believe Fourier, or John Tyndall, either. For example, Tyndall commenting on the ancient custom of ice-making in Bengal says “The water is a powerful radiant , and sends off its heat copiously into space”. Turning liquid water into ice, by letting it radiate energy faster than it is replaced. Primitive observations put to use in different places, for millenia.
Everything radiates IR, and if this energy loss is not replaced, matter cools.
The Earth has demonstrably cooled over the past four and a half billion years, but you don’t have to accept that, either.
So to me, you appear ignorant of the reality of physical laws, and gullible enough to believe that heat on one part of the Earth magically transports itself to another place for no particular reason.
Andy, you’re dreaming. From your link –
That’s rubbish, for a start. You might have noticed that the surface cools at night. Tyndall and others explained why over a century ago.
But even if your statement was true, then “most radiation” being absorbed would do no more than slow the rate at which the surface cooled, as Tyndall also explained.
Sorry Andy, but appealing to your own authority is not persuasive, in the face of observable fact.
The Earth has cooled over the past four and a half billion years, notwithstanding GHGs, fossil fuels, or the high levels of ignorance and gullibility displayed by so-called “climate scientists”.
Accept reality. No “Greenhouse Effect”. No GHGs. Climate is the statistics of weather observations, and neither controls, nor is responsible for, anything at all (apart from the fantasies of “climate scientists”).
Hallo Andy, have to comment on this section of your article, since it gives the impression that you believe the HC is driven by the rising air in CB’s in the ITCZ. Apologies if this impression is incorrect.
The actual driver of the HC is the difference in surface temperatures between the equator and higher latitudes. The lower troposphere in the tropics is warmer and thus more expanded then at higher latitudes. This creates a pressure difference AT ALTITUDE and thus air moves from the equator towards both poles. This air accumulates in the subtropical jets due to the Coriolis effect and thus create there high pressure at the surface. The air moving away from the equator AT ALTITUDE creates low pressure at the surface. This surface pressure differential causes the trade winds.
So even without CB’s in the ITCZ we would see a HC driven by uneven solar heating of the surface.
Ben, Please define HC and CB. I’m not sure what you are asking. As for surface pressure, that is mostly controlled by TPW (total precipitable water) in the air column above the pressure point. Air movements only affect surface pressure to the extent of the specific humidity of the moving air compared to the air it replaces.
Sorry, seemed obvious.
HC = Hadley Circulation
CB = Cumulonimbus, the high rising (thunder)storms.
Surface pressure is just the weight of the entire column pressing on the surface, whatever the contents of the column.
Air at altitude moving from the equator towards the poles reduces the total weight of the column at the equator, thus creates a lower surface pressure.
The mechanism I describe is very basic, exactly the same as the sea breeze that occurs due to uneven heating of land vs sea.
Ben,
As I explain in my paper:
This poleward mass transport aloft “piles up” air at higher latitudes, raising MSLP (mean sea-level pressure) in the subtropics while the ascent depletes mass near the equator, lowering MSLP there. The compensating surface flow is then equatorward (trade winds), closing the cell.
This is sort of what you are describing, but evaporating water in the ITCZ is the driving force in this Hadley circulation and the evaporating water would not make any difference except it is hot and contains low density water vapor. The two driving forces are heat (temperature) and water vapor containing a lot of latent heat.
Basically I agree with your description, I just want to make sure that temperature and TPW are included, since they are the important factors in the Hadley cell, they provide the energy.
Great. I reacted initially since what you describe in the post is something entirely different.
The driving force of the HC is the sun, which unevenly heats the surface, causing uneven expansion of the atmosphere.
A sea breeze can develop on a perfectly cloudless day.
The HC can run equally well without CB’s developing in the ITCZ, the tradewinds blow day and night.
Where in the post does it say something different? You don’t provide a quote. The post does not discuss the sun, sea breezes, or cumulonimbus clouds. It discusses how the Hadley circulation occurs in reality and how to detect it with weather balloon data. I think you misunderstood the article and post. Not sure why you misunderstood though, which is why you should quote the confusing bit.
Same with Michael Flynn, he is also talking about stuff that has nothing to do with the post or article. Both of you should be more clear about what you are addressing.
The force of the rising air probably describes the CB’s that burst through the tropopause, but they don’t push the stratosphere higher than 14km.
These CB’s aren’t necessary for the HC.
The rising air is caused by air moving towards the poles AT ALTITUDE being replaced by air from below.
The long path down to the surface seems to point to the distance between the ITCZ and the high pressure areas, where
“the dehydrated air reaches the surface, it warms and creates a high-pressure arid region.”
Air from the ITCZ travels AT ALTITUDE towards the poles and causes the high pressure at the surface while accumulating in the subtropical jetstream. At the surface air moves out of the high pressure area and thus causes from from above to sink to replace it.
This sinking air will warm more or less according the dry adiabatic lapse rate and thus arrive at the surface already warmed.
That is what I thought. I could quibble about some of the details of your wording, but you are saying almost exactly what I write in the post and paper. And you still don’t quote anything I wrote that you disagree with.
You don’t seem to think that the stratosphere is pushed above 14 km in the tropics, but I show data in the paper that establishes that fact. It seems you do not disagree with anything I wrote.
Maybe you think individual air molecules do not make the trip? That is clearly a pointless argument and who cares? Molecules do not have names. The Hadley circulation exists and works as I described.
I have no idea what you are talking about when you write “AT ALTITUDE” in all caps. Have you tracked any individual molecules? I doubt it, that is a silly argument. As I write in the post, the zero wind speed wind direction shift does descend to the surface at about 30N/S. Whether the air molecules are the same is not important or known.
It occurred to me this morning that your comment:
Might mean that you believe the “Hadley Cell” cartoon images like attached literally. As the post and paper make clear, the radiosonde data do not support this cartoon. The tropical circulation is east to west at the surface and west to east in the upper troposphere, the switch in direction starts very high at the equator and moves to the surface around 30 deg N/S.