Talk:Hadley cell

Dwindrim image

Dwindrim: The "number objects" you hav eused in your image are too small to read. Could you please make them bigger or perhaps upload a bigger version of the whole picture?

I also would very much appreciate it, if for no other reason than that I think the whole Wikipedia including images should be licensed under GFDL, to replace your copyright notice with the one under (from Wikipedia:Image description page).

Copyright Dwindrim. Permission is granted to copy, distribute and/or modify under the GFDL, version 1.2 any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.

---Dittaeva 11:03, 9 Feb 2004 (UTC)

Singular or plural?

Is it correct to tlk about Hadley Cells? Rich Farmbrough. 13:06, 30 December 2005 (UTC)

• Yes. Denni ☯ 19:23, 30 December 2005 (UTC)

Other way around?

The article reads: "It is at this point the Coriolis force evidences itself, leading to a clockwise rotation in the northern hemisphere and a counterclockwise rotation on the southern hemisphere".

The other way around, perhaps?

Why? I always make sign errors, but... we have mid-lat westerlies, and tropical easterlies, which implies a clockwise circ for air moving from mid-lat to trop. And the same, aloft. William M. Connolley 11:31, 26 February 2006 (UTC)

Incidentally... if this is confusing because lows in the NH spin counter-clockwise... see http://en.wikipedia.org/wiki/Coriolis_effect#Flow_around_a_low-pressure_area - the crucial point being that CF is *outwards* balanced by PGF inwards. I hope. William M. Connolley 11:38, 26 February 2006 (UTC)

Extraneous Material

The article reads: "As with any idealized system, it is important to realize that it is precisely that. A Hadley cell is bound as much by the laws of chaos as by the laws of thermodynamics, and what is here today may be there, or somewhere else, tomorrow."

If no one objects, I'm going to trim this heavily -- it's not specific to the topic.

kraemer 21:22, 4 July 2006 (UTC)

Poorly written

This article is very poorly written, and not being an expert in this field, I wouldn't even know how to fix all of it. Let's look at the first paragraph, as an example:

The major driving force of atmospheric circulation is solar heating, which on average is largest near the equator and decreases as one moves polewards. The atmospheric circulation tries to eliminate this gradient by transporting energy polewards from the tropics to higher latitudes. The mechanisms by which the atmosphere decides to accomplish this task are very different in tropical latitudes than in the rest of the atmosphere.

The major driving force of atmospheric circulation is solar heating: This is an awful first sentence, for a number of reasons. First, there is no indication as to what all this has to do with a Hadley cell until the end of the 2nd paragraph. Moreover, the wording is poor. Using the phrase "Major driving force...is solar heating" involves using the literary device of personification, which probably shouldn't be used in a formal text like this. polewards: I can guess what this means, but it is a technical term that probably shouldn't be used the very first time the concept "towards the Earth's poles" is mentioned. Perhaps write out "towards the Earth's poles" for the first mention, then use "polewards" for later mentions. The atmospheric circulation: does this really need the article "the"? this gradient: What gradient? The difference in solar heating? NB: this isn't a problem with English per se (in case a non-native speaker wrote the article), but a more general problem of having an ambiguous discourse referrant. At any rate, even if this does refer to the difference in solar heating, it still doesn't make any sense: atmospheric circulation can elimate differences in heat (noun), but not differences in heating (verb). polewards from the tropics to higher latitudes: sloppy, is there anything else polewards could mean? You need to put "i.e." or "in other words," here. the atmosphere decides...: the atmosphere cannot decide anything, it is inanimate. —Preceding unsigned comment added by 129.215.218.236 (talk) 15:47, 27 September 2006

(Actually, this is not true . It makes no sense to talk about reducing the gradient in "heat" -- this terminology went out of style in the 19th century with the caloric theory of heat -- thermodynamics teaches us to talk about heating rates, not heat. And the energy transport by the atmospehre does reduce the gradient in net heating rates, by changing the infrared cooling that is a function of temperature -- climateguru).

Thanks, I don't think the writing is THAT bad. --Steve (talk) 04:14, 30 March 2009 (UTC)

Yes, "this gradient" is the gradient in solar heating William M. Connolley (talk) 23:18, 5 August 2010 (UTC)

Hadley Cell Units?

Usually appears that the range is about +/- 5 cm/sec. What are these units? About +/- 0.2 what? the closest guess would be feet per minute. Would like something better than my guess. --Steve (talk) 04:12, 30 March 2009 (UTC)

References

NASA's Picture of the Hadley Cell

This picture shows the ITCZ at aproximatly 5 degrees north. This would only be the case during June as the ITCZ migrates as the suns position over the equator changes. This is not mentioned which gives the false impression that the ICTZ is perminantly at 5 degrees north. Jonathan

Angular momentum conservation mechanism

According to the only reference in this article, Anders Persson, Hadley's Principle: Understanding and Misunderstanding the Trade Winds, History of Meteorology 3 (2006), the mechanism described in this article is the erroneous and discredited Hadley explanation. To quote from this reference: 'According to Brunt, “In practice the motion of a mass of air through a large range of latitude, while retaining its original angular momentum about the axis of the earth, can never arise.” The angular momentum conserving model is therefore out of place for the atmosphere.'

In short, the Mechanism section of this article is contradicted by its only reference and thus needs to be revised to reflect the correct physics.

Drphysics (talk) 19:00, 6 September 2009 (UTC)

The Hadley circulation is the bit of the atmosphere (at least the upper branch) where conservation of ang mom does apply. I think. Held, etc. William M. Connolley (talk) 23:19, 5 August 2010 (UTC)

Hadley cell expansion

Needs some more work William M. Connolley (talk) 23:18, 5 August 2010 (UTC)

Merge with convection cell?

This article appears to exist primarily to mop up detail from atmospheric convection, and shares much of its information with convection cell. Should it be changed to focus on the specifics of Hadley cells, with plenty of links to the information contained in atmospheric Convection cells, Rayleigh-Bénard convection, etc? —Preceding unsigned comment added by 213.81.83.42 (talk) 06:43, 29 October 2010 (UTC)

Strange units in diagram description.

The map/diagram talks of velocity and lists the units as Pa/S. A velocity should have units of m/s (note also that the SI unit of time is a lower case s - as far as I remember). A pascal (Pa) has units of N/m², giving Pa/s => kg/m.s³. In any case, this is not what is normally called velocity, or is this some kind of meteorology convention? 1812ahill (talk) 00:01, 26 October 2011 (UTC)

This is in fact a measure of vertical velocity when you are using pressure as a vertical coordinate, which is extremely common in atmospheric science. A very crude way to switch between pressure velocity and conventional vertical velocity is through a manipulation of the hydrostatic equation: omega ~ gravity*density*w, where omega is the vertical pressure velocity and w is the vertical velocity in m/s. Nadavis 15 Nov 2011 (UTC)

External links modified

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Subtropical deserts

Re “Many of the world's deserts are located in these subtropical latitudes. However the deserts do not extend to the eastern side of the various continents because of ocean currents caused by the Trade Winds.“

     Interesting paragraph — but shouldn’t this refer to the moisture (rather than “ocean currents“) carried by the tradewinds? 47.188.133.212 (talk) 22:16, 21 June 2022 (UTC)

Recent expansion and additional work

I recently rewrote and expanded the article, since it is an important component of the global atmospheric circulation and was lackign in detail. The hope is that this vital article can be brought to at least Good article status. The Hadley cell is a far-reaching topic, so I'm hoping to get more eyes on the article to help satisfy the "Broad in its coverage" criterion and cover all major aspects of the Hadley cell. The article is potentially quite far from being comprehensive, but maybe as a start we can at least get to all the major points. Below I've highlighted some key areas where I figure the article might need additional context / content / work on:

• Is the framing of the Hadley cell presented in the article as a tropical, thermally direct overturning circulation the right way to talk about the Hadley cell? Should we be more broad or more concise?
• Is a more rigorous discussion on the dynamics of the Hadley cell needed, including mathematical descriptions of energy transport / conservation and circulation dimensions or behavior?
• The role of the ocean and continents – their physical properties and their distribution – in shaping the Hadley cell
• Teleconnections (e.g. ENSO) and their affect on the Hadley circulation, and vice versa
• Regional variations of the Hadley cell, or "regional Hadley cells"
• The later history of the development of the Hadley cell, such as the development of later models like the Held–Hou model
• Further discussion the effect of climate change on the Hadley cell, both historically and in model projections
• How do human influences physically/dynamically result in Hadley cell expansion?

Additionally, more free images would be nice — perhaps someone could find/produce a useful streamfunction plot for the equinoctial and solsticial Hadley cells? — TheAustinMan^{(Talk ⬩ Edits)} 21:22, 15 February 2023 (UTC)