Talk:Atmospheric circulation
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(William M. Connolley 20:54, 2004 Mar 10 (UTC)) I want to make some major-ish changes to this page and a set of linked atmos pages. Just for a novelty, I thought I'd discuss them first...
There are several pages (this one; Hadley cell, wind, perhaps others) all of which have partial descriptions of the atmospheric circulation on them. I think that they should be unified, probably here, and some text stripped from those pages (not all, of course).
- I would prefer not to see these pages blended. The problem is not that there is anything intrinsically wrong with this, but rather that as it stands, Wikipedia will not do a partial title search and has no effective index. Until those issues are resolved, I believe individual topics should stand as such. Moreover, topics such as 'Wind' are only peripherally related to 'Atmospheric circulation', and in the same way that I would find separate articles for 'hydrological cycle' and 'rain', so too ought 'wind' exist so as to discuss the finer points of advection.
- (William M. Connolley 19:27, 2004 Mar 12 (UTC)) I've had a bit of a rethink on this. What I shall (probably) do now is to write my own page with what I want on it and see where that fits.
But also: I think there are several problems with the existing text, which needs mods: in particular:
- The ocean transports heat too
- Indeed. And I agree mention ought be made of that. However, I have very little knowledge of the exact nature of the ocean/atmosphere interaction except for a few special cases such as Walker circulation/ENSO/etc which have captured my imagination, and rather than just add a sentence which says "And oh, by the way, the ocean is involved too" without explaining further, I felt more comfortable in saying nothing at all.
- OK, I shall do something then.
- Indeed. And I agree mention ought be made of that. However, I have very little knowledge of the exact nature of the ocean/atmosphere interaction except for a few special cases such as Walker circulation/ENSO/etc which have captured my imagination, and rather than just add a sentence which says "And oh, by the way, the ocean is involved too" without explaining further, I felt more comfortable in saying nothing at all.
- There is a load of fractal stuff in the intro to atmos circ. Firstly, this stuff is of marginal relevance: on the large aggregated scale the atmos cicr *isn't* fractal. Secondly, it isn't even true on the micro/mesoscale. The exact location of an individual cloud is *random* but on the large scale the convection is organised into patterns - not random at all. See various satellite piccies (err, I'll find one if you doubt this). And soup is the same: you tend to get a pattern of hexagonal cells. *But* this is second-order stuff: not the large scale.
- Agreed, and no reluctance to accept changes. The main point here was that even short-term meteorological change is not predictable, and it is within chaos theory that we find the reason why.
- OK, I'll "refactor" (Ed Poors phrase) that bit a bit then.
- Agreed, and no reluctance to accept changes. The main point here was that even short-term meteorological change is not predictable, and it is within chaos theory that we find the reason why.
- "It is a closed circulation loop, which begins at the equator with warm, moist air lifted aloft as an equatorial low pressure areas" needs rephrasing: the ascent *causes* the low pressure.
- Again, I agree. Ascent --> low is a fundamental assumption, and I guess the wording there needs to be looked at.
- "Some of the descending air travels equatorially" is inconsistent with the description of it as a closed cell - it needs to be all, or its not closed...
- I'm inclined to disagree here, in the sense that I don't agree that the Hadley cell is truly closed. First, there is mixing in the subsidence zones, and while I've not seen hard data to indicate the extent, I would assume it to be measurable. (I would also note that the Nuclear Winter models of several years back show ready hemispheric mixing, with the primary mixing barrier being the ITCZ. Moreover, I found a curious lack of consensus in which way upper airflow at the Rossby/Ferrel cells travelled. I must have looked at a dozen diagrams and summaries; there was an even split between those sources which showed the upper Ferrel flow as poleward (ie, the Hadley cell contributing), and those which showed the flow moving toward the equator. Since all sources are in agreement that the Ferrel cell is a secondary circulation feature, I prefer the more conservative perspective that airflow in this region is consistent with standard models, which would have air descending at the Horse Latitudes and ascending at the Polar front.
- I think the Ferrel cell is actually quite hard to understand. I'm planning to research this a bit before writing about it :-)
- I'm inclined to disagree here, in the sense that I don't agree that the Hadley cell is truly closed. First, there is mixing in the subsidence zones, and while I've not seen hard data to indicate the extent, I would assume it to be measurable. (I would also note that the Nuclear Winter models of several years back show ready hemispheric mixing, with the primary mixing barrier being the ITCZ. Moreover, I found a curious lack of consensus in which way upper airflow at the Rossby/Ferrel cells travelled. I must have looked at a dozen diagrams and summaries; there was an even split between those sources which showed the upper Ferrel flow as poleward (ie, the Hadley cell contributing), and those which showed the flow moving toward the equator. Since all sources are in agreement that the Ferrel cell is a secondary circulation feature, I prefer the more conservative perspective that airflow in this region is consistent with standard models, which would have air descending at the Horse Latitudes and ascending at the Polar front.
- Phrases such as "the rising air masses contact the tropopause at about 8 km and move along its underside toward the poles" are too simplistic: this implies air moving at the tropopause and along the surface but not in the mid-atmosphere, which is wrong.
- I agree that the wording can lead to that conclusion. I encourage you to modify it to eliminate the sense of an inert mid-atmosphere.
- OK
- I agree that the wording can lead to that conclusion. I encourage you to modify it to eliminate the sense of an inert mid-atmosphere.
- "It can be argued that the Polar cell is the primary weathermaker for regions above the middle northern latitudes" - hmm, sounds wrong. Not for midlatitudes, surely?
- Surely! At least in North America. Considering 45°N as the center of the mid-latitude zone, we see that it takes in the northern tier, but no more, of the American states, and contains all of Canada. In summer, this zone's weather is almost entirely the result of activity along the polar front, and in winter, that zone drops even further south. There are times during our winter when the entire nation is north of the polar front, yet at roughly the same latitude as Glasgow, I hardly consider my town northerly.
- Oh great, I missed "above" in the text I quoted. So you're right.
- Surely! At least in North America. Considering 45°N as the center of the mid-latitude zone, we see that it takes in the northern tier, but no more, of the American states, and contains all of Canada. In summer, this zone's weather is almost entirely the result of activity along the polar front, and in winter, that zone drops even further south. There are times during our winter when the entire nation is north of the polar front, yet at roughly the same latitude as Glasgow, I hardly consider my town northerly.
Thats enough nitpicking to be going on with...
- I'm always willing to pick a nit or two.Denni
Took a look at the changes - the article continues to look good. I remember why I included the fractal stuff. I'm sure you appreciate that fractal ≠ random. Quite the opposite, AAMOF. The point here was to help readers understand the large atmospheric movements by relating them to something human-sized. And, in fact, exactly the same rules of physics apply at the mesoscale as at the microscale. Denni 23:41, 2004 Mar 14 (UTC)
William, you might want to have a go at Air mass - now there's a sad little page that really needs a hand. I'll watch it for a while; if you decide not to tackle it, I'll give it a little help. Denni 05:11, 2004 Mar 15 (UTC)
- (William M. Connolley 23:03, 2004 Mar 15 (UTC)) Tonight I seem to be busy uploading pics of Stephenson's rocket I took last weekend... so the science will have to wait a day or two.
[edit] Does the Ferrel cell exist?
A new page, Ferrel cell is currently up on VfD. It is by an anon who says Ferrel cells do not exist. I am copying the current contents of this page to Talk:Atmospheric circulation/Ferrel cell critique to preserve it for discussion here. [[User:Dpbsmith|Dpbsmith (talk)]] 15:58, 16 Sep 2004 (UTC)
Oh, and please, by all means, anyone knowledgeable in this area please join the VfD discussion at Wikipedia:Votes_for_deletion/Ferrel_cell. [[User:Dpbsmith|Dpbsmith (talk)]] 16:01, 16 Sep 2004 (UTC)
- I am the author of the original article on atmospheric circulation, and did considerable research in preparing this article. Either the vast majority of climatologists is wrong, or the Ferrel cell exists. It is not clearly defined, since it is a secondary circulation feature, but it unambiguously occupies the space between the Hadley cell and the Polar cell, both of which have clearly defined boundaries. The Ferrel cell acts as kind of an "idle gear" between them, and, given that the Earth's circulation pattern is a closed system, is required to exist to balance the forces at work. Denni☯ 00:51, 2004 Sep 17 (UTC)
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- Added some text on Ferrel cell, agree that it's a secondary feature, which at many times is cut by Siberian or North American Highs.
[edit] Polar cell?
I find myself dubious about the contents of the polar cell bit. Over Antarctica, at least, I think that the bulk of the circulation in this cell is katabatic driven... I might even find a pic to prove this. Not sure about the north William M. Connolley 20:45, 25 June 2006 (UTC)
