Is the Hadley Cell Responsible for Global Desert Patterns?

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Discussion Overview

The discussion revolves around the role of the Hadley cell in shaping global desert patterns, particularly focusing on the Sahara Desert and its counterparts in the Southern Hemisphere. Participants explore the complexities of climate formation, including geographical influences and the limitations of simplified explanations found in sources like Wikipedia.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that if the Hadley cell is responsible for the Sahara, similar desert patterns should exist symmetrically in the Southern Hemisphere.
  • Others point out that deserts like the Kalahari and Namib exist in the Southern Hemisphere, but question why these areas are not Sahara-like deserts across the entire continent.
  • It is proposed that local geography, ocean currents, and other climatic factors also significantly influence desert formation, not just the Hadley cell.
  • Some participants express concern over the oversimplification of the Hadley cell's role in sources like Wikipedia, arguing that it should acknowledge the complexity of factors involved in desert formation.
  • There is a discussion about the reliability of Wikipedia as a source, with some participants criticizing its editorial nature and lack of detailed explanations.
  • One participant mentions the historical climate of the Sahara, suggesting it was once green, indicating that desertification is a more complex process than just the influence of the Hadley cell.
  • Another point raised is the discontinuous nature of desert formations, with examples from various continents illustrating how deserts do not extend uniformly due to various climatic mechanisms.
  • Questions are posed regarding the idealized representations of the Hadley cell in diagrams and how they may not accurately reflect real-world conditions.

Areas of Agreement / Disagreement

Participants generally do not reach consensus on the extent to which the Hadley cell alone accounts for desert formation. Multiple competing views remain regarding the influences of geography, ocean currents, and historical climate changes.

Contextual Notes

Limitations include the reliance on simplified models of climate systems, the potential for misinterpretation of sources, and the complexity of interactions between various climatic factors that are not fully explored in the discussion.

  • #31
physicsponderer said:
It's not evident to me. Would you care to explain it?
Those very long contiguous streamers of cloud banks show the circular interaction of air masses on the scale of thousands of kilometres, notably between temperate and polar latitudes.
 
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  • #32
DaveC426913 said:
Those very long contiguous streamers of cloud banks show the circular interaction of air masses on the scale of thousands of kilometres, notably between temperate and polar latitudes.
Would you care to expand on that?
 
  • #33
physicsponderer said:
I had hoped for some discussion.
You got it. You used a crappy, and ill-specified source for your statement and you got a discussion of your crappy and ill-specified source. As said earlier in the thread, that's why PF insists on acceptable and well-specified sources.
 
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  • #34
phinds said:
You got it. You used a crappy, and ill-specified source for your statement and you got a discussion of your crappy and ill-specified source. As said earlier in the thread, that's why PF insists on acceptable and well-specified sources.
My post was a question. I thought it was clear that I am a beginner at meteorology. The source was simply to provide some context. I am indeed grateful for the interesting discussion.
 
  • #35
physicsponderer said:
Would you care to expand on that?
At this point, I think it would make more sense to pass the conch to you, and ask you explain why - when you are directed to "very long contiguous streamers of cloud banks showing the circular interaction of air masses on the scale of thousands of kilometres, notably between temperate and polar latitudes" - you don't see that as "direct evidence of atmospheric circulation".

Alternately, what is the minimum you would reasonably expect to see in order to accept it as direct evidence of atmospheric circulation?
 
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  • #36
DaveC426913 said:
At this point, I think it would make more sense to pass the conch to you, and ask you explain why - when you are directed to "very long contiguous streamers of cloud banks showing the circular interaction of air masses on the scale of thousands of kilometres, notably between temperate and polar latitudes" - you don't see that as "direct evidence of atmospheric circulation".

Alternately, what is the minimum you would reasonably expect to see in order to accept it as direct evidence of atmospheric circulation?
Your statement was useful. I hadn't noticed those streamers, or rather, hadn't noticed how long they are, nor that their length does suggest atmospheric circulation. I meant, 'That's very useful, could you tell me a bit more about that?'. I've looked at that photo so many times over my lifetime, and I never thought properly about those streamers. Didn't really notice them at all.
Having said that, I think 'directly visible to the trained eye' would be more accurate than simply 'directly visible'.
 
  • #38
physicsponderer said:
I wonder why the streamers of cloud are concave to the southwest when the westerlies are concave in the opposite direction in https://en.wikipedia.org/wiki/File:Earth_Global_Circulation_-_en.svg ?
Sorry. Not 'concave' they are either rotating clockwise or rotating counterclockwise.

What we are seeing here is air masses in the southern hemisphere rotating clockwise, as expected:
1610250996938.png


Left pic: Northern hemisphere, Right pic: Southern Hemisphere:
1610251174301.png
BTW, Only the largest storms look like whirlpools. More typical storms look like commas with long tails. The head of the coma is the centre of the storm, so a comma whose head is clockwise from its tail is rotating clockwise, thus:
1610251627174.png
 
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  • #39
I thought 'atmospheric circulation' referred to circulation of air due to the Hadley cells, Ferrel cells, and/or polar cells, not air circulating around a zone of low pressure.
 
  • #40
physicsponderer said:
... air circulating around a zone of low pressure.
Well, it is atmosphere. And it is circulating. So...
 
  • #41
DaveC426913 said:
Left pic: Northern hemisphere, Right pic: Southern Hemisphere:
View attachment 275949
May I ask where you got these two diagrams from?
 
  • #42
physicsponderer said:
May I ask where you got these two diagrams from?
Google. I searched images for 'clockwise storms in southern hemisphere' or somesuch.
 
  • #43
DaveC426913 said:
Google. I searched images for 'clockwise storms in southern hemisphere' or somesuch.
I found them (I think) here at Roger Williams University website: https://rwu.pressbooks.pub/webboceanography/chapter/8-4-hurricanes/ which seems on the whole to be quite a useful source of knowledge for a meteorology beginner/amateur like myself.
 
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  • #44
physicsponderer said:
I found them (I think) here at Roger Williams University website: https://rwu.pressbooks.pub/webboceanography/chapter/8-4-hurricanes/ which seems on the whole to be quite a useful source of knowledge for a meteorology beginner/amateur like myself.
The book is focused mainly on oceanography, but anyway it looks interesting. Thanks for sharing.
 

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