If the Sahara is caused by the Hadley cell, it should ring the Earth like the Hadley cell, surely?

[DaveC426913]

This photograph:
https://en.wikipedia.org/wiki/File:The_Earth_seen_from_Apollo_17.jpg
is captioned :'Cloud formations in a famous image of Earth from Apollo 17 makes atmospheric circulation directly visible'

I see no such caption associated with any images on that page.

I see this:

"The Blue Marble" is a famous photograph of the Earth taken on December 7, 1972, by the crew of the Apollo 17 spacecraft en route to the Moon at a distance of about 29,000 kilometres (18,000 mi). It shows Africa, Antarctica, and the Arabian Peninsula.

 

[physicsponderer]

I see no such caption associated with any images on that page.

I see this:

"The Blue Marble" is a famous photograph of the Earth taken on December 7, 1972, by the crew of the Apollo 17 spacecraft en route to the Moon at a distance of about 29,000 kilometres (18,000 mi). It shows Africa, Antarctica, and the Arabian Peninsula.

You are correct. My apologies. You can see the photo with the caption if you scroll down on this page:
https://en.wikipedia.org/wiki/Hadley_cell . I have edited the post accordingly. Thanks for pointing that out.

 

[physicsponderer]

I wonder what that vertical motion chart https://en.wikipedia.org/wiki/Hadley_cell#/media/File:Omega-500-july-era40-1979.png would look like if it were not ' July average ' but for a particular instant.

'500 hPa vertical velocity (Pa/S) in July from ERA-40 reanalysis, 1979-2001 average.

Negative (blue) values represent rising air; positive (red) values indicate sinking air. This map is an excellent illustration of the Hadley cell.' says Wikipedia.

Also, my suspicion that the chart was chosen for it's close correspondence to the Hadley cell theory seems to have been confirmed by the last bit.

Edit by physicsponderer: It would be interesting to see what the chart looks like for a random month average, annual average, decade average, and some randomly selected instants.

 

[DaveC426913]

You are correct. My apologies. You can see the photo with the caption if you scroll down on this page:
https://en.wikipedia.org/wiki/Hadley_cell . I have edited the post accordingly. Thanks for pointing that out.

OK. Atmospheric circulation is pretty directly evident in that pic. Do you not think so?

 

[physicsponderer]

OK. Atmospheric circulation is pretty directly evident in that pic. Do you not think so?

It's not evident to me. Would you care to explain it?

 

[DaveC426913]

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.

 

[physicsponderer]

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?

 

[phinds]

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.

 

[physicsponderer]

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.

 

[DaveC426913]

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?

 

[physicsponderer]

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'.

 

[physicsponderer]

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 ?

 

[DaveC426913]

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:

Left pic: Northern hemisphere, Right pic: Southern Hemisphere:

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:

 

[physicsponderer]

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.

 

[DaveC426913]

... air circulating around a zone of low pressure.

Well, it is atmosphere. And it is circulating. So...

 

[physicsponderer]

Left pic: Northern hemisphere, Right pic: Southern Hemisphere:
View attachment 275949

May I ask where you got these two diagrams from?

 

[DaveC426913]

May I ask where you got these two diagrams from?

Google. I searched images for 'clockwise storms in southern hemisphere' or somesuch.

 

[physicsponderer]

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.

 

[lomidrevo]

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.