Why does the Earth have 3 general circulation cells?

[MClarkson]

instead of 2 or 4 or any other number? Is there an equation that specifically deals with this? For example Jupiter, with different rotation, insolation, a larger thicker denser atmosphere has many more circulation cells than we do.

 

[Aric Cylkowski]

According to http://en.wikipedia.org/wiki/Cloud_pattern_on_Jupiter, it is due to Jupiter's much greater Coriolis Effect.

 

[B Ozanne]

Well, technically aren't there 6 cells? 3 in the northern hemisphere and 3 in the southern?

 

[Tom Stefanac]

Hmmm...

6 in total yes, but I think we do only have 3 real circulation cells per hemisphere.

If you think Jupiter is bad, look at mars which has only 1 big Hadley cell if I recall correctly. A professor of astrological physics discussed this as a guest speaker in the atmospheric club 3 years ago at university. Although I think it is seasonal? One big cell in the winter and two in the summer or something like that.

About earth...

I would argue it is three main things.

1) Earth's tilt
2) Ocean size and amount of water
3) Coriolis

The tilt keeps the thermal cycle in balance, if we were tilted more we would probably have 2 cells during the winter, 3 or 4 in transitional seasons and 2 in the summer, per hemisphere.

The ocean keeps the ITCZ together and relatively uniform, if we had half the world as all land and the other half as water I can sure but things would be weird.

Coriolis pretty much creates the westerlies which make the cells form. If the earth was not spinning we would have just one big cell (or so I have been told by my met teacher once upon a time).

But I am not really sure, just going out on a limb here (probably wrong). We need someone who has been able to model this stuff. They would know for sure!