All large scale circulation phenomena are better understood in the vertical plane than in the horizontal plane.
Also temperatures say generally more and are more causal for large scale features than pressures. This has a reason - energy exchages are better described by temperatures than pressures.
I have always seen that people who start modelling climates by trying to locate high and low pressure zones generally struggle to get Something consistent because the causalities are confusing.
The monsoon engine in the vertical plane is quite simple, one needs :
- a large land body (at rather low latitude, say around tropics)
- a large ocean body
As the ocean body is large, it is not far from being isothermal throughout the year.
The land body on the other hand strongly oscillates (the larger the amplitude, the stronger the effect) so that half of the year its temperature is above ocean and half of the year below.
Assuming N hemisphere, in summer the air above land is hot so it rises (corollary is that we have a low pressure but this is irrelevant)
Then in high altitude it must go somewhere. If it goes towards the ocean (here is the difficulty because it is not easy to say where the high altitude air will go) then it will sink above the ocean (corollary is that we have high pressure there).
Then because of mass conservation, the loop must be closed and the wet cold air goes again towards land on ground.
The result is that when this wet air rises again above the heated land, it expands and précipitations occur.
In winter it is opposite. It is the same vertical loop but it rotates in the opposite direction.
All this are necessary conditions but afaik the sufficient conditions for a monsoon regime to occur are not clearly known. Apparently the shape of the land/continent and oceanic currents (or their absence) play a role so that this becomes quite complicated.
For mapping purposes I have always adviced that if you have a large land mass beside an ocean (preferably eastwards) around the tropics and want a monsoon, just put it there.
You will find nobody who would argue that there should be none because nobody knows
Originally Posted by Deadshade
All large scale circulation phenomena are better understood in the vertical plane than in the horizontal plane.
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