Generally relief or topography is considered to be responsible for precipitation to occur working as a barrier for moisture bearing wind and having a vital role in hydrological cycle.
Dear Ijaz,
I am not sure I fully understand your question... For precipitations to occur, a number of atmospheric processes need to take place, and those, in turn, require some conditions to be fulfilled, such as the saturation of air with moisture, or the presence of condensation nuclei. Topography is a physical constraint that can enhance precipitations, not so much as a "barrier" but more as a mechanism to force air motion upwards (up the slope), which results in the cooling of the air and therefore in quicker saturation.
Note that if a mountain range were to suddenly "disappear", the precipitation patterns would be significantly different, but there would still be lots of precipitations anyway, possibly at other places and/or at other times.
In summary, mountains may "stimulate" precipitations (e.g., increase their frequency or their intensity) but they are not required: in fact, it rains a lot over the oceans, where there are obviously no mountains to start with...
If this does not answer your question, then please sharpen or rephrase your query. Best regards, Michel.
For precipitation 3 factors are necessary.
1. Water Vapour
2. condensation nuclei. (for condensing the vapor any substance like dust partical is required)
3. Temperature ( for condensation)
by the combination of these 3 factors precipitation can be take place by 3 ways...
1. Orographic barrier (which you mention): barrier force to rice the air, air temp. reduces as it moves up. and condensation take place)
2. merging of two air masses (warm lighter air mass rise on cold dense air mass so condensation take place)
3. Convection currents ( heated earth surface heats the air along with, it become warmer , lighter and start to rise. Cold air in upper atmosphere subside to replace the warm air at surface . such a way convection currents starts, when warm air rises it temperature start reducing and condensation take place)
this is very crude explanation of How precipitation occur. But you consider only one type.
Please refer the books..
1. General climatology by Chritchfield
2. The Atmosphere : Lutzen and turbok
3. Climatology : D.S.Lal
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