What effect does elevation have on rainfall?

Question

What effect does elevation have on rainfall?

Answer 1

Rain bearing clouds from warm seas (mid-latitudes 25 to 35

degrees on western continental margins are avoided) when they blow onto land and encounter rised mountains get cooler to form water drops that precipitate as rain. This gives rise to profuse, lush vegetation and rainforest in tropics. All  river systems with minor exceptions originate on mountain slopes. The mightier rivers flow east or have a trend towards that, except  Nile (northward) & Congo (westward).

Answer 2

Air is cooled as it is forced upward, and cooler air can hold less water. Orographic precipitation is caused when wet air masses are forced up over mountain ranges. For example, warmer humid air passing off the Pacific ocean is  cooled as it is forced up and over ranges like the Cascades in Washington and Oregon. The higher it goes, the cooler it gets on average, and thus there is rainfall. In the case of the Cascades 100 or more inches per year in places.

By the way, huge rivers flow north (the Ob and Lena in Russia or the Mackenzie in Canada), south (the Mississippi), and west (the Yukon, the Columbia, and the Rhine) as well as east. The direction of flow has almost nothing to do with orographic rainfall sensu strictu and everything to do with the plate tectonics that formed continents and thus the distribution of high elevation areas.

Answer 3

The only properties which consistently show a statistically significant elevation effect are the mean rainfall intensity and the proportion of wet intervals.   Rainfall at upper elevations can be as much as 70% more than that on the lower elevations in summer.