I’d like to know if this theory of mine is correct or not please.
When a body of air containing clouds is blown from an area of lowland to an area of highland, the air pressure will increase. The increased air pressure will increase the condensation rate, so that bigger water droplets will form making it more likely to start raining. I’m assuming rain starts when the water droplets reach a certain size, so they become too heavy to be supported by the air currents.
I think this is an elegant theory, but unfortunately this doesn’t mean its correct. I’d welcome any informed opinions.
The damp air or clouds are forced higher by the change in ground level. The greater altitude results in a drop in temperature, meaning the air cannot hold as much moisture and causing greater condensation - this means that clear air can form clouds, clouds can become rain, and rain can become heavier rain (or snow).
Sorry Gorillaman, but your reply contains a common misconception. Cold air does not hold less moisture than warm air. See this link. Its a subtle point.
Still, thinking about it, your explanation that the clouds are being forced higher is what causes the increased condensation is probably correct, and likely to have much more effect than my explanation. So I’d like to re-phrase my question, would my theory have any effect? Or is it simply wrong - would the increase in air pressure not change the condensation rate significantly?
I think the pressure would increase, but probably by only a minute amount. A volume of air is being pushed into a smaller space, creating an updraught. Of course, the space is open at the top and sides, so this could only be a transatory effect.
Yes, I’d agree the drop in temperature is the real reason for increased condensation and therefore increased precipitation. Thinking about it in these terms, its looking increasingly likely my theory isn’t just flawed but is in fact plain wrong.
Air being forced up due to mountains decreases in pressure. Lower pressure is unable to hold moisture as well as high pressure. You get clouds and then rain.
On the downslope of a mountain range, the air descends and increases in pressure. The clouds go away. Hence, in the Pacific Northwest, the westest areas are on the front of the ranges, the driest are on the back.