Glimmerjim wrote:I could very well be wrong about this, but it only makes sense to me that there would have to be enough moisture in the air above a certain area to even begin to think about causing rainfall by condensing the moisture or whatever they do. They could do it it 24/7 over the Australian outback and I don't think you'd add a drop.
And even if there is enough moisture there have to be the right conditions to make it rain.
The dew point is one way to express the amount of moisture. I've heard, but who knows if true, that the deserts of Iraq have consistently some of the highest dew points in the world. Meaning they have plenty of moisture in the air.
However, if there is not some driving force to take that moisture and raise it to an elevation where it is cooled below the dew point, I just don't see how they will be able to make rain. Once cooled below the dew point, then the moisture may start to condense, this is where the nucleation sites matter. I have no idea of the details of that part of the process works and how likely seeding is to enhance it.
That driving force can be a mountain. That's why you have a wet side and a dry side and all the seeding in the world won't keep the dry side from being dry. Also there are fronts with one air mass pushing over the top of another. Convective instability
is how you get the pop up thunderstorms that many of us see.
I don't understand enough to know when seeding might work, but it seems like those conditions are rare and more likely to help enhance things when rain is likely and rarely to make rain when rain was unlikely.
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