Making It Rain

I have long noticed that in summer downpours, the heavy rain seems to begin so suddenly. It seems as if there are a few smaller drops of rain falling, the thunder and lightning starts and then all of a sudden, the heavy rain begins and it is like standing under Niagara Falls. I got to wondering about what factors could be involved in the sudden beginning of such heavy downpours.

Let's take a quick look at what happens when it rains. It can rain, at least to a moderate extent, from any sizable cloud, whether cumulus or stratus. But heavy downpours tend to come from those dark, towering cumulo-nimbus clouds that hold tremendous amounts of water.

Clouds are composed of vast numbers of water droplets that condense on dust particles in the air and hold together by hydrogen bonding. This bond occurs because water molecules are polar, one side of the water molecule is more negative and the other side more positive and the molecules thus line up end to end. When these droplets become so numerous that they collide with each other, they merge together into larger droplets that are too big to remain suspended in the air and they fall as rain, collecting other droplets as they fall.

But for heavy rain to begin so suddenly, there must be a factor that causes the droplets to begin to collide with each other at a very high rate. I say that this sudden beginning of heavy rain cannot be due to a weakening of some updraft that kept the droplets suspended in the air. Updrafts are stronger over cities than over rural areas because concrete and asphalt gain heat faster than land and if this were true, there would be significantly different rain patterns in cities in comparision with the sorrounding countryside and there is no evidence that there is.

The thought occurred to me that it is the shock wave created by lightning, which we hear as thunder, that jostles the closely packed water droplets in a dense cloud so that they collide and join into larger droplets that are too heavy to remain suspended in the air and which fall as rain. Lightning is the result of static electricity produced by the strong and close together updrafts and downdrafts in the cloud.

What better way is there to explain why heavy downpours seem to begin so suddenly after a few bolts of lightning? The microscopic droplets of water in a dense cumulo-nimbus cloud are in very close proximity to one another and it requires only the shock wave through the air, caused by sudden heating and expansion, to cause them to collide and join by hydrogen bonding so that they fall as rain.

So much effort has been put into creating rain artificially, particularly by China and Australia. The most common method thus far seems to be seeding the clouds with silver iodide using an aircraft flying above the cloud. This promotes cooling and causes more water vapor (vapor) to condense. However, such methods have had very limited success so far.

Why not craft an explosive charge attached to a balloon or rocket that can be sent into the cloud and will closely approximate the sound and shock wave of a loud thunderclap? This would be much simpler and less expensive than silver iodide seeding and would imitate nature in that it would jostle the closely-packed water droplets in a dense cloud into joining together by hydrogen bonding into larger droplets that will then fall as rain.