intro to weather control

July 29, 2009

(credit: Wikimedia)

Fair weather cumulous clouds (credit: Wikimedia)

Even though it’s been around for over fifty years, the idea of controlling the amount of precipitation in an area with chemicals still seems quite futuristic to me. I know many ski resorts seed their environs for more fresh power and had heard stories of China’s preventing rain from its opening Olympic ceremonies last year, but this new report about China’s efforts to again ensure dry skies for next year’s Asian Games got me wondering just how cloud seeding (as it’s called) works. Here’s a brief discussion from my research:

The entire process revolves around the phases of water in clouds. Such weather control can either be used to promote precipitation (like rain or snow) or inhibit it (like rain or often hail).

The water vapor in clouds is very, very cold (well below its freezing point, called supercooled) due to its height in the atmosphere. The problem is that in order for the vapor to turn into liquid or solid droplets, it usually needs a seed or starting particle (natural dust particles usually serve this role). One of the most common seeding chemicals, silver iodide, which has a crystalline structure very similar to that of water, is used to start these water (or ice) particles forming in the cloud.

Other chemicals like dry ice (solid CO2, liquid nitrogen, or liquid propane) can be used to cool down the water vapor so much that it spontaneously forms small droplets without the need for a starter particle, so to speak.

When enough of these little droplets in a cloud form, they can start clumping together, and eventually the droplets become so large that the air currents can no longer support them, and they fall to earth as either rain, snow, or hail.

However, if you’re like China and want to avoid precipitation, you can seed the clouds just a little bit, and the ice particles produced actually form at the detriment of the natural water particles, thus reducing their size and likelihood of falling to earth.

It’s somewhat hard to measure exactly how efficacious cloud seeding actually is since there’s no way to do a counterfactual weather experiment, but it’s been successful enough for a number of countries, including the U.S., China, Russia, and Australia, to have used it at one point or another (China’s the most aggressive at it).

For those of you who are a bit wary of dropping chemicals like silver iodide into the sky, it seems that in the amount they’re currently being used, the health and environment impacts are negligible.

As many of you may know, there’s talk of creating more clouds in the atmosphere by either spraying water droplets up from the sea with vast fleets of autonomous sailboats or dropping seeding chemicals from the sky as previously discussed. It’ll be interesting to see how this last ditch option changes (or doesn’t) as our understanding of weather control improves.


One Response to “intro to weather control”

  1. T.V.Rama Rao Says:

    see the following web sites for more details as presented by prof.T.Shivaji Rao,of Gitam University, an international expert on cloud-seeding:
    ontact us for more detailed information,if needed
    T.V.Rama Rao.M.Com

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: