President Hu Jintao Makes It Rain

The strippers in Beijing are about to get wet

I’m sure that many of you have heard by now that the Chinese plan on using rockets at next summer’s Olympic games in Beijing in order to control the rainfall. The purpose behind this is two-fold. First of all, they want to make it rain before the games actually start in order to clean up as much of the air pollution as possible (in a related story, the Australian Olympic team has announced that they will arrive to Beijing at the last minute in order to minimize their athletes’ exposure to Beijing’s air pollution). Second of all, once the games actually do start, they want to keep the rain away.

So how does all this rocket business work? I decided to do some research to find out.

First, some background information.

Using data from this site and by doing some simple math, I have ascertained that the city of Beijing averages 25.36 inches of rain per year, the bulk of which comes during the summer months. That averages to 2.11 inches of rain per month. Not counting the summer months, however, the average monthly rainfall falls to a paltry 0.70 inches. Beijing and much of the rest of China suffer from drought conditions for the better part of every year. This has spurred China to create the largest rainmaking operation in the world [source].

The two main ingredients in rainmaking, also known as cloud seeding, are silver iodide and frozen carbon dioxide (aka dry ice) [source].

Silver Iodide (AgI) is what’s known as a nucleating agent. A nucleating agent is defined as a “substance with the ability to act as substrate for crystal formation by epitaxy, thus increasing the nucleation density. Improves crystallisation behaviour in processing…” [source]. Basically, what that means is that a nucleating agent is something that helps form crystals. Silver Iodide’s nucleating agent properties that make it ideal for cloud seeding were struck upon by a scientist in the employ of GE’s Research Lab named Bernard Vonnegut (older brother of one Kurt Vonnegut) in November of 1946 [source]. I’m TURRIBLE at chemistry, but I still tried looking up what it is about silver iodide that makes it a nucleating agent. That shyte was waaaay to technical and I couldn’t make heads from tails from any of it, but this simple entry on wikipedia tells me all that I’ll ever understand about this: “Silver iodide is highly insoluble in water and has a crystalline structure similar to that of ice, allowing it to induce freezing (heterogeneous nucleation) in cloud seeding for the purpose of rainmaking.” And for those of us who are curious, heterogeneous nucleation is “the formation of a bubble or of a crystal from a liquid…Nucleation normally occurs at nucleation sites on surfaces containing the liquid or vapour. Suspended particles or minute bubbles also provide nucleation sites. This is called heterogeneous nucleation” [source].

I myself know a little bit about dry ice. It’s carbon dioxide (CO2) in its solid, frozen form. It’s rather easily manufactured and also rather cheap. Other than that, I don’t really know much. Oh, and it’s really cold. Colder than zero degrees Celsius, which, as we’ll see later in wikipedia, is critical in the rainmaking business.

I lack the ability to put into my own words what happens when silver iodide and dry ice are dispersed into the atmosphere for the purposes of cloud seeding, so I’ll once again refer you to this wikipedia article for most of the details. The basic idea is that once they’re dispersed in the atmosphere, they’ll either induce freezing of surrounding water vapors (silver iodide) or they’ll use the surrounding water vapors to cause ice crystals to spontaneously nucleate (dry ice). Eventually, what forms precipitates out as either rain or as snow.

The Chinese have at their disposal 37,000 people, 30 aircraft, 4,000 rocket launchers and and over 7,000 artillery pieces in their quest to control the rain. Not that I’m some sort of weather expert or anything, but I doubt that they would bring them all to bear on Beijing for the Olympics, but they’re out there.

From what I’ve been able to gather by scouring various news-media articles is that in the time leading up to the Olympic games starting, Beijing’s weather manipulation office, headed by one Zhang Qiang, will use rockets to disperse silver iodide and dry ice into Beijing’s atmosphere in order to induce rain to wash away as much of Beijing’s air pollution as possible.

Once the games begin, meteorologists will be in contact with whoever will be out there, manning the guns. Their plan is to jointly hunt rain clouds and coax whatever moisture out of them that they can so as to prevent as much rainfall over Beijing as possible.

Of course, none of this is an exact science. The Chinese authorities will be conducting many tests to try and hone their technique. I have also heard that they are also considering banning a million or so cars from the streets to see what kind of effect that would have on clearing up pollution [source].

But, quoting Zhang Qiang from that USA Today piece, “But I can’t guarantee the ceremony (will be dry). If there is a big rainstorm, I have no way to stop it.”

I suppose now that we have a [somewhat] better understanding of how this rainmaking is supposed to work, all that’s left is for us to wait a year and see what, if anything, happens.