Cloud Seeding Meets the Press (again): No Snow for Moscow 10.20.09

Earlier this month, The Mayor Yuri Luzhkov of Moscow hired the Russian Air Force to conduct chemical cloud spraying operations in hopes that no snow will fall within the city limits during the winter. Amongst the word from Moscow were sparked interests in cloud seeding around the world. It was reported that Moscow often hires the Russian Air Force (Time Magazine, Associated Press, et al.) to regularly perform cloud seeding activities.

The city has been hard hit by recession and the costly history of snow removal. In a huge initiative, the city says it hopes to reduce cost by preventing snow fall using cloud seeding as a resort to cost reduction. Although it is possible to better budget, address other critical issues that need attention in Moscow, it seems city officials are backing the anti-snow effort.

Russia and China are not the only countries interested in cloud seeding. The United States is currently involved in several research projects which focus on cloud seeding as a means of weather modification. In fact, there is a significant history of cloud seeding experiments.

Background on Cloud Seeding
To seed or not to seed, that is the question? It is possible for humans to modify the atmosphere on purpose or by accident. Usually, the more major producers of atmospheric modification activities are the people who are cloud seeding. The suggested purpose of cloud seeding is usually to enhance rainfall amounts, snowfall, to interfere with microphysical cloud characteristics, for example hail suppression, etc. We must be careful either way to avoid unnecessary air pollution.

Cloud seeding gained notoriety in the 1940's when the idea of using airplanes to inject silver iodide to mimic ice nuclei became a possible idea for weather modification. The idea was to supply more condensation nuclei to thus further increase general nuclei availability which in return increases the potential for falling snow or raindrops depending on temperature profiles. Seeding of any clouds require super cooled water colder than 0 degrees Celsius. Substances such as silver iodide (crystalline structured similar to ice) will help to induce freezing. In mid-latitude cloud structures, the vapor pressure is lower over water than over ice thus become heavy enough to fall as rain from clouds that without the availability of liquid droplets naturally formed would not produce rain fall. There are different types of seeding. For example dynamic seeding often used in tropical clouds utilizes latent heat released by the freezing process, thus causing further buoyancy, resulting in more convergence, stronger cloud growth and precipitation. The more modern technique for cloud seeding is the use of hygroscopic particles such as sodium chloride which help create substantially larger raindrops, increase coalescence, etc.

The argument over whether cloud seeing is effective or not continues. Both sides of the argument have valid evidence showing some support in favor of cloud seeding and obviously reasons why it is not effective or may be harmful. One major disadvantage over the entire argument of whether it works or not is due to the fact it is difficult to measure the difference between no-seeding (natural) and seeding (man-made) effects due to spatial atmospheric variability. Project StormFury 1950-1970 seeded several hurricanes, but could not effectively measure any change, result, or difference at all. Simply put, it's hard to argue either way because major efforts have failed to yield absolutely certain results of cloud seeding, show there is a difference before/after weather events for any given location, time, space, etc.

Research continues even to this day, even inside the United States (NCAR/Wyoming, et al.). "Static mode" cloud seeding may increase rainfall with the addition of ice crystals (silver iodide, dry ice, etc) into cold clouds. "Dynamic mode" cloud seeding increases rainfall by enhancing vertical building of cloud structure thus is able to possibly create more rain through vertical cloud growth processes using larger number of ice crystals versus less in static mode techniques. Research has indicated clouds with low concentrations of cloud condensation nuclei were more likely by means of collision-coalescence to produce more rain.

Cloud Seeding & Society
Many are unfamiliar with cloud seeding and probably are not aware that this occurs in our country. Cloud seeding can be viewed as an atmospheric research experiment. Hopefully, our researchers will operate carefully with due consideration to our atmosphere, the possible implications their activities may have, and the safety of our citizens. We must be careful as well since chemicals, compounds, or any substance can possibly accumulate on our lawns, roofs, farmland, etc. So far, it is said that traces of these substances from cloud seeding on the ground were not at toxic levels (above normal).

In the past, overseas for example, there was a some what of a humorous and dangerous outcome to a Russian cloud seeding operation. In Moscow (Russia), June 2008, it was reported that Russian air force planes dropped a 60lb sack of cement which fell on a suburban home causing some damage (thankfully no injuries). Other citizens around the world were concerned about air pollution and the possibility of unwanted atmospheric side effects.

Authored by Ben Alonzo/StormSector

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