By Katia Moskvitch
Cloud seeding on days of celebration has been routine
Standing by an open hatch on a Russian military plane high up in the sky is tricky.
All the more so when your job is to "seed" clouds, shovelling chemicals outside to cause rain.
These seeded clouds never make it to Moscow, where millions are enjoying a nice sunny holiday. Or where guests might be dancing at a wedding under the clear blue sky.
Some might think that controlling the weather sounds a bit like science fiction.
But military pilot Alexander Akimenkov doesn't think so.
He has seeded clouds over Moscow on important state holidays for many years. He says the Russians use two different methods to try to drive the rain away.
"Either there's a special machine that spits out silver iodide, dry ice or cement into the clouds, or a hatch opens and a guy with a shovel seeds the clouds manually," he explains.
"As soon as the chemicals touch the cloud, a hole appears. It becomes bigger and bigger, and it either rains right there and then or, if the clouds aren't very dense, they disperse without any precipitation."
The Russian government has used rain prevention methods since Soviet times, seeding clouds for major celebrations three times a year - Victory Day, City Day and, more recently, Russia Day.
There are also private companies that for some $6,000 per hour say they can guarantee sunshine on your wedding day - or for any other private party.
HOW CLOUD SEEDING WORKS
1. Silver iodide is fired into cloud using flares on planes or from the ground
2. Water droplets then attach to these particles
3. They fall as snow if surface temperatures are below or near freezing, or as raindrops at warmer temperatures
4. Heat released as the droplets freeze boosts updrafts, which pull more moist air into the cloud
Despite the use of the cloud-seeding technique, many scientists remain sceptical of its effectiveness
Many ecologists agree that these techniques, also used in many other countries for irrigation purposes, do not pose much of a threat to the environment or people's health, as the period of active influence on the clouds is very short.
But when Moscow's mayor Yuri Luzhkov suggested the technique could shift the winter snow outside the capital - and therefore save more than $10m in snow-clearing costs - many felt the city authorities were going a bit too far.
Alexey Yablokov says winter snow is vital in Moscow (Photo: Y. Kotlyarenko-Shukhman)
Even if the idea might appeal to Moscow drivers, tired of constant traffic jams - especially bad in snowy conditions - it has stirred concerns among local ecologists.
"Millions of tonnes of snow diverted from Moscow will create chaos in the areas where it is forced to fall and might even lead to the collapse of bridges and roofs," said Alexei Yablokov, one of Russia's leading environmentalists, who was ecological adviser to former President Boris Yeltsin.
Besides, a lack of snow in Moscow would cause many problems in the capital itself, he said.
"Why do we need snow in Moscow? Snow on the ground helps the roots of trees to survive during severe frosts. If there's no snow, lots of vegetation - trees, bushes - will die.
"Snow also cleans the atmosphere very effectively. If there's nothing to clean the Moscow atmosphere, many people will die - there will be tens or even hundreds of additional deaths," explains Mr Yablokov.
But Valery Stasenko from Roshydromet - the Federal Service of Hydrometeorology and Environmental Monitoring - calls these concerns groundless.
"It is stupid to say that there won't be any snow in Moscow. If there is some five centimetres of it, it's absolutely fine, but there is a limit when all the transport just stops," he said, adding that the aim of winter cloud-seeding would not be to get rid of snow, but to control its level, not letting it go over this maximum limit.
The planes will be out only occasionally, said Mr Stasenko, to prevent major snowfall that happens on average three or four times a month. Thus it will cost a lot less than using snowploughs that are out most days of the winter.
Moscow's mayor raised the possibility of seeding in the winter
"Besides, the idea didn't come to the Moscow mayor from nowhere, it is based on facts. In the early 1980s, back in the Soviet period, there was a special service to limit snowfall over Moscow. It stopped working during perestroika [Gorbachev's reforms], when money became scarce," Mr Stasenko said.
"Some eight to 10 planes had to find clouds with the most precipitation and spray them with crystallising chemicals.
"Not all water vapour in the atmosphere turns to precipitation, and for the snow to fall, water vapour should concentrate on ice crystals first. So we were making snow fall before it reached Moscow and this work reduced the amount of snow in the capital by 20, 30 and sometimes 40%."
And even though this winter is over and the snow in Moscow will soon disappear naturally, scientists at the Central Aerological Observatory of Roshydromet have been working for months trying to come up with new, improved techniques of winter cloud-seeding.
They refused to explain the essence of their work. And this secrecy raises important environmental concerns, says a climate specialist from the Russian Academy of Sciences' Department of Earth Sciences, Nina Zaitseva. She believes that even with raincloud seeding, much depends on luck and coincidence.
She is sceptical about the current research and the state's past or present ability to effectively seed winter clouds.
"I don't think there will be good results - dry substances are not able to have any noticeable reaction with ice particles. But if they decide to seed winter clouds with a liquid, they should first and foremost think about the ecological consequences," said Dr Zaitseva.
Regardless of the Moscow authorities' final decision on snow cloud seeding, Russia remains one of the few nations where weather control is more than using anti-hail cannons and battling droughts.
So if you want to visit Moscow and don't fancy rain, go there on one of the three precipitation-free holidays.
And if you want to ensure your wedding day is dry - it might just be possible to make it happen.