The Chinese capital is cold but dry in winter, with little cloud cover and only a couple of dustings of snow. So people were more than a little surprised when on November 19th, snow was general over Beijing, with 10 cms (4 ins) accumulating in central nd eastern parts, closing the city's main airport for several hours.
The forecast had been for light snow only. So what had happened?
Yesterday we found out, courtesy of the official China Daily. This was a man-made snowfall, engineered by the "Weather Modification Office" of the Beijing Meteorology Bureau, it revealed. It was the first successful cloud-seeding experiment in six attempts over two years to produce a heavy snowfall in a city plagued by a water shortage.
This is how they did it: when clouds began to gather on November 19th, officials from the bureau spread out over the city to release balloons into the air, each filled with 5 grams of silver iodide, according to Mr Qin Changhue, chief engineer at the Weather Modification Office. At 2,000 metres a burning fuse on each balloon ignited a flare which scattered an estimated 500,000 billion artificial ice crystals over the clouds. These drew moisture from the vapour to form snowflakes. The weather men were delighted with the success of the experiments, which Mr Qin said were designed "to increase natural precipitation in Beijing, which has long been plagued by water shortages and droughts". Each snowfall in Beijing in recent years averaged two to three millimetres and heavy snow is very rare, he said.
His delight was not shared by passengers on 56 incoming flights which were diverted from Beijing to Tianjin and were stranded there because of closed highways. Last week the clouds reappeared and snow was forecast once more, but it turned out to be the usual dusting before clear skies returned. Had the balloons failed? No, said the Weather Modification Office. A foreign dignitary was due in Beijing that day and the aviation administration vetoed another cloud seeding, worried that the airport might have to be closed again. It all proves once again the value of high-level contacts in China. They can stop the snow for you, if you are important enough - or even manufacture a white Christmas with communist snow.