Government officials from Jilin City, in northeast China's Jilin Province, are using a special frost that has increasingly appeared on its trees since the building of a dam in 1942 to promote winter tourism.

They told a press conference in Beijing yesterday that, though the frost could not be guaranteed to appear everyday in winter, the frequency was high and predicted in daily morning forecasts.

After the Fengman Hydropower Station dam was built on the upper reaches of the Songhua River, the friction as it passes through the hot turbines keeps the water just warm enough to stop it from freezing more than 60 kilometers downstream, even in the bitterly cold winter.

In Jilin's winters, temperatures often drop to minus 20 Celsius degrees, turning other waterways into skating rinks. But on the Songhua, the temperature difference between the water and the air makes heavy white vapor rise.

If the vapor density, air pressure and wind speeds are within range, icy droplets freeze on the surface of tree branches along the riverbank, creating what to some look like crystalline, snow-white flowers.

Sun Yaoqian, a municipal government official, said that from December 15, 2004 to February 18 this year there were 38 days when the frost could be seen on Jilin's Wusong Island, and even in the city proper 11 such days were reported.

Every midnight, information is collected from sites around Jilin to produce the daily morning forecasts, available from the local weather authority (0432-4662724), tourist sites, radio (0432-4681053) and hotels.

Because the factors involved are complex, the forecasts can only be made on the same day.

Jilin, formerly called "Jilin Wula" (which means "along the river" in the Manchu language), is the second largest city of Jilin Province and is 1,100 kilometers from Beijing.

(China.org.cn by Wang Zhiyong, December 16, 2005)