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Man-made rain to cool Shanghai's power demand
By Liang Yu (China Daily)
Updated: 2004-06-15 00:22

The city of Shanghai will resort to artificial rain to cool down the city and slow down a power demand that is outstripping the supply.

The man-made precipitation is part of local meteorological authorities' efforts to set up a long-term mechanism aimed to minimize losses caused by bad weather like prolonged heatwaves or heavy fog, officials said.

"We will conduct an artificial precipitation test soon in late June, if everything goes as scheduled," said Wang Jin, a publicity official of the Shanghai Meteorological Bureau (SMB).

To precipitate the rain, an airplane travels over the city to create seed clouds with a catalyst like salt, silver iodide or dry ice. Any of the three can induces rainfall and thus lower the temperature, said Wang.

If the test goes smoothly, the approach will then be used during the city's hottest summer days, which are expected to match the peak periods for power demand.

Shanghai suffered several power shortages last summer, when a unprecedented heatwave hit the city. For a record 40 days in a row,maximum temperatures stayed above 35 C.

Due to the soaring power demand at that time, power was even temporarily cut to some industrial sectors in a few cases.

Local meteorological authorities have forecast that this year the city will have up to 21 days when temperatures will exceed 35 C.

Though apparently much lower than that of 2003, it is still worth noting.

Normally, Shanghai has only about nine such days in a summer, according to Wang.

The country saw the first application of artificial precipitation as early as the 1950s. In most cases, it is used to bring relief to an area afflicted by drought.

In the 1990s, Shanghai used such artificial approaches to precipitate rainfall before the opening of East Asia Games and the Eighth National Sports Games.

According to Huang Jiaxin, director of the Shanghai Atmospheric Sciences Research Development Centre, artificial rainfall can help reduce affliction from natural disasters, reduce water shortages and improve local ecological environment.

The practice can boost rainfall by 5-20 per cent in a specific area, Huang said.

"As it is only applied in a limited certain area, it will have little influence upon the neighbouring areas," Huang said.

At the same time, man-made rainfall has little impact on the local environment, Huang added.

He made the remarks as concerns seemed to rise over the use of chemicals to create rain.

Some people fear that the chemicals used may hurt the environment.

The cost for one artificial rainfall in the city would be 4.7 million yuan (US$568,000), said local media reports.

Wang Jin, from the SMB, said most of the cost lies in the rent and operation fees of the plane as well as co-ordination expenses. The cost is paid by the city government.

"We think it would be worthwhile, if the investment can really bring the effect as expected, especially if it helps lessen the pressure on the local power supply," said Wang.

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