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Cloud seeding helps alleviate drought Hu also said that evaluation of the cloud-seeding effect is very difficult, especially for the operations aimed at mitigating drought disasters. Aircraft cloud-seeding operations in North China usually cover a large area, the target-regions are not fixed; therefore, the floating target-control area or multi-target-control area method has to be used. Hu said ground cloud-seeding operations have fixed target areas, and the historical comparison of rainfall is usually used for evaluation of the cloud-seeding operations. Physical evidence of the effectiveness of cloud seeding is obtained by monitoring cloud through radar. In some cases airborne observations show an increase of ice concentration and a gradual broadening of particle size after seeding. Intensification of the radar echo in seeded areas is observed in many cases. But the expert added "the main problem is that because rainfall is so variable from day to day and from place to place, it's incredibly difficult to tell if you've achieved anything or not." In order to try and settle the matter, scientists from the Chinese geological department are now studying soil sediments from the operation area for traces of silver iodide. "At present, cloud-seeding technology is still in its developing stage. Many scientific-technical problems have not been completely resolved. However, we do have the scientific tools and techniques to make any necessary advancements," Hu said. In order to resolve the key problems, the national PE research project has been initiated and the advantages of different institutions are to be joined together. Other applications Chinese scientists are also researching how to expand the technologies to decrease high-temperatures in cities, disperse fog, supress hail from ruining crops and reduce frost and air pollution. "Man-made efforts to influence the weather are an important way of using modern science and technology to reduce or prevent disasters, and are already receiving a high level of attention in our country," Qin Dahe, a top official with the State Meteorological Administration, said in a meeting in Beijing. "Cloud seeding or artificial rain-making, hail prevention and fog-dispersal techniques will also be used to help improve ecosystem and control forest fires, secure freeway transportation and the success of key social events like the Beijing 2008 Olympic Games and the 2010 Shanghai World Expo," Qin Dahe said during a national conference in Beijing aimed at co-ordinating such operations.
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