cloud seeder       
noun [ C ]  environment specialized uk/ˈklaʊd ˌsiː.dər/ us/ˈklaʊd ˌsiː.dɚ/
 (为人工降雨而)进行云催化的人(物质),实施云种散播的人
a person, organization, or device that spreads substances such as certain chemicals in clouds, in order to try to make them produce rain, or more rain
  To cloud seeders, the chilly mist is a promising source of rain. 对进行云种散播的人来说,寒冷的雾气是一个很有希望的雨源。 
 Farmers, ranchers and power companies hire their cloud seeders. 农场主、牧场主和电力公司雇用了实施云种散播的公司。 
 - More examples
 - Cloud seeders have to start with a cloud that shows at least the promise of rainfall.
 - Cloud seeders use silver iodide - a chemical whose structure happens to resemble that of ice crystals - on which supercooled water will condense into snow.
 - For more than 50 years, cloud seeders have been cranking up smoke machines and flying through clouds.
 - China is the world's leading cloud seeder, using an array of methods to disperse chemicals into cloud layers.