Comprehensive Analysis of Aircraft Artificial Precipitation on Stratiform Clouds in Spring over Hebei Province

Artificial seeding and detection on stratiform clouds,associated with horizontal seeding and vertical verification at several altitudes,was first performed by Hebei Weather Modification Office over central and southern Hebei according to specific cloud characteristics on April 19,2013.This paper uses airborne probe detection data,combined with real time synoptic,satellite,radar,air-sounding and precipitation data,to investigate technical indicators of artificial operations on stratiform clouds in spring over Hebei.The result shows that radar echo increased from 15 dBZ to 25-35 dBZ,and cloud top height,cloud top temperature,particle effective diameter and optical depth retrieved from satellite also increased during the cloud development.While the particle effective diameter,optical depth and liquid water path dropped sharply,and radar echo weakened during the cloud dissipation stage.Number concentration and water content of supercooled cloud particles ranged from 100 to 700 cm-3and 0.01 to 0.081 g·m-3,respectively,at the height of 3 177 to 5 723 m,where cloud particles mainly grew bigger to precipitation particles,which was a feasible seeding area.The strong radar echo center expanded while radar echo enhanced a maximum of 35 dBZ in the affected area where cloud developed after the seeding operation.Satellite retrieved parameters,such as cloud top temperature and optical depth,increased significantly compared with those in the contrast area.