The Extra-Area Effect in 71 Cloud Seeding Operations during the Winters of 2008–14 over Jiangxi Province, East China

Effects of weather modification operations on precipitation in target regions have been widely reported, but little is specifically known about the downwind (extra-area) effects in China. We estimated the extra-area effect of an operational winter (November–February) aircraft cloud-seeding project in northern Jiangxi province in eastern China using a revised historical target/control regression analysis method based on precipitation data for winter. The results showed that the overall seasonal average rainfall at the downwind stations increased by 21.67% (p=0.0013). This enhancement effect was detected as far as 120 km away from the target area. Physical testing was used to compare the cloud characteristics before and after seeding on November 29, 2014. A posteriori analysis with respect to the characteristics of cloud units derived from operational weather radar data in Jiangxi was performed by tracking cloud units. The radar features in the target unit were enhanced relative to the control unit for more than two hours after operational cloud seeding, which is indicative of the extra-area seeding effect. The findings could be used to help relieve water shortages in China.