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Abstract

With the support of Chinese Ministry of Science and Technology, we selected typical test areas in Chinese four provinces, designed scientific test schemes for the typical cloud systems, and implemented a 7-year (2014-2020) randomized precipitation enhancement project CREAPE. Totally 230 random test samples of cloud-seeding from CREAPE were obtained in the four provinces. The statistical test results of rocket operation samples are as follow. (1) For the rocket operation in Shandong experimental area, 45 random samples affected by southwest wind were statistically evaluated by single ratio method, double ratio method and regional regression analysis, and the rain increase rates were 53.33% (significance level p=0.01034), 63.86% (p=0.003644) and 62.83% (by t-test, t=1.7398>t_0.05=1.714, p<0.05), respectively; For the 16 random samples affected by west wind, the rain increase rates were 7.99% (p=0.3138) and 46.19% (p=0.01369) based on single ratio method and double ratio method, respectively, while the regression equation fails to pass the significance test due to too small sample numbers when evaluated by regional regression analysis. (2) For the rocket operation in Fujian experimental area, 57 random samples were statistically assessed using the three methods, and the rain increase rates were 2.54% (p=0.03866), 12.72% (p=0.001052), and 21.86% (t=0.9263>t_0.2=0.854, p<0.2), respectively. (3) For the rocket operation in Tunchang experimental area of Hainan province, 82 random samples were statistically estimated by single ratio method and double ratio method, and the rain increase rates were 38.33% (p=0.04891) and 27.54% (p=0.006537), respectively. Physical evidences by radar observation were shown in the three test areas.