Technical Methods Study And Cases Analysis On The Testing Of Convective Clouds Seeding Effects In Yangtze-Huaihe Region

This paper summarizes the testing methods of convective clouds seeding effects at home and abroad, then improves the regional historical regression statistical testing method from choosing target areas and control areas, selection of seeded samples and historical samples as well as considering the conditions of statistical test algorithm for the specific application to test the convective clouds seeding effects in Yangtze-Huaihe region; furthermore,develops a physical testing method with identification and track of convective clouds making use of Doppler Radar original echo and optimizes from identifying and tracking seeded units, objective selection of control units, choosing the physical parameters of radar echo, comparative analysis of change of physical parameters before and after operations between seeded units and control units to make it more suitable for evaluation of convective clouds seeding effects of in Yangtze-Huaihe region.Based on daily rainfall data of national ground stations of Anhui Province and SA Doppler Radar data covering operation areas, this paper makes some cases ananlysis on the testing of convective clouds seeding effects in Yangtze-Huaihe region in June to August 2012 and 2013 with combination of regional historical regression statistical analysis and physical test method using Doppler Radar identification and track of clouds seeding effects, the following conclusions:(1) The case on June 28 to 30, 2012 under subtropical high peripheral synoptic situation, had a statistical testing result of 37.20 mm in absolute rainfall and 65.17% relative to rainfall, with a significance level α=0.0904. Physical testing qualitative analysis of seeding effects of the two convective cloud units from this case indicated that the two seeding operations in Yongqiao District did not grasp the good opportunity of seeding, the first cloud seeding suppressed the weakening trend of seeded unit, and the seeded unit splited at about 20 minutes after the second seeding, therefore did not have the prerequisites for further development of convection, resulting in a not obvious seeding effects. The seeding operation in Sixian which had a good opportunity changed the situation of physical parameters continueing decrease of seeded unit, following various of physical parameters increasing significantly compared with control unit, promoted the development of convection once again and extended the lifetime of seeded unit, bringing significant effect of precipitation enhancement.(2) The case on August 9 to 10, 2012 under typhoon inverted trough synoptic situation, had a statistical testing result of 21.94 mm in absolute rainfall and 73.82% relative to rainfall, with a significance level α=0.0954. Physical testing analysis of convective cloud unit seeding effects with rocket operations of two different operating points from this case indicated that, because of strong local, complexity and frequent changes and other features about convective clouds, the role of contrastive analysis of control unit selected within radar range was not obvious; But combining the radar echo in operations, physical parameters of target unit had a slow development,and the target unit had a trend of merging with neighboring small units before operations. So the target unit merged and developed rapidly after the first seeding. After the twice seeding, the target unit had a further development of convection as well as a rapid increase in physical parameters, with a significant positive effect.(3) The case on July 18-19, 2013 under low groove of North China synoptic situation, had a statistical testing result of 24.50 mm in absolute rainfall and 63.16% relative to rainfall, with a significance level α=0.2829. Physical testing analysis of once seeding effects of convective cloud unit indicated that, the seeding operation was carried out at a good point, then physical parameters of seeded unit experienced two consecutive increases after seeding, having a more positive deviation comparing with control unit. But the seeded unit had a trend of amalgamation before operation, therefore this seeding operation had a role in convection development of seeded unit, but less obvious.The statistical testing analysis of above three cases is more than 50% relative to rainfall, and is consistent with the actual weather conditions before and after operations; except that statistical evaluation results of the third case had a poor significance, the other two cases had a good significantce. Physical testing qualitative analysis of seeding effects of convective cloud units from the three cases shows that the suitable point and position of clouds seeding are very important; Clouds seeding could enlarge physical parameters’ positive deviations of seeded units comparing with control units, promote further development of convection in seeded units, and extend the life span of convetive clouds with more precipitation to land; the physical testing results are similar to the statistical evaluations. In summary, technical methods on the testing of nonrandomized convective clouds seeding effects in Yangtze-Huaihe region are feasible, which combine statistical evaluation method with physical testing analysis.