Analysis Of Precipitation Enhancement Effect Of Rocket Randomized Experiments Of Artificial Precipitation Enhancement

Drought has been endangering the agricultural and ecological environment of China.It is becoming more and more important to alleviate drought problems in some areas through scientific artificial precipitation.The evaluation of artificial precipitation enhancement effect is an important part of artificial precipitation enhancement.At present,the conclusion of precipitation enhancement effect obtained by random precipitation enhancement experiment is generally accepted in the world,but there is a lack of research on rocket random field experiment in China.In order to promote the development of artificial weather modification in China,the Weather Modification Center of China Meteorological Administration and relevant provinces jointly organized and implemented the randomization field test and effect test technology of ground rocket artificial precipitation in Shandong,Fujian and Hainan from 2014 to2020.This paper analyzes the design of trial scheme of the 7-year random field experiments of ground rocket artificial precipitation enhancement in the three provinces,and conducts a statistical evaluation of various methods on the precipitation enhancement effect of the three provinces based on the operation sample information and the ground rainfall station data,and uses radar-based data,reanalysis data and sounding data,the precipitation enhancement effects of’20140510’in Shandong Province,’20170411’in Fujian Province and’20170906’in Hainan Province were physically test.The main conclusions are as follows:Stratiform mixed clouds are selected as the operation objects in Shandong and Fujian experimental areas.The operation standards are as follows:The echo intensity of stratocumulus mixed clouds is≥25 d BZ,the area of echo intensity≥25 d BZ is more than 400 km²,the height of cloud top is≥6.0 km,and the thickness of negative temperature layer is≥1.5 km.The mixed stratocumulus and convective clouds were selected as the operation objects in Hainan experimental area.The operation standards are as follows:the echo intensity of the cloud system≥25 d BZ,the area of the echo intensity≥25 d BZ is greater than 100 km²（convective cloud）,400 km²（mixed stratocumulu）,the cloud top height≥6.0 km,and the thickness of the negative temperature layer≥1.5 km.A total of 218 rocket operation experimental samples were obtained in the three provinces during the seven years,including 67 in Shandong,58 in Fujian and 93 in Hainan.In the Shandong experimental area,for the experimental group 1,the relative precipitation rate was calculated by the single ratio method,the double ratio method and the regional regression analysis method,and the results were 53.33%（p=0.01034）,63.86%（p=0.003644）and 62.83%(t=1.7398>t_0.05=1.714,p<0.05),respectively.For the experimental group 2,the relative precipitation enhancement rate was calculated by the single ratio method and the double ratio method,and the results were 7.99%（p=0.3138）and 46.19%（p=0.01369）,respectively.In the Fujian experimental area,the relative precipitation enhancement rate was calculated by single ratio method,double ratio method and regional regression analysis method,and the results were 2.54%（p=0.03866）,12.72%（p=0.001052）and 21.86%（t=0.9263>t0.05=1.7398,p<0.2）,respectively.In the Hainan experimental area,the relative precipitation enhancement rate was calculated by the single ratio method and the double ratio method,and the results were 38.33%（p=0.04891）and 27.54%（p=0.006537）,respectively.The case“20140510”in Shandong Province belongs to the stratocumulus mixed cloud operation under the background of the updraft area in front of the upper trough,and the weather background and water vapor conditions are suitable for operation.The operation changed the precipitation flux and echo volume of the target cloud from a decreasing trend to an increasing trend,which promoted the increase of the vertically integrated liquid water and maximum reflectivity of the target cloud.The average differences of precipitation flux,echo volume,vertically integrated liquid water and maximum reflectivity of the target cloud and the control cloud after the operation were significantly increased compared with the differences that existed before the operation,and the operation had a positive catalytic effect.The case“20170411”in Fujian Province belongs to the stratiform mixed cloud operation under the background of shear line,and the weather background and water vapor conditions are suitable for operation.The rocket operation makes the precipitation flux,echo volume,echo top height,vertically integrated liquid water and maximum reflectivity of the target cloud change from decreasing to increasing.The differences of precipitation flux,echo volume and vertically integrated liquid water of target cloud and control cloud after operation were significantly higher than those before operation,and the operation prolonged the life history of target cloud.The case of Hainan Province“20170906”is a stratocumulus mixed cloud operation under the background of Hainan low pressure.The weather background and water vapor conditions are suitable for operation.The rocket operation increases the precipitation flux and echo volume of the target cloud,and slows down the decreasing trend of echo top height and vertically integrated liquid water.The differences of precipitation flux,echo volume,echo top height and vertically integrated liquid water between the target cloud and the contrast cloud after the operation were significantly increased compared with the average differences that existed before the operation.