A numerical simulation study on a convective cloud artificial rain enhancement seeding experiment in Gutian, Fujian Province

doi:10.11755/j.issn.1006-7639-2025-05-0770

Abstract

Abstract:

Convective cloud systems, characterized by complex and variable structures, are key targets for atmospheric water resource exploitation through artificial rain enhancement in the South China. Reasonably evaluating the seeding operation process through numerical models and further studying their catalytic mechanisms is a necessary approach to establishing and improving seeding operation techniques, and it is also an effective means to assess the actual effects of artificial rain enhancement operations. In this study, based on the Weather Research and Forecasting (WRF) model coupled with a silver iodide (AgI) seeding module, a catalytic simulation was conducted for the case of the artificial rainfall enhancement experiment in Gutian, Fujian Province on May 4, 2021. The catalytic mechanism of AgI nucleation, the impact of the catalysis on the macro and micro characteristics of the cloud system, the precipitation mechanism, and the evaluation of the rainfall enhancement effect were analyzed. Numerical simulation results indicate that the dispersed AgI particles spread in a band-like patterns within the clouds. During the initial catalytic stage (09:00-11:00 UTC), the increment of ground precipitation increased slowly. Then (from 11:00 to 13:00 UTC), the precipitation increment increased significantly and showed sharp fluctuations, after 13:00 UTC, the increment of precipitation was mainly negative. Deposition nucleation was identified as the dominant AgI activation mechanism, sustaining effective catalysis for approximately 40 minutes. After AgI was dispersed, it mainly increased the number concentration of ice crystals through sublimation nucleation (by 3 to 9 particles per liter). The majority of the increased ice crystals transformed into snow crystals, and then the melting of these snow crystals increased the mass concentration of raindrops in the cloud. The impact of seeding persisted for about four hours, resulting in an absolute increase in precipitation ranging from -0.78 to 1.24 mm, the rainfall enhancement rate was approximately -8.3% to 12.1%, and the total precipitation increase was 4.64×10⁵ tons. The rainfall enhancement effect was significant.

Key words: mesoscale cold cloud seeding model, rainfall enhancement, effect evaluation, silver iodide seeding

摘要：

对流云是南方人工增雨开发利用空中云水资源的重要对象，结构复杂多变；通过数值模式合理评估催化作业过程，进而研究其催化机制，是建立和改进催化作业技术的必要途径，也是评估实际人工增雨作业效果的有效手段。利用耦合了碘化银（AgI）催化的WRF（Weather Research and Forecasting）模式，对2021年5月4日福建古田人工增雨随机化试验个例开展催化模拟，分析AgI核化机制、催化对云系宏微观特征、降水机制的影响以及增雨效果评估。结果显示，AgI播撒后呈带状扩散，催化前期（09：00—11：00）（世界时，下同）地面降水增量缓慢增加；随后（11：00—13：00）降水增幅加大并出现剧烈波动；13：00后降水增量以负值为主。AgI主要核化机制为凝华核化，核化持续约40 min。AgI播撒后主要通过凝华核化使冰晶数浓度大幅增加（增量约3~9个·L^-1），增长的冰晶大部分转化为雪晶，再通过雪晶融化增加云中雨滴质量浓度。此次过程催化影响时间持续约4 h，催化部位绝对增雨量约-0.78~1.24 mm，增雨率约-8.3%~12.1%，总降水增量为4.64×10⁵ t，增雨效果显著。

关键词: 中尺度冷云催化模式, 人工增雨, 效果评估, 碘化银催化

CLC Number:

P481

XIE Zuxin, LIN Wen, LI Dan, HUA Shaofeng. A numerical simulation study on a convective cloud artificial rain enhancement seeding experiment in Gutian, Fujian Province[J]. Journal of Arid Meteorology, 2025, 43(5): 770-781.

谢祖欣, 林文, 李丹, 花少烽. 福建古田一次对流云人工增雨催化试验的数值模拟研究[J]. 干旱气象, 2025, 43(5): 770-781.

Figures/Tables 12

Fig.1 The WRF model domain configuration

Fig.2 Microphysical processes in the Thompson scheme

Fig.3 The distribution of observed (a) and simulated (b) precipitation from 00:00 May 4 to 00:00 May 5 in 2021 in the d03 area, and the hourly evolution of precipitation in the d03 area (c) and the testing area of Gutian (d) (The red triangle indicates the location of the operation point)

Fig.4 The evolution of radar composite reflectivity observed （a， b， c） and simulated （e， f， g） from 08：00 to 10：00 on May 4， 2021， and the observed （d） and simulated （h） reflectivity profiles along the purple line segment in figure 4（b）（Unit： dBZ）（The purple line segment in figure 4（b） indicates the direction of AgI seeding and diffusion）

Fig.5 Schematic diagrams of actual seeding path (a) and simulated seeding grid (b)

Fig.6 The mass concentration （the color shaded， Unit： 10-3 μg?kg-1） and movement path （the arrow direction） of AgI after its dissemination from 09：10 to 09：30 on May 4， 2021 （a）， and the natural cloud precipitation （b， Unit： mm）， ground precipitation increment （c）， precipitation increment （d， Unit： mm）， and rain enhancement rate （e， Unit： %） after catalysis from 09：00 to 13：00 May 4， 2021 （The red triangles denote approximate locations of the artificial rain enhancement operation site， the same as below； The rectangular box indicates the seeding influence area）

Fig.7 The distribution of water condensate in the cloud （the color shaded， Unit： kg?m-2）， the vertical accumulation of supercooled water （blue isolines， Unit： kg?m-2）， and the mass concentration of AgI （the red shaded， Unit： 10-3 μg?kg-1） during the AgI seeding nucleation period on May 4， 2021 （a） 09：00，（b） 09：10，（c） 09：20，（d） 09：30

Fig.8 Vertical profiles of mass concentration （the gray shaded， Unit： 10-3 μg?kg-1） of AgI， ice crystal number concentration （pink isolines， Unit： particles·L-1）， vertical velocity （blue isolines， positive values indicate updrafts and negative values indicate downdrafts， Unit： m·s-1）， air temperature （red isolines， Unit： ℃）， and ice surface supersaturation water vapor mixing ratio （the color shaded， Unit： g?kg-1） during AgI deposition， nuclearization period on May 4， 2021 （a） 09：00，（b） 09：10，（c） 09：20，（d） 09：30

Fig.9 The changes of the nuclearization efficiency of AgI for the three nuclearization mechanisms from 09：00 to 13：00 on May 4， 2021

Fig.10 Time-height evolution of number or mass concentration of the hydrometeor contents in natural cloulds (blue isolines) and their increments (the color shaded) after seeding (a, b, c, d, e), and vertical velocity (isolines) and its changes after seeding (f) from 09:00 to 13:00 on May 4, 2021

Fig.11 Variations of 10 min natural precipitation （a） and microphysical process transformation rates of raindrop source and sink terms （b） in the seeding influence area from 09：00 to 13：00 on May 4， 2021

Fig.12 The changes of micro-physical processes source and sink terms in clouds after seeding from 09:00 to 13:00 on May 4, 2021 (a) raindrops, (b) cloud droplets, (c) snow crystal, (d) water vapor

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