热带暖底积雨云人工播撒吸湿性催化剂机制与效果研究

Drought often occurs in Hainan Island because of the precipitation unevenly distributed in space and time. Due to its location in the tropics, the height of zero-degree level is often above 5000m, and it is very difficult for the surface cold cloud operation system to launch the catalyst into the overcooled area. Local precipitation is dominated by tropical cumulonimbus clouds and low-pressure systems. The supply of water vapor is abundant due to monsoon. The warm cloud precipitation mechanism plays an important role in the precipitation process. Therefore, it promotes droplet collision and growth process, increase surface precipitation and improve the benefits of artificial rainfall enhancement by hygroscopic seeding materials into warm cloud. There are many technical limitations for the artificial broadcast of hygroscopic seeding materials, including the observation of flow cloud structure of the target cloud, lifetime of updrafts, timing and dose of seeding, and assessment of artificial rainfall enhancement effect. There is an urgent need to observe and study the flow field structure of cumulonimbus clouds, simulate the artificial seeding process, summarize the key technical methods for cloud seeding materials, and summarize the effects of cloud seeding after field experiments. This project intends to use a variety of observational data to analyze the tropical cloud precipitation mechanism, flow field structure and mobile development activities in Hainan Island; numerical model simulation of the sensitivity of hygroscopic seeding materials to warm-bottom tropical cumulonimbus clouds is performed to study the artificial rainfall enhancement technology; randomized field effect test to assess the effect of hygroscopic seeding materials.

海南岛降水时空分布不均，常常发生大旱。由于地处热带，零度层高度常在5000m以上，地面冷云作业系统很难将催化剂发射到过冷区。当地降水以热带积雨云和低压系统为主，受季风影响水汽供应充沛，暖云降水机制在降水过程中占重要的地位，因此通过在暖云底播撒吸湿性催化剂，促进液滴碰并增长过程，增加地面降水有助于提高人工增雨作业效益。人工播撒吸湿性催化剂作业存在很多技术限制，包括作业云的流场结构观测、上升气流的维持时间、播撒时机和剂量、人工催化效果评估等关键技术难题。因此迫切需要观测和研究积雨云的流场结构，模拟人工催化过程，总结优化人工播撒催化剂的关键技术方法，通过外场试验总结人工播撒后的效果。本项目拟利用多种观测资料分析海南岛热带云降水机理、流场结构和移动发展活动规律；使用数值模式模拟吸湿性催化剂对暖底热带积雨云进行敏感性数值试验，研究人工催化技术方法；开展外场随机化效果检验试验，验证吸湿性催化剂的效果。

国内积雨云人工催化作业常使用飞机、火箭和高炮等装备在云的上层过冷区播撒碘化银或者使用地面发生器在云的上升气流区燃烧碘化银焰条达到人工增加降水或人工防雹的目的。但目前，我们对于在积雨云暖区播撒吸湿性暖云催化剂进行人工播撒增加降水的研究尚少。本项目通过研究热带积雨云的流场结构、模拟人工催化过程、总结并优化人工播撒催化剂的关键技术方法，以及外场试验，来观察总结热带暖云人工播撒后的效果和物理参数响应程度。研究内容主要为以下四个方面：(1)暖云底热带积雨云发展演变规律及流场结构反演分析；(2)暖云底积雨云吸湿性催化剂人工催化机理；（3）使用云降水物理方案和人工催化模式模拟暖云底热带积雨云吸湿性催化剂人工催化的典型个例，优化地面发生器播撒优化作业技术；(4)随机化外场试验研究暖云吸湿性催化剂人工催化的统计效果和物理效果响应验证。