层状云人工催化物理效应的数值模拟

对于自然云催化过程的数值模拟可以再现人工催化后云的宏微观物理响应特征，有助于提高对人工催化机理的科学认识、优化人工催化方案。本文在WRF（Weather Research and Forecasting Model）模式Thompson微物理方案中加入碘化银人工催化过程，对2018年河北省一次层状云催化过程开展数值研究。数值模拟结果表明，采用与实际催化过程相似的催化剂量，层状云降水个例催化后冰晶含水量、数浓度及地面降水显著增加。该次降水个例自然云中冰相粒子较少，自然云中冰相过程不活跃，数值模拟结果再现了降水个例催化后从过冷却到冰、雪晶含量明显增加的转变。相同催化剂量下，催化层厚度的减少提高了播撒率，进一步优化了催化效果，可见，应该在云中过冷水含量丰富的云区开展冷云催化作业。人工催化过程增加的冰晶通过凝华过程增长并自动转化为雪晶，雪晶增长下落过程中以凇附过冷云水增长为主。本次催化过程导致地面降雪显著增加。

Numerical simulation on the physical effects of stratiform cloud after artificial cloud seeding

The macro and micro physical responses of cloud after artificial cloud seeding can be reproduced by numerical simulation of natural cloud seeding process, which is helpful to improve the scientific understanding of artificial seeding mechanism and optimize the artificial seeding methods. In this paper, a numerical study on the stratiform cloud seeding in Hebei Province in 2018 was carried out by adding the artificial cloud seeding process of silver iodide into the Thompson microphysics scheme of WRF(Weather Research and Forecasting Model) model. The numerical simulation results show that the content of ice particles and surface precipitation of stratiform cloud precipitation are significantly increased by using the seeding dose equivalent to the actual cloud seeding process. In this case, there are few ice particles in the natural cloud, and the ice phase process in the natural cloud is not active. The transition from supercooled condition to an obvious increase in ice and snow crystal content after seeding is reproduced by numerical simulation. With the same seeding dose, the reduction of catalytic layer thickness improves the seeding rate and further optimizes the catalytic effect, indicating that the actual cloud seeding operation should be carried out in the cloud areas having abundant supercooled water. The ice crystals increased in the artificial catalytic process grow through the deposition process and automatically convert into snow crystals, snow crystals grow up by the riming of supercooled cloud water, resulting in the increase of snowfall on the ground.