层状云中飞机人工增雨作业间距的研究

Investigation of Cloud Seeding Interval for PrecipitationEnhancement by Aircraft within Stratiform Clouds

利用数值试验方法,设计了4km,8km和20km三种飞机增雨播云间距方案,研究了不同间距对有效区域的影响。从结果分析发现,实际形成的播云线受水平风场输送作用,与设计的航线产生了偏离;不同播云间距形成的投影有效面积、有效作用时段不同,其时空分布及投影有效面积所对应的地面位置也不尽相同。另外,提出了增雨效益的数学表达式。效益分析表明,在相同作业条件下,8km间距的增雨效益比20km间距提高31%,比4km间距提高了23%,4km间距比20km间距提高6%,其物理原因主要是并合作用。最后,针对交叉和平行播云方案,提出了设计最佳播云间距的数学表达式。

Three cloud seeding intervals frequently used in precipitation enhancement by aircraft within stratiform clouds are designed to investigate their effects on effective range by using numerical simulation. The simulated seeding lines deviate from the designed line due to transport by horizontal wind fields. The different seeding interval leads to diversified projective effective area and duration, whose tempo spatial distribution and corresponding surface position are variable. Enlargement or reduction of seeding interval does not mean to simply and synchronously amplify the effective area and duration, but amalgamation of seeding lines can extend the effective duration. Also a mathematical formula of benefit for precipitation enhancement is developed. Under the same operational conditions, the benefit of 8 km interval is 31 percent higher than that of the 20 km, and 23 percent higher than that of the 4 km. Finally, a set of mathematical expression of seeding interval is formulated for cross and parallel seeding schemes from the view of physical cause.