基于RAMS／CFORS Ⅱ模式一次低空核试验放射性烟云扩散的数值模拟

Numerical Simulation of a Low Altitude Nuclear Explosion Test Radioactive Plume Diffusion Based on RAMS/CFORS Ⅱ Model

采用RAMS/CFORS Ⅱ模式模拟了一次低空核试验烟云的传输和沉降过程。CFORS Ⅱ模式是在RAMS/CFORS模式的基础上开发的,可用于对核试验放射性烟云长距离输送和沉降过程的模拟研究。模拟表明:对流层中低层的低压槽系统对本次低空核试验烟云的水平传输和垂直扩散起着重要的影响作用;烟云的长距离传输速度呈现出随高度递减而减小的趋势,在6000m以上,烟云在爆后48h即东移入海,6000m以下,烟云在中国大陆的扩散和沉降维持了5d以上;爆后2天内以大粒子沉降为主,其后以小粒子沉降为主,小粒子的放射性远小于大粒子,在爆后第4天,放射性沉降就减小了3个量级,而小粒子的沉降范围是大粒子的5倍以上。通过模拟和观测对比表明,模拟结果基本符合实际烟云的传输和沉降态势。

Transport and deposition processes of a low altitude nuclear explosion test plume were simulated by u sing RAMS/CFORS Ⅱ model. CFORS Ⅱ model implemented in RAMS/CFORS, can be used to simulate long-distance transport and deposition processes of nuclear explosion test radioactive plume. A good agreement was gotten through comparison between simulation results and observed data. And some other conclusions were found. The trough system on low-middle troposphere had played an important role in the horizontal transportation and vertical diffusion of this test plume. The velocity of plume long-distance transportation decreased with altitude, and the test plume above 6 000 m moved towards sea after 48 h and under 6 000 m, the diffusion and deposition processes of the plume were sustained beyond 5 d. During 2 d after test, deposition was dominated by big particles, but later fine particles seemed to be the main component of the deposition. The radioactivity of fine particles was much lower than that of big particles. On the 4th day after test, the radioactivity of deposition decreased about 3 levels, but the deposition area of fine particles was 5 times more than that of big particles.