气旋活动对福岛核污染物扩散影响的模拟研究

基于拉格朗日粒子扩散模式FLEXPART-WRF,根据Stohl推导的日本福岛第一核电站核事故(下称福岛核事故)发生后40 d内的137Cs排放量数据,对核污染物在中尺度区域的扩散传输进行数值模拟研究,并选取近5年3次典型气旋个例(北方气旋、南方气旋和缓慢移动气旋)进行敏感性试验,以分析不同气旋系统对污染物扩散的影响. 结果表明:福岛核事故发生后,受中纬度西风带影响,核污染物主要向东部太平洋方向扩散；核事故发生后的5 d,受北方气旋和日本南部局地中尺度气旋2次气旋过程的影响,核污染物对日本本土部分地区影响较大,但影响时间不长. 典型气旋个例的敏感性模拟试验结果表明:北方气旋和南方气旋均可使核污染物对日本本土造成一定的影响,但由于气旋移动速度较快,影响日本岛的时间较短,沉降量也较小；当出现缓慢移动气旋影响日本和周边地区时,可致污染物影响日本岛的时间延长,并直接进入东亚大陆. 

Simulation Study of Extratropical Cyclone Activities on the Nuclear Material Dispersion from the Damaged Fukushima Nuclear Power Plant

In this study the Lagrangian particle dispersion model FLEXPART-WRF was adopted to simulate the nuclear radiation transport in the atmosphere for the crisis of the Fukushima Daiichi nuclear power plant, according to the emissions inventory of ¹³⁷Cs. Besides the simulation for the nuclear accident period, three simulations for the sensitivity were also conducted for three kinds of typical cyclone activity processes including the northern cyclone, the southern cyclone and the quasi-stationary cyclone to reveal the possible transport path of radioactive materials. The results showed that after the occurrence of the accident, the radioactive materials primarily spread toward the eastern Pacific Ocean under the effect of the westerlies in the mid-latitudes. In the first five days, nuclear contaminants produced a short-term but significant impact on the Japan Island under influences of two cyclone processes of a northern cyclone and a meso-scale cyclone in the south Japan. Since the sensitivity experiments of the typical cyclone processes, less deposition occurred in Japan for the fast movement of northern and southern cyclones. However, the quasi-stationary cyclone process can extend the residence time of the nuclear materials in Japan, and the radioactive contaminants can be driven into the East Asia Continent.