利用离散偶极子近似法(DDA),研究了等效半径Re在0.8 mm范围内的柱状和片状冰晶在不同空间取向、温度和尺度比时,对94 GHz雷达发射的水平偏振波产生的后向散射,并讨论了等效雷达反射率因子Ze随粒子谱中值直径及冰水含量的变化。结果表明,温度对后向散射效率的影响较低,空间取向对后向散射效率的影响与粒子大小和形状有关。当雷达波垂直指向天顶,在冰晶粒子等效半径Re<0.8 mm时,水平取向冰晶的后向散射效率比随机取向大,粒子越偏离球形,差别基本上越大;在同一取向时,粒子越偏离球形,后向散射效率基本上越大。在一定冰水含量下,取向、形状和冰晶谱的形状参数对Ze的影响和粒子谱中值直径有关;对于垂直指向的雷达,如果将六角形冰晶等效为等体积球形冰晶,当粒子较大(0.4 mm
Storm identification and tracking based on weather radar data are essential to nowcasting and severe weather warning.A new two-dimensional storm identification method simultaneously seeking in two directions is proposed,and identification results are used to discuss storm tracking algorithms.Three modern optimization algorithms (simulated annealing algorithm,genetic algorithm and ant colony algorithm) are tested to match storms in successive time intervals.Preliminary results indicate that the simulated annealing algorithm and ant colony algorithm are effective and have intuitionally adjustable parameters,whereas the genetic algorithm is unsatisfactorily constrained by the mode of genetic operations.Experiments provide not only the feasibility and characteristics of storm tracking with modern optimization algorithms,but also references for studies and applications in relevant fields.
