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华东地区一次积层混合云降水中融化层附近微物理特征分析

Analysis of Microphysical Characteristics near the Melting Layer in Stratiform Precipitation with Embedded Convection in East China

  • 摘要: 云中融化层的微物理特征对于云层结构和降水的形成有着至关重要的影响。本文利用中国气象局人工影响天气中心空中国王350飞机上搭载的机载Ka波段降水云雷达(Airborne Ka-Band Precipitation Cloud Radar,KPR)和云粒子原位观测仪等数据,分析了2023年9月15日华东地区一次积层混合云降水云系中融化层附近的云微物理特征。结果表明,在0℃层以上,云中粒子主要通过淞附和聚并增长,以聚合的霰粒子为主。当冰相粒子下落经过0℃后开始融化,霰粒子和大冰晶融化逐渐融化为小液滴。随着高度的降低,KPR的径向速度和谱宽逐渐增大,表明云中降水粒子相对速度变大,粒子碰并增长占主导作用,小液滴通过碰并过程增长为大液滴,形成降水。通过拟合云滴谱和降水粒子谱表明:Gamma分布能够较好的拟合云滴谱和降水粒子谱。在0℃层以上,云滴谱的斜率随高度下降而逐渐增大,降水粒子谱随高度下降而逐渐减小。但在0℃层以下,云滴谱和降水粒子谱的斜率均随高度下降呈先增大后减小的变化趋势。

     

    Abstract: The microphysical characteristics of the melting layer in clouds have a critical impact on cloud structure and precipitation formation. Utilizing the Airborne Ka-Band Precipitation Cloud Radar (KPR) and in-situ observation instrument onboard the King Air 350 aircraft of the Weather Modification Center, CMA. This study analyzed the cloud microphysical characteristics near the melting layer during stratiform precipitation with embedded convection in east China on September 15, 2023. The results show that above 0℃, the particles in the cloud mainly gather and grow through rime, and the aggregated graupel particles are the main ones. When the ice phase particles falling and melting after 0℃, graupel particles and large ice crystals melting and gradually transform into small droplets. With the decreasing of the altitude, the radial velocity and spectrum width of KPR gradually increased, indicating that the size of precipitation particles in the cloud increased, the relative velocity of particles soared, and the particles are more likely to collide and grow, and then small droplets grow into large droplets through the collision process. By fitting cloud and precipitation particle spectrums, it is showed that Gamma distribution can fit cloud and precipitation particle spectrums well. Above the 0℃ layer, the slope of cloud droplets spectrum increases with decreasing-altitude, and the precipitation particle spectrum decreases with decreasing-altitude. However, below the 0°C layer, the slopes of both spectra initially increase and then decrease with decreasing-altitude.

     

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