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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 over 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,在融化层以上,云中粒子主要通过凇附和聚并增长,以聚合的霰粒子为主。当冰相粒子下落经过融化层后开始融化,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。在融化层以上,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。但在融化层以下,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 (ML) play a crucial role in shaping cloud structures and precipitation formation. In this study, the cloud microphysical characteristics near the ML in stratiform precipitation with embedded convection over East China on September 15, 2023, are analyzed. The data are collected using an airborne Ka-band precipitation cloud radar (KPR) and a suite of in situ observation instruments onboard a King Air 350 aircraft operated by the Weather Modification Center of the China Meteorological Administration. The results show that above the ML, cloud particles primarily grow through riming and aggregation, with aggregated graupel particles being predominant. As ice-phase particles fall through the ML, they begin to melt, and graupel particles and large ice crystals gradually transform into small liquid droplets. With decreasing altitude, both the radial velocity and spectral width observed by the KPR gradually increase, and particle growth becomes dominated by collision and coalescence. Small droplets subsequently grow into larger ones through this process, ultimately forming precipitation. Fitted particle size distributions indicate that the Gamma distribution provides a good fit to both cloud and precipitation particle spectra. Above the ML, the slopes of the cloud droplet spectra and precipitation particle spectra gradually increase and decrease, respectively, with decreasing altitude. However, below the ML, the slopes of both the cloud droplet and precipitation particle spectra first increase and then decrease with decreasing altitude.

     

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