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江淮地区积层混合云融化层附近微物理特征及粒子谱演变研究

Study on Microphysical Characteristics and Particle Spectrμm Evolution near Melting Layer in Stratiform Clouds with Embedded Convection over the Jianghuai Region

  • 摘要: 积层混合云是我国重要降水系统,其融化层附近微物理过程直接影响降水形成与演变,是云物理和人工影响天气研究的关键环节。为揭示融化层附近云微物理特征及影响机制,本文利用机载云粒子原位观测数据,结合地基雷达资料,对2025年3月14日江淮地区积层混合云的融化层附近微物理特征开展系统分析。结果表明:本次探测冰晶主要呈现针柱状、板状、柱帽状及不规则状四种形态,-1~0oC区间内单个冰晶与聚合体共存,且冰晶边缘模糊,证实凝华、聚合及淞附三种增长过程同步发生;0~3oC融化层内冰晶逐步融化,3oC时仍存在未完全融化的固态粒子,说明该云系融化层垂直厚度较大。融化层附近冰晶形态存在显著空间差异,云系边缘以小粒径单个冰晶为主,辐枝状冰晶稀少,淞附与聚合过程较弱;而强回波区伴随过冷水含量和云顶高度提升,淞附与聚合过程增强,大粒径不规则冰晶及聚合体增多,降水粒子谱拓宽。本次观测降水粒子谱分布受温度、相对湿度及云系位置共同调控,相近温度条件下,强回波区高相对湿度环境大粒径(>700μm)和小粒径(<200μm)粒子数浓度显著高于云边缘弱回波区,200~700μm粒径段粒子由于融化速度较快,出现数浓度低谷;低相对湿度环境会抑制固态粒子融化,使200~700μm粒径段粒子数浓度无明显低谷。MP拟合显示,0oC层附近谱分布斜率λ稳定在10-3~10-2μm-1,小粒径粒子占比稳定。本研究结果可为积层混合云降水机制研究及人工增雨作业提供数据支撑及理论参考。

     

    Abstract: Stratiform clouds with embedded convections are important precipitation systems in China. The microphysical processes in their melting layer directly affect the formation and evolution of precipitation, and are key links in the research of artificial weather modification and cloud physics. To reveal the microphysical characteristics and influencing mechanisms near the melting layer, this study systematically analyzed the melting layer of a Stratiform clouds with embedded convection precipitation system that occurred in the Jianghuai region on March 14, 2025, using in-situ airborne cloud particle observation data combined with ground-based radar data. The results show that the ice crystals during the observation mainly presented four morphologies: needle-columnar, plate-like, column-cap, and irregular. Single ice crystals and aggregates coexisted in the temperature range of -1~0°C, and the edges of ice crystals were blurred, confirming that the three growth processes of sublimation, aggregation, and riming occurred simultaneously. In the melting layer of 0~3°C, ice crystals gradually melted, and some solid particles still did not melt completely at 3°C, indicating that the melting layer of the cloud system had a large vertical thickness.There were significant spatial differences in ice crystal morphologies within the melting layer. The edge of the cloud system was dominated by small-sized single ice crystals, with rare dendritic ice crystals and weak riming and aggregation processes. In the strong echo area of the cloud, with the increase of supercooled water content and cloud top height, the riming and aggregation processes were enhanced, accompanied by an increase in large-sized irregular ice crystals and aggregates, and the precipitation particle spectrum was broadened. The distribution of precipitation particle spectrum was jointly regulated by temperature, humidity, and cloud position in this case. Under similar temperature conditions,the number concentrations of large particles (>700 μm) and small particles (<200 μm) within high-humidity zones of strong radar echoes were remarkably higher than those in weak echo regions at cloud edges. Particles ranging from 200 μm to 700 μm exhibited a valley in number concentration due to their rapid melting rate. Low-humidity conditions suppressed the melting of solid hydrometeors, eliminating the obvious valley in number concentration for particles of 200–700 μm. MP fitting results showed that the spectral distribution slope λ near the 0°C layer was stable at 10?3~10?2 μm?1, indicating that the proportion of small-sized particles remained stable. The results of this study can provide a theoretical reference for the research on the precipitation mechanism of Stratiform clouds with embedded convections and artificial precipitation enhancement operations.

     

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