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

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.