Abstract: Based on data obtained from an airborne particle measurement system,weather radar,and Ka-band cloud radar,we analyzed the microphysical structure of mixed convective-stratiform clouds during a precipitation event caused by a low-trough cold front in Hebei province on May 22,2017.The results indicated that precipitation clouds are observed in the southwesterly flows ahead of a low trough.The mixed convective-stratiform clouds are large-scale stratiform clouds embedded with numerous convective-cloud-nuclei structures.The 0℃-layer height is about 3577-4004 m,and it decreases with the development of precipitation.The enhancement of embedded convection lifts the cloud top.The number concentration of cloud particles increases from 1.8×10⁵ to 5.0×10^-5 L^-1 due to the occurrence and enhancement of convection in clouds.Meanwhile,the supercooled water content in the clouds rises significantly from 0.05 to 0.60 g·m^-3.The supercooled water content in the upper layers of the cold clouds remains around 0.2 g·m^-3 and accounts for 60% of the total liquid in the upper and middle layers.The growth rate of ice crystals is enhanced due to the adequate supply of supercooled liquid water.The ice crystal concentrations increase explosively in the lower layers of cold clouds in the presence of weak convection and increase rapidly in the upper and middle layers of the cold clouds in the presence of strong convection.The maximum diameter of precipitation particles increases from 8000 to more than 10000 μm and the spectral distribution of maximum precipitation particles with diameter larger than 10000 μm spans from the bottom to the upper-middle layers in the clouds.

Key words: Mixed convective-stratiform clouds, Vertical detection, Cloud microphysical structure, Cloud particle spectrum