Microphysical structure and vertical evolution of continental cumulus clouds from analysis of aircraft measurements in Northern China

Microphysical characteristics of continental cumulus in relatively remote area of Northern China were studied using King Air aircraft that equipping with several cloud probes in summer of 2020. Penetrating of cumuli was achieved at several altitudes. Aircraft based KPR cloud radar showed the depth of cumulus was over 4000 m and the cloud base was near 2000 m above sea level. Cloud droplet number concentration was 400-800 cm(-3) at 3700-4300 m and decreased to 200 cm(-3) at the cloud top. Cloud droplet effective diameter increased linearly with height (3.33 mu m km(-1)) from 12 mu m (3700 m) to 18 mu m (5500 m), as the result of droplet growth by condensation or accretion, during the vertical evolution of cloud from initial generation to mature stage. Cloud droplet size spectra presented a single mode at all altitudes and the broadening of spectra with increasing altitude was apparent. LWC adiabatic ratios of < 0.3 for all altitudes indicated the strong entrainment mixing from dry air, since most of the clouds were penetrated near cloud margins. At 4300 m, drizzle drop concentration reached 17 L-1 (diameter of 60 mu m) and high concentration of ice (175 L-1, diameter gathered at 150 mu m and over 1000 mu m) containing primarily graupels was related to the secondary ice process during riming (Hallett-Mossop). Supercooled drizzle drops (60, 100 and 150 mu m in diameter) and ice particles (100-400 mu m in diameter) both had concentrations of several counts per liter at 5500 m. At the convective cloud top (6200 m), high concentrations of drizzle drops and ice particles (mainly graupels) revealed their large growth rates as atmospheric condition was more fit for the redistribution and collision/coalescence of cloud particles. To better learn the large differences of cloud properties and related microphysics for distinct levels of well-developed continental cumulus, more aircraft measurements, particularly across the cloud cores, are needed.

Automated summary

Microphysical characteristics of continental cumulus in a relatively remote area of Northern China were studied using the King Air aircraft equipped with cloud probes. The research found that cloud droplet concentration and effective diameter varied with altitude, and the cloud droplet size spectra broadened with increasing altitude. High concentrations of drizzle drops and ice particles were observed near the cloud top, indicating active redistribution and collision/coalescence processes of cloud particles. Further aircraft measurements, particularly across the cloud cores, are needed to better understand the cloud properties and microphysics of well-developed continental cumulus at different stages.