Data from the Winter Monsoon Experiment (WMONEX) are used to study cloud clusters that occurred over the South China Sea on 10 December 1978. These clusters underwent life cycles in which they began as groups of intense convective cells and then developed into mesoscale systems consisting partly of convective cells and partly of stratiform precipitation. In the cellular regions of clusters, ice particle concentrations (at the 8 km, or −17°C, level) were found to be of the order of hundreds per liter, local convective updrafts of 4–17 m s−1 were observed, and the dominant ice-particle growth mechanism appeared to be riming. In the stratiform regions of clusters, the ice particles appeared to grow by vapor deposition and aggregation and weaker but more widespread mesoscale updraft motion was indicated at mid to upper levels by the observed ice-crystal structures, while unsaturated mesoscale downdraft motion was indicated at mid to lower levels by sounding data. The ice-particle concentrations at 8 ... Abstract Data from the Winter Monsoon Experiment (WMONEX) are used to study cloud clusters that occurred over the South China Sea on 10 December 1978. These clusters underwent life cycles in which they began as groups of intense convective cells and then developed into mesoscale systems consisting partly of convective cells and partly of stratiform precipitation. In the cellular regions of clusters, ice particle concentrations (at the 8 km, or −17°C, level) were found to be of the order of hundreds per liter, local convective updrafts of 4–17 m s−1 were observed, and the dominant ice-particle growth mechanism appeared to be riming. In the stratiform regions of clusters, the ice particles appeared to grow by vapor deposition and aggregation and weaker but more widespread mesoscale updraft motion was indicated at mid to upper levels by the observed ice-crystal structures, while unsaturated mesoscale downdraft motion was indicated at mid to lower levels by sounding data. The ice-particle concentrations at 8 ...