Evolution pattern of marine stratocumulus clouds inferred from satellite snapshot measurements

Microphysical characteristics of stratocumulus clouds and their associated warm-rain processes have been heavily investigated by using satellite observations, particularly from cloud radar and lidar instruments aboard low-orbiting satellites. Owing to the discrete-snapshot nature of such measurements, numerous statistical relationships among microphysical properties were established, yet the processes of stratocumulus evolution cannot be reasonably delineated, with the temporal evolution of cloud microphysics remaining unclear. Based on cloud geometric thickness and cloud top height derived from the Cloud Profiling Radar (CPR) aboard CloudSat, this study proposed a method to classify pixel-level samples of stratocumulus clouds into five distinct groups, each corresponding to a specific stage in the cloud lifecycle. Given these five stages as components, an evolution pattern of stratocumulus clouds with respect to precipitation onset was constructed. It was found that there exist three evolution paths from formation to dissipation. Precipitation is nearly absent in two paths, which contain only two or three component stages and are featured as modest temporal variation of geometric thickness and microphysical properties. The other path contains all the five stages and produces considerable precipitation at its mature phase that gets the largest cloud thickness. In this path, the vertical structure of cloud droplet effective radius does not vary in phase with that of cloud droplet number concentration. The vertical structure of liquid water content generally follows that of cloud droplet effective radius. These two parameters both turn to increase monotonically downward during dissipation, where stratocumulus clouds eventually become stable as a non-precipitation thin form.