In the discussions of cloud microphysical processes, we have implicitly assumed that the dynamical and thermodynamic environments remain unchanged. In reality, cloud microphysical processes are closely coupled with dynamics and thermodynamics, such that changes in cloud microphysics will lead to changes in cloud dynamics and thermodynamics, and vice versa. For example, a phase change of water substance will cause the release or consumption of latent heat, which will heat or cool the surrounding air and eventually lead to air motion. The formation of large hydrometeors such as raindrops or hail increases the downward drag of the air parcel they are in and thus may cause the air to descend. The ascent or descent of air causes cooling or heating due to adiabatic expansion or compression, and may lead to the formation or dissipation of hydrometeors.

To really take these interactions into account, we need to develop a cloud model that includes the coupled dynamical, thermodynamic, and microphysical processes. We will discuss the cloud models in the next chapter, but it is useful to review some key dynamical processes of cloud development in a simplified setting so as to understand the fundamental processes involved. This is the subject of this chapter.