Shallow cumulus and cumulonimbus clouds are nearly ubiquitous throughout the subtropics and tropics, both over land and ocean. They are the basic building blocks from which larger cloud features develop. Tropical cyclones, for example, develop out of the growth of many clouds that were at one point relatively isolated and shallow. Mesoscale systems in the intertropical convergence zone or the Madden-Julian Oscillation are preceded by shallow convection, and shallow convection may, in some instance, precede monsoon onset. An inability to represent such small clouds in models of the atmosphere contributes to difficulty in explaining much larger events that directly impact human civiliation. However, little is known about the detailed structure of small convective clouds and how they grow into deeper precipitating cumulonimbus clouds. For example, what causes clouds to grow exactly when and where they do? Why do some clouds grow while other nearby ones do not? CaRS currently studies the thermodynamic and dynamic mechanisms responsible for cloud growth in marine and continental environments.
Only recently have targeted observations been collected to explore cumulus cloud structure. These have been enabled by the combination of remote sensing at high frequencies with direct aircraft investigation of convection and its environment. Observations that are highly resolved in space and time are needed to understand the rapid processes that lead to cloud evolution. These include observations of the boundary layer beneath clouds, the environments surrounding clouds, and air inside the clouds themselves. One such effort was the CALICO field experiment conducted in 2022.
