Cloud Microphysics Across Scales for Weather and Climate

Cloud microphysics describes the evolution of condensed water in the atmosphere and is critical for weather and climate. This chapter describes the methods used for representing microphysical processes in weather and climate models, from explicit bin schemes used for small-scale simulation up to bulk treatments often used in global models. Of particular importance is how the cloud microphysical treatments are coupled to the rest of the cloud schemes in a numerical model that includes clouds. The key issues include the presentation of sub-grid inhomogeneity in humidity and dynamics. In addition, treatment of cold clouds in a “mixed phase” where liquid and ice may co-exist is important. We discuss current approaches including more comprehensive representations of ice and snow, treatment of rimed ice (graupel or hail), and coupling to unified turbulence schemes. Finally, we discuss possible paths forward for simulating cloud microphysics.