Stratocumulus Mixed Layer Modeling and Entrainment—The View After 38 Years of Standing on Doug Lilly's Shoulders

38 years later, Doug Lilly's 1968 paper pioneering the use of mixed layer modeling to understand subtropical stratocumulus-topped boundary layers still is required reading for new students learning about this field. In the mathematical simplicity of mixed layer modeling are hidden important subtleties that are still poorly understood. Chief among these is entrainment closure, followed by decoupling and drizzle feedbacks.

I will review what we have learned about the strengths and limitations of stratocumulus mixed layer modeling since 1968 by playing it off against field data and large-eddy simulations. I will also give a contemporary perspective on entrainment closure, including a critical analysis of Lilly's original entrainment closures and a discussion of work on the subject he did 30 years later. I will close by mentioning some current applications of mixed layer models to feedbacks between stratocumulus and greenhouse and aerosol-induced climate perturbations.