A Personal Perspective on Wayne Schubert’s Contributions to Our Knowledge and Understanding of Cloud-Topped Boundary Layers

Wayne Schubert’s early insightful work on the modeling of cloud-topped boundary layers led the way to major advancements in our understanding and modeling of these cloud structures in the climate system. His first work on these clouds involved the application of a simple mixed layer model to a cloud-topped boundary layer first proposed by Doug Lilly in 1968. He subsequently extended this modeling effort to investigate how cloud-topped boundary layers evolved along low-level trajectories extending equatorward around the subtropical anticyclones. Wayne was one of the first scientists to recognize the climatic importance of the extensive boundary layer cloud systems that extend off the west coast of continents. Further his work underscored the importance of understanding the mechanisms that control the transition of solid cloud decks to more broken cloud fields. His early modeling work opened whole new areas of research that have expanded over the years and remain as critical elements of research on boundary layer cloud processes important to the climate system. For example, Wayne’s work stimulated extensive research on cloud-top entrainment in stratocumulus clouds. Further, his initial work provided the motivation for future studies of the transition of solid stratocumulus clouds to broken clouds. Although Wayne’s contributions to the field of cloudy boundary layers through his early publications were substantial, his contributions to this field through his mentoring of graduate students cannot be overstated. In addition to being a great role model, his enthusiasm for the science was contagious. He helped students develop critical thinking skills, taught them how to breathe life into those equations that he cherished so much, and was extremely generous with his time and visionary ideas. I personally am indebted to Wayne for the indelible mark he left on my career. In addition to Wayne’s guidance on the modeling aspects of my M.S. and Ph.D. work, Wayne provided me with an opportunity to experience marine stratocumulus clouds first-hand during (five) flights on the NCAR Electra in 1976 during an NSF project that Wayne and Doug Lilly had put together for the first-ever study of stratocumulus clouds off the coast of California. It was during one of these flights—the drizzle on the windshield flight--when I directly observed the important role that cloud physics played in boundary layer clouds. That single event had a great impact on my own career. Further, before and during the California stratus project Wayne had expressed how great it would be if we could use an aircraft to follow the evolution of air masses as they moved equatorward in the trades--the San Francisco to Hawaii dream mission. The seed he planted then would reach fruition forty years later when we were able to successfully use the NSF/NCAR GV on flights from Sacramento to Hawaii and back in support of the NSF Cloud System Evolution in the Trades (CSET) project in 2015. We need to credit Wayne’s great vision of years ago for the inspiration that led to the development and the success of CSET.

Without a doubt Wayne must be considered one of the founding fathers of the extensive research that has been done and continues to be done on cloudy boundary layers during the last half of the century. It is my pleasure and honor to pay tribute to Wayne for his outstanding contributions to our knowledge and understanding of cloud-topped boundary layers and their role in the climate system.