Donald R. Johnson: Wise Words—Great Impacts - His Lifelong Journey to Understand and Predict the General, Synoptic, and Mesoscale Circulations that Drive our Climate and Weather

In this opening paper for the Donald R. Johnson Symposium, we provide a brief historical summary of Don's lifelong effort in the research and education related to the study of the Earth's wondrous atmospheric circulation regimes. His research reaches back to the intellectual giants Max Margules, Sir Napier Shaw and Constantin Carathéodory and builds upon the insights he gained from his interactions with Sverre Petterssen, Arnt Eliassen, and Edwin Danielsen. His work includes providing the basic understanding of the 1) conversion between available potential energy and kinetic energy (Johnson and Dutton, 1967), and 2) structure and evolution of the global, synoptic and mesoscale circulation regimes.

Johnson's research 1) focuses on the basic principles involving the conservation of energy, mass, angular momentum, and entropy; 2) simplifies horizontal transport by fully capturing the horizontal adiabatic components of transport vectors while relegating the vertical component to diabatic processes (through the use of the isentropic framework); 3) ensures that the spurious non-conserving aspects of the transports are minimized; 4) provides unifying concepts to the general circulation and cyclone evolution based on the conservation of angular momentum and the fundamental importance of the horizontal gradient of the mass distribution (static stability); and 5) relates these same principles to the study of the hydrodynamic stability associated with the jet stream and mesoscale circulation patterns. The last step in this journey has been a foray into the prediction issues related to extending useful model-based predictions from days to weeks to years, based on the same isentropic coordinate approach and conserving the basic state parameters he applied to describe the global circulation regimes.

The talk is designed to set the stage for the celebration of Don's career which follows, to reflect on the ongoing advances in our understanding and ability to predict that are either directly or indirectly linked to his work. Finally, this celebration builds from his educational legacy, of which he is most proud, as illustrated by his many students who continue to try to keep up with his ongoing work and make their own impacts on this field—as he always knew we could, and would.