Brad Ferrier Lecture: Scale-Matching Physics and Dynamics in Atmospheric Models

Leo J. Donner
  6 Sept, 2pm

Cloud microphysics, cloud macrophysics, cloud-aerosol interactions, convection, and turbulence in the planetary layer continue to pose challenges and provide opportunities for Earth system and numerical weather prediction models. Recent paleo-climate experiments show the limitations of tuning for parameterizations of these physical processes. Simulations of climates for which observations were not used in model calibration can fail. Improvements in physical realism and numerical treatments of cloud microphysics translate into better skill in numerical weather prediction.

Key to successful modeling of these processes is accurate representation of both the physical (and chemical) processes and the driving dynamics. Liquid and ice activation in clouds are controlled by vertical velocity as well as the chemical composition and sizes of aerosols. Given the significant nonlinearities involved, the scales of the dynamics (vertical velocities) must match the scales on which these physical processes occur in the atmosphere. Both resolved and parameterized vertical velocities are essential to the requisite scale matching. Parameterizations have been developed which provide sub-grid parameterizations for vertical velocities, and kilometer-scale models offer unprecedented resolution. Both offer paths toward scale-matching physics and dynamics in atmospheric models, but require substantial evaluation against observations. In recent years, field studies and inferences from satellite observations have begun to provide the needed observational constraints.