Walter Robinson, Professor

As global models evolve from climate models into Earth-system models, it is generally assumed that the basic dynamics of Earth’s fluids are simulated well. There remain, however, persistent biases in how models represent the dynamics of Earth’s atmosphere, even on the largest and putatively well-resolved scales. Thus, the development of better Earth-system models requires continued attention to how they represent the basic dynamics of the atmosphere and the ocean, at the same time that novel new processes are introduced. The best possible treatment of a biogeochemical process will likely fail if driven by erroneous dynamics.

No process in an Earth-system model is less glamorous than the extratropical zonal winds and their maintenance, yet significant model biases in zonal winds remain. These can be traced to uncertainties in gravity-wave drag, a which is poorly observed and understood but which plays a crucial role in the momentum budget of the atmosphere. Model zonal winds are sensitive to small errors in gravity-wave drag, for reasons that have only recently been understood and that will be elucidated in this seminar.

Failing to offer an immediate solution to this problem, a less hubristic approach to Earth-system modeling than that currently in vogue will be advocated.