Nonlinear Processes in Oceanic and Atmospheric Flows


Atmospheric complexity or scale by scale simplicity?

Author: Shaun Lovejoy, McGill University.

Names and affiliation of other authors:

Oral or poster: Oral presentation

Downloadable talk file:

Atmospheric complexity or scale by scale simplicity?

(Cantabrianew.5.7.8.pdf, 23524254 bytes)

In 1922, Lewis Fry Richardson published the now celebrated book “Weather forecasting by numerical process” in which he daringly proposed that the weather could be forecast by brute force numerical integration of coupled nonlinear partial differential equations. But the father of numerical weather prediction was Janus-faced: his book contains a famous passage in which he proposed that the complex nonlinear atmospheric dynamics cascaded scale after scale from planetary down to small viscous scales: he is also the grandfather of modern cascade models.
The idea of scale by scale simplicity embodied in cascades is in tune with the history of science that shows that once the fundamentals are correctly grasped, that messy complexity generally gives way to simplicity and that simplicity points the way to the future. But are cascades correct?
Over the last five years, profiting from a “golden age” of atmospheric data and models of unprecedented quality and quantity, my colleagues and I have used state of the art satellite, lidar and “drop sonde” data to decisively show that over the entire range of meteorologically significant scales that the atmosphere accurately follows the predictions of cascade models.
So which Richardson is right? The father of numerical weather prediction or the grandfather of cascades? The answer may be both. This is possible because cascade models are specifically designed as phenomenological models of the equations.

*Satellite images from NASA and ESA

Nonlinear Processes in Oceanic and Atmospheric Flows. July 2-4, 2008. Castro Urdiales, Cantabria, Spain.