Clouds without fluid mechanics
Turbulent cascades that are anisotropic and multiplicative promise a coarse-grained description of Earth’s atmosphere, offering a simplification that is analogous to coarse-graining a box of particles into a continuous fluid medium. However, cascade descriptions are not yet as complete as fluid descriptions. Cascade simulations are typically homogeneous, univariate, and dimensionless. These limitations might be simple to overcome but nonetheless limit the appeal of cascades to a broader atmospheric science audience. Here, I will describe a cascade-based model, currently in development, of a convective cloud field, with the end goal being parity with hydrodynamic “large-eddy” simulations that are ubiquitous across atmospheric sciences. I will argue that such an application reveals ambiguities and limitations of cascade theory, but that these obstacles are tractable. Ultimately, cascades can and should replace fluid mechanics for simulating Earth’s atmosphere.
Thomas studies the statistical structure of Earth’s atmosphere. His Ph.D. work at the University of Utah challenges the logic behind long-standing attempts to carve up the atmosphere into discrete phenomena, from hurricanes and thunderstorms to individual clouds and wind gusts. Thomas is going to start a post-doc at the Santa Fe Institute aiming to develop scale invariance into a framework that is not only descriptive but can also be used for simulation and prediction of Earth’s atmosphere. Thomas believes that an emergent theory of scale invariant cascades could one day replace fluids as the core of our understanding of Earth’s atmosphere.