Inverse Transfer and Coherence in Rotating Stratified Flow with Clouds and Phase Transitions

Inverse energy transfer to large-scale coherent structures in idealized models of geophysical flows has been of interest for over four decades.

Extensive knowledge exists regarding inverse transfer in rotating and stratified dry dynamics, characterized by the Rossby number and a single dry Froude number.

The current study includes effects of water and phase changes, with dynamics characterized by the Rossby number and two Froude numbers for unsaturated and saturated environments.

Using numerical computations with random forcing, inverse energy transfer is examined for a model with a Boussinesq dynamical core, incorporating water vapor and liquid water in the limit of asymptotically-fast cloud microphysics.

Besides kinetic energy, total energy includes buoyant potential energies from each phase, and latent moist energy responsible for potential energy transfer at phase boundaries.

The rotation and stratification terms are large and comparable, such that the dry version of the evolution equations is dominated by inverse transfer of pseudo potential vorticity(PV).

For fixed Rossby and dry (unsaturated) Froude numbers, compared to dry dynamics, there is a reduction in energy transfer rate, associated with the larger Froude number of saturated regions.

The upscale transfer to moist PV is influenced by nonlinear waves at lowest order resulting from nonlinear buoyancy near phase interfaces.

These nonlinear waves lead to coherent updrafts and downdrafts roughly aligned with fuzzy, large-scale phase boundaries identified by the time average of a cloud indicator function.

Statistical relationships between phase boundaries, updrafts/downdrafts and moist PV are explored in flow regions dominated by moist PV-vortices.