Nature of the large-scale structures observed in the Tangent Cylinder at high criticality

Determine whether the large-scale flow structures observed within the Tangent Cylinder in the high-criticality, rotation-influenced regime of the LEE2 experiments correspond to the Large Scale Vortices identified in numerical simulations of rapidly rotating Rayleigh–Bénard convection, thereby clarifying the nature of these structures in geostrophic turbulence conditions.

Background

In LEE2 experiments, at supercriticalities R ≳ 37 the flow exhibits intense small-scale turbulence and a small number of large vorticity patches across horizontal planes, consistent with strongly rotationally constrained conditions (local Rossby number R_l ≲ 0.2). These structures resemble large-scale vortices (LSV) reported in numerical studies of geostrophic rotating convection, but the authors lack direct diagnostics (e.g., pressure-gradient balances) to confirm geostrophic balance.

The paper notes that transitions to turbulent regimes and emergence of large structures occur at lower criticalities in the Tangent Cylinder than in classical rotating Rayleigh–Bénard configurations, likely due to baroclinically driven inertia near the TC boundary. However, the precise identification of these observed structures remains unresolved.