Dynamics of mesoscale vortices generated by turbulent convection at large aspect ratios

Turbulent convection from a localized circular top surface into a rotating, homogeneous layer has been investigated in a cylindrical laboratory tank. The initial conditions for the experiments were selected so that the aspect ratio R / H ≫1 and a three‐dimensional turbulent layer penetrated with speed u ≈(0.6±0.1) ( B 0 h ) 1/3 and then spread radially in the form of a gravity front upon reaching the bottom of the tank (here B 0 is the buoyancy flux, h is the local depth, H is the total depth, and R is the radius of the source). This front later underwent a baroclinic instability generating mesoscale vortices with maximum density g ′≈(10±1) ( B 0 R ) 2/3 / H . Measurements and theoretical arguments have enabled us to scale the number of vortices N ≈(1.5±0.3) ( R 0, R ) −2/3 ( R / H ) −3/5 , their mean diameter D / R ≈8 (( R 0, R ) 2/3 , swirl velocity ν≈( B 0 R ) 1/3 , and relative voracity ƒ′/ƒ≈0.5 (here ( R 0, R ) = ( B 0 ƒ 3 R 2 ) 1/2 is a Rossby number based on R , and ƒ is the Coriolis parameter). An application of the present study to deep convective events observed in the Golfe du Lions compares favorably with the field observations.