An explanation of actiniae cloud patterns

Actiniae cloud patterns are discussed as a natural feature of thermal convection, as seen in ‎classical theoretical and laboratory experiments. The occurrence of actiniae in convective ‎marine PBLs can be viewed as a transition (or defect) in cellular geometry that is responding to ‎the appropriate atmospheric conditions of "effective" Rayleigh Number (Ra) and "effective" ‎Prandtl Number (Pr). Geometric changes in thermal convection should respond to physical ‎changes that result in the most efficient means of heat transfer (a meteorological version of the ‎Le Chatalier Principle). A regime stability diagram for atmospheric thermal convection in ‎marine PBLs is proposed, which includes actiniae. A simple laboratory convection experiment ‎has been performed in vegetable oil for conditions of Pr = 800 and Ra = 300 x Rac, which shows ‎an actinia-like structure at moderately large supercritical Rayleigh Number. The atmosphere ‎continues to be a remarkable fluid, capable of displaying instability phenomena that have ‎solutions embedded in the Navier-Stokes Equations.‎