An explanation of actiniae cloud patterns
Ernest Agee, Purdue Univ., West Lafayette, IN
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.
Extended Abstract (1.3M)
Session 4, Marine Clouds and VOCALS II
Tuesday, 31 January 2006, 8:30 AM-9:45 AM, A309
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