Moist multi-scale models for the hurricane embryo

• Published in: Journal of fluid mechanics Vol. 657; pp. 478 - 501
• Main Authors: MAJDA, ANDREW J., XING, YULONG, MOHAMMADIAN, MAJID
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 25.08.2010
• Subjects: ATMOSPHERIC CIRCULATION; Balances (scales); Cloud physics; CLOUDS; Computational fluid dynamics; Cyclogenesis; Earth, ocean, space; Embryos; ENVIRONMENTAL SCIENCES; Exact sciences and technology; External geophysics; Fluid flow; Fluid mechanics; Geophysics. Techniques, methods, instrumentation and models; Gravity waves; HURRICANES; HYDRODYNAMICS; Mathematical analysis; MATHEMATICAL MODELS; METEOROLOGY; MOISTURE; Nonlinear dynamics; Nonlinear systems; Scale models; Storms, hurricanes, tornadoes, thunderstorms; THERMODYNAMICS; hurricanes; Severe weather; Tropical cyclone; Multiscale method; digital simulation; Dynamic model; asymptotic approximation; Modeling; Formation mechanism; Preconditioning; Cyclogenesis
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/S0022112010001515

Determining the finite-amplitude preconditioned states in the hurricane embryo, which lead to tropical cyclogenesis, is a central issue in contemporary meteorology. In the embryo there is competition between different preconditioning mechanisms involving hydrodynamics and moist thermodynamics, which can lead to cyclogenesis. Here systematic asymptotic methods from applied mathematics are utilized to develop new simplified moist multi-scale models starting from the moist anelastic equations. Three interesting multi-scale models emerge in the analysis. The balanced mesoscale vortex (BMV) dynamics and the microscale balanced hot tower (BHT) dynamics involve simplified balanced equations without gravity waves for vertical vorticity amplification due to moist heat sources and incorporate nonlinear advective fluxes across scales. The BMV model is the central one for tropical cyclogenesis in the embryo. The moist mesoscale wave (MMW) dynamics involves simplified equations for mesoscale moisture fluctuations, as well as linear hydrostatic waves driven by heat sources from moisture and eddy flux divergences. A simplified cloud physics model for deep convection is introduced here and used to study moist axisymmetric plumes in the BHT model. A simple application in periodic geometry involving the effects of mesoscale vertical shear and moist microscale hot towers on vortex amplification is developed here to illustrate features of the coupled multi-scale models. These results illustrate the use of these models in isolating key mechanisms in the embryo in a simplified content.