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Jonathan L. Vigh and Wayne H. Schubert

/∂ z vanish at the bottom and top isobaric surfaces z = 0, z = z T ; and that rϕ t → 0 as r → ∞. We shall refer to the right-hand side of (2.15) as the “tropical cyclogenesis function” because it gives the interior forcing function associated with nonzero ϕ t . Because of the rather complicated mathematical form given in the right-hand side of (2.15) , physical interpretation is difficult. However, using potential vorticity concepts, the tropical cyclogenesis function can be

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Chanh Q. Kieu and Da-Lin Zhang

( Emanuel 1987 ) as a route to hurricanes. The bottom-up and top-down hypotheses have been proposed as two of the possible processes leading to TCG from midlevel MCVs that often develop in the stratiform region of mesoscale convective systems (MCSs; Zhang and Fritsch 1987 ; Bartels and Maddox 1991 ). Specifically, Zhang and Bao (1996a , b) find that an MCV provides the necessary quasi-balanced forcing for the initiation and organization of (parameterized) deep convection and for the initial

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Joël Arnault and Frank Roux

when they leave the West African coast (“anticyclonic flow in the upper levels and surrounding the positive vorticity center, deep rising motion, weak and small cold core, a moist environment;” Aviles 2004 , p. 140) and, to lesser extent, on a favorable environment in the Atlantic basin (e.g., Gray 1968 ). Based on 15-yr ECMWF reanalyses, Kiladis et al. (2006) evaluated the adiabatic forcing of vertical motion with the divergence of Q vectors ( Hoskins et al. 1978 ). They found “strong

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R. A. Hansell, S. C. Tsay, Q. Ji, N. C. Hsu, M. J. Jeong, S. H. Wang, J. S. Reid, K. N. Liou, and S. C. Ou

the field. In addition, the limited experimental data on dust optical properties at infrared wavelengths and the large uncertainties in the spatially and temporally dependent particle properties—size, shape, and composition ( Sokolik and Toon 1999 )—have indeed made it a difficult challenge to constrain the LW impact. The term “aerosol radiative forcing” is now commonly used for gauging changes in the radiative fluxes due to anthropogenic aerosols since the beginning of the industrial era (∼1750

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Zhuo Wang, M. T. Montgomery, and T. J. Dunkerton

diabatic vortex merger and low-level convergence. This process occurs alongside the more familiar adiabatic merger of vortical remnants of MCSs in a prevailing cyclonic flow. From a broad scale perspective, the VHTs act collectively as a persistent thermodynamic heat forcing for the transverse circulation in the developing quasi-circular protovortex. This “Eliassen” forcing of the transverse circulation generates low-level convergence on the system scale, which enhances the preexisting cyclonic

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Wallace Hogsett and Da-Lin Zhang

dilution of TPE due to density changes. For the purposes of this study, we will consider TPE to be simply the intermediary between LE and KE, both of which will be the focus of the present study. The KE equation can be obtained by taking the dot product of the MM5 horizontal momentum equation: where KE changes because of horizontal cross-isobaric flow when work is done by air parcels against the horizontal pressure force (KGEN), friction including the boundary layer processes and vertical and

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Zhuo Wang, M. T. Montgomery, and T. J. Dunkerton

I . The control run has a four-grid nested domain configuration with horizontal grid spacing 81, 27, 9, and 3 km, respectively, initialized at 0000 UTC 29 August 2007, about 3 days prior to genesis. The initial conditions and lateral boundary forcing in the control run were derived from the ECMWF 6-hourly analyses with T106 resolution. The Kain–Fritsch scheme was used to represent cumulus convection in the two outer grids; in the two inner grids (9-km and 3-km resolution), cumulus convection was

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Edward K. Vizy and Kerry H. Cook

) suggest the need for an external influence acting upon the developing disturbance to promote genesis. Frank (1988) and Bracken and Bosart (2000) proposed that tropical cyclone development consists of two phases, genesis and intensification, each of which is dominated by different physical processes. In the genesis phase the mesoscale vortex forms rapidly within a region of loosely organized tropical convection, and external forcing may be required to produce deep convection ( Briegel and Frank

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Scott A. Braun, Michael T. Montgomery, Kevin J. Mallen, and Paul D. Reasor

Peninsula to shortly after landfall as a tropical storm. Two of the missions involved coordinated flights with the ER-2 and one P-3 aircraft, with the remainder being single aircraft missions. In addition to the flights associated with the TCSP experiment, an Air Force reconnaissance flight occurred during 0849–1736 UTC 24 July, thus providing greater continuity of measurements during the life cycle of Gert. Table 1 provides a summary of the different flights. See Halverson et al. (2007) for a

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Robert Rogers

environmental, vortex, and convective scales. Kaplan and DeMaria (2003) , using the Statistical Hurricane Intensity Prediction Scheme (SHIPS) database, identified several environmental conditions associated with RI: warm sea surface temperatures and deep oceanic mixed layers, high lower-tropospheric relative humidity, low vertical shear, weak upper-level forcing from troughs or cold lows, and upper-level easterly flow. These findings are consistent with what has been found by previous observational and

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