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Andrew J. Heymsfield, Aaron Bansemer, Gerald Heymsfield, and Alexandre O. Fierro

1. Introduction Cirrus clouds at a given time cover about 20% of tropical latitudes and contribute significantly to regional and global radiation budgets ( Rossow and Schiffer 1999 ). Optically thick tropical cirrus are produced primarily through deep convection and generate as much as 25% of the earth’s net cloud radiative forcing ( Hartmann et al. 1992 ). The primary impact of thin versus thick cirrus is on the shortwave energy budget, and the albedo of these ice clouds depends on their

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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

cumulus convection in the two outer grids; in the two inner grids (9-km and 3-km resolution), cumulus convection was calculated explicitly at the grid scale. Other physics parameterizations used include WRF single-moment, six-class microphysics ( Hong and Lim 2006 ) and the Yonsei University (YSU) planetary boundary layer scheme ( Noh et al. 2003 ), Rapid Radiative Transfer Model (RRTM) longwave radiation scheme ( Mlawer et al. 1997 ), and the Dudhia (1989) shortwave radiation scheme. Sensitivity

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Joël Arnault and Frank Roux

), the thermodynamic equation of Bannon (2002) becomes In (25) , the tendency of H m C is equal to the sum of flux divergence BH C and source terms: the pressure tendency G p C ; the total pressure work (CP C + CPV C ); the term associated with changes of water phase ; the heating rate due to other diabatic processes (e.g., radiative heating and turbulent dissipation) ; the opposite of the total heating rate of hydrometeors (this term appears because we consider the variation of moist

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Zhaoxia Pu, Xuanli Li, and Juanzhen Sun

and atmospheric research needs. The WRF model features multiple dynamic cores. This study employs the Advanced Research WRF model (ARW-WRF). The ARW-WRF is based on an Eulerian solver for the fully compressible nonhydrostatic equations, cast in flux conservation form and using a mass (hydrostatic pressure) vertical coordinate. The solver uses a third-order Runge–Kutta time integration scheme coupled with a split-explicit second-order time integration scheme for the acoustic and gravity wave modes

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Syed Ismail, Richard A. Ferrare, Edward V. Browell, Gao Chen, Bruce Anderson, Susan A. Kooi, Anthony Notari, Carolyn F. Butler, Sharon Burton, Marta Fenn, Jason P. Dunion, Gerry Heymsfield, T. N. Krishnamurti, and Mrinal K. Biswas

that deficiencies in the modeling of moisture and diabatic processes are due in part to the lack of knowledge of the tropical humidity fields. Model forecasts are very sensitive to the surface layer moisture. Krishnamurti and Oosterhof (1989) showed that models that incorporated an explicitly resolved surface layer were able to more accurately compute the strong moisture flux between the ocean and atmosphere, resulting in more accurate prediction of the formation of hurricanes. Results from the

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

-theory surface-layer scheme ( Zhang and Anthes 1982 ; Skamarock et al. 2005 ), the Noah land surface scheme ( Chen and Dudhia 2001 ), the Kain–Fritsch cumulus scheme ( Kain and Fritsch 1990 , 1993 ; Skamarock et al. 2005 ) on the 54- and 18-km grids only and calculated every time step, and the WRF single-moment six-class cloud microphysics ( Hong et al. 2004 ) on all grids. Radiative processes are calculated every 5 min on the 54- and 18-km grids and 2 min on the 6- and 2-km grids using the Rapid

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Chanh Q. Kieu and Da-Lin Zhang

global models in predicting TC tracks indicate that the large-scale circulation is the key parameter in determining where TCG may occur. It is well known that the large-scale conditions conducive for TCG over different ocean basins include weak vertical wind shear ( Gray 1968 ; McBride and Zehr 1981 ; DeMaria 1996 ), warm sea surface temperature (SST) and deep moist layers ( Emanuel 2000 ), well-organized angular momentum fluxes ( Challa and Pfeffer 1990 ), easterly waves ( Molinari et al. 2000

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Edward K. Vizy and Kerry H. Cook

( Emanuel 1989 ; Powell 1990 ; Dunion and Velden 2004 ). 3. Model description and experimental design The model used to conduct the simulations for this study is the NCAR–NOAA WRF model ( Skamarock et al. 2005 ). It is a fully compressible, nonhydrostatic model whose governing equations are cast in flux form and solved using a time-split integration scheme that accounts for both low and high frequency modes. The vertical coordinate system is terrain following. Here, we use 31 vertical levels, with the

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