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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

1. Introduction For over a decade, there have been many observational and theoretical efforts to determine the radiative impact of airborne mineral dust on the earth–atmosphere system (e.g., Mahowald et al. 2006 ; Haywood et al. 2003 , 2005 ; Zhang and Christopher 2003 ; Hsu et al. 2000 ; Sokolik and Toon 1996a , b ; Ackerman and Chung 1992 ). Less attention, however, has been given to the longwave (LW) contributions, mainly because the shortwave (SW) measurements are easier to make in

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Chanh Q. Kieu and Da-Lin Zhang

1. Introduction Despite considerable progress in the forecasts of tropical cyclone (TC) track and intensity during the past few decades, tropical cyclone genesis (TCG), a process by which a weak atmospheric disturbance grows into a tropical storm (TS), still remains elusive, partly because of the lack of high-resolution observations at the very early stage of TCG and partly because of the deficiencies in current TC models. In general, there are numerous tropical disturbances of different scales

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Jonathan L. Vigh and Wayne H. Schubert

the coefficients A , B , and C . However, for applications to tropical cyclones, there are several disadvantages to Eliassen’s approach: (i) the effects of top and bottom boundary conditions and the circular geometry are not included, (ii) the important spatial variability of the inertial stability coefficient C is not included, and (iii) the diabatic heating is localized in z , whereas in tropical cyclones it is rather smoothly distributed over the whole troposphere [for examples of

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Stephen R. Guimond, Gerald M. Heymsfield, and F. Joseph Turk

and effective resolution, which will be discussed in greater depth in section 2b . b. Hot towers Several decades of research have highlighted the role of horizontally small, intense cores of rapidly rising, nearly undiluted air that reach and/or penetrate the tropopause (“hot towers” or HTs) in the tropical atmosphere, including TCs ( Riehl and Malkus 1958 ; Malkus and Riehl 1960 ; Gentry et al. 1970 ; Steranka et al. 1986 ; Simpson et al. 1998 ; Heymsfield et al. 2001 ; Kelley et al. 2004

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Joël Arnault and Frank Roux

; Thompson et al. 1979 ). Several decades of observations have confirmed that a large proportion of Atlantic hurricanes evolve from AEWs (e.g., Avila and Clark 1989 ). However, few AEWs have a cyclogenetic evolution and the physical processes leading to such developments are not yet fully understood, although several hypotheses have been made. Landsea and Gray (1992) found a positive correlation between the Atlantic cyclonic activity and West Sahel rainfall variability during the summer months. This

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