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( 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
( 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
hypothesis after many subsequent years of thunderstorm investigation, Wilson (1920 , p. 112) gave equal attention to thunderclouds and electrified shower clouds as “batteries” for the global circuit. In his words: “A thundercloud or shower-cloud is the seat of the electromotive force which must cause a current to flow through the cloud between the earth’s surface and the upper atmosphere … In shower-clouds in which the potentials fall short of what is required to produce lightning discharges, there is
hypothesis after many subsequent years of thunderstorm investigation, Wilson (1920 , p. 112) gave equal attention to thunderclouds and electrified shower clouds as “batteries” for the global circuit. In his words: “A thundercloud or shower-cloud is the seat of the electromotive force which must cause a current to flow through the cloud between the earth’s surface and the upper atmosphere … In shower-clouds in which the potentials fall short of what is required to produce lightning discharges, there is
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
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
1. Introduction This is the second of a two-part study examining the numerically simulated formation of Atlantic Hurricane Felix (2007) in a cloud-representing framework. In Part I of this study ( Wang et al. 2010 , hereafter Part I ) the simulation commenced during the wave stage of the precursor African easterly wave disturbance. Analysis of the real-case simulation pointed to a bottom-up development process within the parent wave’s cyclonic “cat’s eye” recirculation flow (or the wave
1. Introduction This is the second of a two-part study examining the numerically simulated formation of Atlantic Hurricane Felix (2007) in a cloud-representing framework. In Part I of this study ( Wang et al. 2010 , hereafter Part I ) the simulation commenced during the wave stage of the precursor African easterly wave disturbance. Analysis of the real-case simulation pointed to a bottom-up development process within the parent wave’s cyclonic “cat’s eye” recirculation flow (or the wave
. Bull. Amer. Meteor. Soc. , 86 , 1795 – 1809 . Brindley , H. E. , 2007 : Estimating the top-of-atmosphere longwave radiative forcing due to Saharan dust from satellite observations over a West African surface site. Atmos. Sci. Lett. , 8 , 74 – 79 . Campbell , J. R. , D. L. Hlavka , E. J. Welton , C. J. Flynn , D. D. Turner , J. D. Spinhirne , V. S. Scott , and I. H. Hwang , 2002 : Full-time, eye-safe cloud and aerosol lidar observation at Atmospheric Radiation
. Bull. Amer. Meteor. Soc. , 86 , 1795 – 1809 . Brindley , H. E. , 2007 : Estimating the top-of-atmosphere longwave radiative forcing due to Saharan dust from satellite observations over a West African surface site. Atmos. Sci. Lett. , 8 , 74 – 79 . Campbell , J. R. , D. L. Hlavka , E. J. Welton , C. J. Flynn , D. D. Turner , J. D. Spinhirne , V. S. Scott , and I. H. Hwang , 2002 : Full-time, eye-safe cloud and aerosol lidar observation at Atmospheric Radiation
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
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
subsidence are found inside the radius of maximum winds. At low levels, air flowing in toward the radius of maximum wind meets air flowing outwards from the eye, forcing a strong updraft at or near the radius of maximum wind. Thus, in the overwhelming majority of cases, the radius of maximum wind occurs within the eyewall cloud. 4 In fact, on average, the radius of maximum wind was located 8–10 km outward from the inner edge of the eyewall (as observed by aircraft radar). Jorgensen (1984) made
subsidence are found inside the radius of maximum winds. At low levels, air flowing in toward the radius of maximum wind meets air flowing outwards from the eye, forcing a strong updraft at or near the radius of maximum wind. Thus, in the overwhelming majority of cases, the radius of maximum wind occurs within the eyewall cloud. 4 In fact, on average, the radius of maximum wind was located 8–10 km outward from the inner edge of the eyewall (as observed by aircraft radar). Jorgensen (1984) made
1. Introduction Tropical cyclones (TCs) devastate life and property by concentrating large amounts of kinetic energy (KE) within a small radius in the inner-core regions. Most of the KE is generated through a continuous series of energy conversions, with the latent energy (LE) as the fundamental source, which is obtained primarily through upward fluxes of latent heat from the underlying warm ocean and released in convective clouds in the eyewall. Some of the released LE is used to increase KE
1. Introduction Tropical cyclones (TCs) devastate life and property by concentrating large amounts of kinetic energy (KE) within a small radius in the inner-core regions. Most of the KE is generated through a continuous series of energy conversions, with the latent energy (LE) as the fundamental source, which is obtained primarily through upward fluxes of latent heat from the underlying warm ocean and released in convective clouds in the eyewall. Some of the released LE is used to increase KE
a HT that they hypothesized played a large role in the development of the warm core. In general, the PV anomalies associated with an asymmetric distribution of HTs (or VHTs) are axisymmetrized into the parent circulation via vortex Rossby wave dynamics ( Montgomery and Kallenbach 1997 ; Montgomery and Enagonio 1998 ). In their cyclogenesis experiments, Montgomery and Enagonio (1998) showed how convectively induced eddy heat and momentum fluxes (a by-product of vortex Rossby waves) can force
a HT that they hypothesized played a large role in the development of the warm core. In general, the PV anomalies associated with an asymmetric distribution of HTs (or VHTs) are axisymmetrized into the parent circulation via vortex Rossby wave dynamics ( Montgomery and Kallenbach 1997 ; Montgomery and Enagonio 1998 ). In their cyclogenesis experiments, Montgomery and Enagonio (1998) showed how convectively induced eddy heat and momentum fluxes (a by-product of vortex Rossby waves) can force
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
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
