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

observations to characterize microphysical properties within the highly supercooled and overlying regions of tropical maritime deep convection, including cases in which low-level dust was entrained into the convective core. The focus in this paper is on the exploration of the microphysical properties and processes relevant to the −20 to −60°C temperature range of deep maritime tropical convection. Such regions cover 3% of the tropics directly, with a much larger percentage when considering the cirrostratus

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Robert Cifelli, Timothy Lang, Steven A. Rutledge, Nick Guy, Edward J. Zipser, Jon Zawislak, and Robert Holzworth

the tropical Atlantic. J. Climate , 20 , 5041 – 5060 . Gamache , J. F. , and R. A. Houze Jr. , 1983 : Water budget of a mesoscale convective system in the tropics. J. Atmos. Sci. , 40 , 1835 – 1850 . Geerts , B. , and T. Dejene , 2005 : Regional and diurnal variability of the vertical structure of precipitation systems in Africa based on spaceborne radar data. J. Climate , 18 , 893 – 916 . Gu , G. , R. F. Adler , G. J. Huffman , and S. Curtis , 2004 : African

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Jonathan Zawislak and Edward J. Zipser

Abstract

The African Monsoon Multidisciplinary Analyses (AMMA) experiment and its downstream NASA extension, NAMMA, provide an unprecedented detailed look at the vertical structure of consecutive African easterly waves. During August and September 2006, seven easterly waves passed through the NAMMA domain: two waves developed into Tropical Cyclones Debby and Helene, two waves did not develop, and three waves were questionable in their role in the development of Ernesto, Florence, and Gordon. NCEP Global Data Assimilation System (GDAS) analyses are used to describe the track of both the vorticity maxima and midlevel wave trough associated with each of the seven easterly waves. Dropsonde data from NAMMA research flights are used to describe the observed wind structure and as a tool to evaluate the accuracy of the GDAS to resolve the structure of the wave. Finally, satellite data are used to identify the relationship between convection and the organization of the wind structure. Results support a necessary distinction between the large-scale easterly wave trough and smaller-scale vorticity centers within the wave. An important wave-to-wave variability is observed: for NAMMA waves, those waves that have a characteristically high-amplitude wave trough and well-defined low-level circulations (well organized) may contain less rainfall, do not necessarily develop, and are well resolved in the analysis, whereas low-amplitude (weakly organized) NAMMA waves may have stronger vorticity centers and large persistent raining areas and may be more likely to develop, but are not well resolved in the analysis.

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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

Abstract

The Lidar Atmospheric Sensing Experiment (LASE) on board the NASA DC-8 measured high-resolution profiles of water vapor and aerosols, and cloud distributions in 14 flights over the eastern North Atlantic during the NASA African Monsoon Multidisciplinary Analyses (NAMMA) field experiment. These measurements were used to study African easterly waves (AEWs), tropical cyclones (TCs), and the Saharan air layer (SAL). These LASE measurements represent the first simultaneous water vapor and aerosol lidar measurements to study the SAL and its interactions with AEWs and TCs. Three case studies were selected for detailed analysis: (i) a stratified SAL, with fine structure and layering (unlike a well-mixed SAL), (ii) a SAL with high relative humidity (RH), and (iii) an AEW surrounded by SAL dry air intrusions. Profile measurements of aerosol scattering ratios, aerosol extinction coefficients, aerosol optical thickness, water vapor mixing ratios, RH, and temperature are presented to illustrate their characteristics in the SAL, convection, and clear air regions. LASE extinction-to-backscatter ratios for the dust layers varied from 35 ± 5 to 45 ± 5 sr, well within the range of values determined by other lidar systems. LASE aerosol extinction and water vapor profiles are validated by comparison with onboard in situ aerosol measurements and GPS dropsonde water vapor soundings, respectively. An analysis of LASE data suggests that the SAL suppresses low-altitude convection. Midlevel convection associated with the AEW and transport are likely responsible for high water vapor content observed in the southern regions of the SAL on 20 August 2008. This interaction is responsible for the transfer of about 7 × 1015 J (or 8 × 103 J m−2) latent heat energy within a day to the SAL. Initial modeling studies that used LASE water vapor profiles show sensitivity to and improvements in model forecasts of an AEW.

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Gerald M. Heymsfield, Lin Tian, Andrew J. Heymsfield, Lihua Li, and Stephen Guimond

, Black et al. (1996) used radial velocities from the NOAA WP-3D tail Doppler radar and reported supercell-like structure in Hurricane Emily (1987) with updrafts and downdrafts as strong as 24 and 19 m s −1 , respectively. They found that in the eyewall region, 5% of the vertical motions were >5 m s −1 . There have been numerous ground-based profiler and multiple Doppler measurements of convection in the tropics and subtropics but fewer measurements over the oceans that have been derived from either

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Chuntao Liu, Earle R. Williams, Edward J. Zipser, and Gary Burns

variations of the fair weather electric field for various seasons. 2. Data and method The TRMM satellite has a non-sun-synchronous 35° inclination orbit covering the tropics and subtropics, with instruments for observing precipitation, clouds, and lightning ( Kummerow et al. 1998 ). Given enough observation time, TRMM data provide detailed information about the diurnal cycles of precipitation and clouds ( Negri et al. 2002 ; Nesbitt and Zipser 2003 ; Liu and Zipser 2008 ). This study uses the TRMM

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Oreste Reale, William K. Lau, Kyu-Myong Kim, and Eugenia Brin

fine structure of tropical cyclogenetic processes, because the organization of several convective centers into a rotating system requires cloud-resolving resolutions, which are not yet possible in real-time global numerical weather prediction models. Despite these limitations, it is nonetheless remarkable that the aforementioned high-resolution global models, with different experimental or operational configurations, display distinct cyclogenetic capabilities in the tropics. Moreover, it is

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John Molinari and David Vollaro

) and during large ambient shear. More than half the sondes represent only two storms, Humberto and Danielle. This should not distort the results, however, because the azimuthal helicity variation noted in MV08 was present in every strongly sheared storm. All but 11 of the sondes were released in tropical cyclones with centers north of 20° latitude. The results of this note may not hold for storms in the deep tropics. MV08 did not include a correction for sonde drift. Such drift could have a

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Joël Arnault and Frank Roux

from an adjustment of the wind field to the pressure decrease induced by convection. In the tropics, because the Coriolis force is not strong enough to lead to a rapid evolution to geostrophic equilibrium, the eddy circulation is therefore convergent and tends to fill up the depression. This is what probably occurred during the continental stage of simulated pre-Helene disturbance. Over the ocean, however, the pressure decrease induced by convection was accompanied by a positive barotropic

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

1. Introduction Large-scale influences on tropical cyclogenesis have been studied for many years. There is general agreement that tropical cyclones form in the tropics or subtropics over sufficiently warm (>26°C) water possessing sufficiently great depth, far enough from the equator that background rotation is sufficient, in regions of high relative humidity, and when vertical wind shear over the depth of the troposphere is relatively small ( Gray 1975 , 1979 ). In addition, tropical cyclones

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