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B. Radhakrishna and T. Narayana Rao

with Low and List (1982) , continuing to McFarquhar (2004) , and to Prat and Barros (2007) have shown that the equilibrium DSD contains MPs (two or three depending on the parameterization scheme employed in their study). They have shown that the MPs are a result of the fragmentation of filaments, sheets, and disks. The observational evidence for MPs came from early measurements of DSD with Joss–Waldvogel disdrometers (JWDs) ( Steiner and Waldvogel 1987 ; Zawadzki and De Agostinho Antonio 1988

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P. F. J. Lermusiaux and A. R. Robinson

1. Introduction Data assimilation (DA) refers to the estimation of oceanic–atmospheric fields by melding sensor data with a model of the dynamics under study. Most DA schemes are rooted in statistical estimation theory: the state of a system is estimated by combining all knowledge of the system, like measurements and theoretical laws or empirical principles, in accord with their respective statistical uncertainty. The present challenge is that the state of the atmosphere and

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Steven E. Koch and Paul B. Dorian

cores of upper-level jets (Gedzelman and Rilling1978; Koch 1979); Fujita (1955) discussed the difficulty of isolatinggravity wave effects upon surface pressure fields fromthose caused concurrently by deep convection. Kochand Golus (1988, hereafter referred to as Part I) showthat the latter objection is particularly relevant for mesoscale waves analyzed primarily with the aid of synoptic observations, which have formed the databasefor nearly all previous studies of such waves. Some988 American

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Chung-Chieh Wang, George Tai-Jen Chen, Tzu-Chin Chen, and Kazuhisa Tsuboki

comparing with Yeh and Chen (2002) , this study also sheds additional insights into the effects of Taiwan topography on convection and precipitation. 2. Data and analysis a. Observational data and analysis Six-hourly gridded regional objective analyses from the Japanese Meteorological Agency (JMA) at 0.25° latitude–longitude resolution at 20 levels during 22–23 May 2002 were used for synoptic discussion and to compare with model output. The regional analysis is performed by the JMA regional spectral

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David H. Bromwich, Lesheng Bai, and Gudmundur G. Bjarnason

from May to September. The annual distribution of precipitation over Iceland is directly dependent on the position of the Icelandic low. The observed mean annual precipitation distribution for 1931–60 is shown in Fig. 10a . This analysis is derived from mostly low elevation station precipitation observations (not corrected for systematic errors, like wind effects) and supplemented by hydrologic observations and snow accumulation measurements for subjective evaluation in areas with no direct

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Paul J. Neiman, Daniel J. Gottas, and Allen B. White

for the rapid changes in gap-flow depth and gap-jet speed along the CRG may be associated with thermodynamic changes well above the gap-flow (e.g., related to mountain wave activity), and may require vertical temperature profiling up to midtropospheric levels ( Mayr et al. 2007 ). In an attempt to address this measurement shortcoming, ESRL is activity pursuing alternative RASS sampling methods, including the use of acoustic sources at multiple radii from the radar antenna, to improve height

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E. J. Zipser

somesquall lines at low levels. The primary data source is measurements taken during aircraft penetrations ofcertain low-latitude squall lines; they are supplemented by satellite data; radar data, surface meteorologicaldata, and soundings ahead of and behind the squall lines. A shallow layer of cool, near-saturated air occupiesthe lowest few hundred meters and is separated by a marked stable layer from a deep layer of highly unsaturated air. The lowest layer is hypothesized to be the product of

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Elinor R. Martin and Richard H. Johnson

better describe the structure, dynamics, and significance of atmospheric bores in the NAM region. Observational measurements collected during NAME from 1 July to 15 August 2004, allow for detailed studies of the structure and dynamical mechanisms of internal bores. Very few observations are routinely available in this region from the operational network; however, data collected during the NAME field campaign have provided an unprecedented high temporal and spatial resolution dataset ( Higgins et al

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George S. Young, Samuel M. Perugini, and C. W. Fairall

measurements: A prototype system us ing realtime spectral computations. J. Atmos. Oceanic Technol., 7, 425-453.Gamache, J. F., and R. A. Houze, Jr., 1983: Water budget of a meso scale convective system in the tropics. J. Atmos. Sci., 40, 1835 1850.Gaynor, J. E., and P. A. Mandics, 1978: Analysis of the tropical marine boundary layer during GATE using acoustic sounder data. Mon. Wea. Rev., 106, 223-232. , and C. F. Ropelewski, 1979: Analysis of the convectively mod ified GATE boundary layer

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Richard H. Johnson and Melville E. Nicholls

composite observations provide a coherent, three-dimensional view of a tropical squall boundarylayer which should prove valuable for models of squall wake recovery.1. Introduction The modification of the planetary boundary layerby downdrafts from deep, precipitating convectivesystems presents a formidable problem for large-scalenumerical weather prediction. In particular, convective parameterization theories, if they are to properlyincorporate important effects of cumulus clouds,must take into

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