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T. N. Krishnamurti

low frequency modes--especially on the time scale of 30to 50 days. It is becoming apparent that modulations of active and inactive spells of the monsoon are relatedto wave motions on this time scale. These MONEX data sets provide a strong signal for monitoring these waves.These wave motions on the planetary scale move eastward; on a more regional scale they move northward overthe monsoon region. Their behavior is illustrated with respect to the onset, active and break monsoons.1. Introductio

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Clark Evans, Kimberly M. Wood, Sim D. Aberson, Heather M. Archambault, Shawn M. Milrad, Lance F. Bosart, Kristen L. Corbosiero, Christopher A. Davis, João R. Dias Pinto, James Doyle, Chris Fogarty, Thomas J. Galarneau Jr., Christian M. Grams, Kyle S. Griffin, John Gyakum, Robert E. Hart, Naoko Kitabatake, Hilke S. Lentink, Ron McTaggart-Cowan, William Perrie, Julian F. D. Quinting, Carolyn A. Reynolds, Michael Riemer, Elizabeth A. Ritchie, Yujuan Sun, and Fuqing Zhang

wind, waves, and precipitation. Jones et al. (2003) stressed the necessity of improving use of existing observations and exploiting new capabilities for understanding ET itself, as well as forecasting the phenomenon, and section 5 summarizes progress in and ongoing needs for both. Section 6 documents advances in the forecasting and analysis of ET. Finally, this review concludes with recommendations for future research. As noted above, this review focuses on ET and its direct impacts. A

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

wavenumber, which measures the number of full wavelengths as one goes around the globe. Planetary-scale Rossby waves are typically characterized by zonal wavenumbers , whereas synoptic-scale Rossby waves are characterized by higher wavenumbers. Another idealized incarnation of a Rossby wave would be a single trough or ridge being equivalent to a single dipole of υ . However, except in very rare cases, a Rossby wave appears neither as a purely sinusoidal circumglobal wave nor as a single trough or ridge

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J. R. Garratt

(at high wind speeds)--see Charnock and Ellison(1967). More recently Kitaigorodskii (1968) and.Kitaigorodskii and Zaslavskii (1974) considered thecase of transitional flow, where fetch and wind durationmight be important, such thatz0g---= f(Co/u.), (6)where Co is the phase velocity of the dominant wave,Co/u. then describing the degree of wave development,or wave age. Observations of z0 and C~)N (10) over the sea will beconsidered in the next section.3. Values of drag

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Daniel Keyser and M. A. Shapiro

/g-effectopposes, but is subordinate to, the curvature effecT: except for very long (planetary) waves. It should be emphasized that the horizontal divergence and con. vergence in the wave pattern in Fig. 29b are associatedprimarily with along-flow variations in curvature. Furthermore, the ageostrophic wind field (4.4) may havea significant nondivergent component, which does notcontribute to the vertical circulation. As an extxemeexample, a symmetric circular vortex, characterizedby constant curvature on an jZplane

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Roland A. Madden and Paul R. Julian

a: Wave-CISK in the Tropics. J. Atmos. Sci., 31, 156-179. , 1974b: Wave-CISK and tropical spectra. J. Atmos. Sci., 31, 1447-1449.Lorenc, A. C., 1984: The evolution of planetary-scale 200-mb diver gent flow during the FGGE year. Quart. J. Roy. Meteor. Soc., 110, 427-441.Luther, D. S., 1980: Observations of long period waves in the tropical oceans and atmosphere. PhD. thesis, Massachusetts Institute of Technology-Woods Hole Oceanographic Institution, 210 pp.McBride, J. L., 1983

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Tammy M. Weckwerth and David B. Parsons

two-dimensional arguments, while boundaries in nature exhibit significant three-dimensional structure. Horizontal wave patterns thought to be driven by shearing instabilities have been observed along many boundary layer convergence zones (e.g., Hobbs and Persson 1982 ; McCarthy and Koch 1982 ; Carbone 1982 , 1983 ; Parsons and Hobbs 1983 ; Mueller and Carbone 1987 ; Wakimoto and Wilson 1989 ; Wilson et al. 1992 ; Weckwerth and Wakimoto 1992 ; Kingsmill 1995 ). Detailed Doppler radar

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Richard A. Anthes

. J. Perkey and C. W. Kreitzberg, 1981: A numerical case study of the squall line of 6 May 1975. J. Atmos. Sci., 38, 1601-1615. , and ........ , 1982: A numerical case study of the effects of latent heating on a developing wave cyclone. J./ltmos. Sci., 39, 1555-1570.Chang S. W., 1979: An efficient parameterization of Convective and nonconvective planetary boundary layers for use in nu merical models. J./lppl. Meteor, 18, 1205-1215.Collins, W. C., 1980: A comparison of explicit and semi

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Robert A. Houze Jr.

-state vortex is assumed to have a maximum of vorticity at its center, with the vorticity decreasing monotonically with radius. The idealized vortex is initially disturbed by a wavenumber-2 asymmetry, and in time, the asymmetry takes on the shape of two major spiral bands, as seen in Fig. 38 . These bands are packets of vortex Rossby waves , which are a generalized version of the planetary-scale Rossby waves that distort the midlatitude westerly jet stream ( Holton 2004 , 213–217). The comparison to

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Clifford Mass and Brigid Dotson

windstorms have come in pairs or even triplets during periods of favorable long-wave structure over the eastern Pacific (specifically, a long-wave trough), and this period possessed such back-to-back windstorms, with the first producing the most serious losses. The initial low center followed a course similar to the Columbus Day Storm except that it tracked about 140 km farther offshore, with landfall on central Vancouver Island ( Fig. 2 ). Over the eastern Pacific this storm intensified at an

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