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Mark P. Baldwin, Thomas Birner, Guy Brasseur, John Burrows, Neal Butchart, Rolando Garcia, Marvin Geller, Lesley Gray, Kevin Hamilton, Nili Harnik, Michaela I. Hegglin, Ulrike Langematz, Alan Robock, Kaoru Sato, and Adam A. Scaife

of residual circulation and mixing in the stratosphere and mesosphere. The thick white arrows depict the TEM mass streamfunction as representation of the residual circulation, whereas the wavy orange arrows indicate two-way mixing processes. Both circulation and mixing are mainly induced by wave activity on different scales (planetary to gravity waves). The thick green lines represent stratospheric transport and mixing barriers. Note that the vertical scale compresses the mesosphere above 50 km

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Chih-Pei Chang, Mong-Ming Lu, and Hock Lim

pressure (e.g., Ramage 1971 ; Chang et al. 1979 , 1983 ; Chu and Park 1984 ; Lau and Chang 1987 ; Wu and Chan 1995 ; Zhang et al. 1997 ). The movement of the midlatitude circulation involves basically the advection of relative and planetary vorticity, but the nearly spontaneous freshening of the low-level northeasterly winds in the tropics and their large cross-isobar angles indicate a rapid progression of events on a gravity wave time scale, considerably shorter than that of the advective scale

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Boualem Khouider and Andrew J. Majda

exhibits the wavelike disturbances that have the same features as their linear equivalents, including a reduced phase speed of roughly 17 m s −1 and a front-to-rear vertical tilt in wind, temperature, and heating field. In particular, note that the nonlinear simulation is characterized by packets of synoptic-scale waves moving at about 17 m s −1 and have a planetary-scale wave envelope moving in the opposite direction at a slower speed of 5 to 6 m s −1 , mimicking observed CCWs evolving within the

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Yukari N. Takayabu, George N. Kiladis, and Victor Magaña

. Climate , 22 , 300 – 315 , doi: 10.1175/2008JCLI2340.1 . Lin , X. , and R. H. Johnson , 1996 : Kinematic and thermodynamic characteristics of the flow over the western Pacific warm pool during TOGA COARE . J. Atmos. Sci. , 53 , 695 – 715 , doi: 10.1175/1520-0469(1996)053<0695:KATCOT>2.0.CO;2 . Lindzen , R. S. , 1967 : Planetary waves on beta planes . Mon. Wea. Rev. , 95 , 441 – 451 , doi: 10.1175/1520-0493(1967)095<0441:PWOBP>2.3.CO;2 . Lindzen , R. S. , 1974 : Wave-CISK and

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T. N. Krishnamurti, Ruby Krishnamurti, Anu Simon, Aype Thomas, and Vinay Kumar

larger-scale MJO envelope wave, propagate from east to west with typical speeds on the order of 5° to 7° longitude per day whereas the MJO moves eastward around the globe (360°) in around 40 days. This disparity in space–time scales of the clouds and mesoscales embedded in synoptic scales and the planetary-scale MJO makes it an interesting problem for scale interactions. Basically the important question we raise here is how clouds whose scale is of the order of a few kilometers communicate with the

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Isaac M. Held

uniform mean flow with no vertical shear, in which vertically propagating waves are manifestly present. (Of course, there are many such cases where, in retrospect, one can imagine ways in which the progress of theory might have evolved more logically.) The concept of a vertically propagating Rossby, or “planetary,” wave was not fully appreciated until Charney and Drazin (1961) . It is interesting to speculate how this concept, unknown to Rossby, could have been developed without the benefit of QG

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Andrew J. Majda and Samuel N. Stechmann

1. Introduction In this chapter, the multiscale hierarchy of organized convection will be divided into three broad categories: (i) the MJO on planetary spatial scales (roughly 20 000 km) and intraseasonal time scales (roughly 40 days) ( Lau and Waliser 2005 ; Zhang 2005 ), (ii) convectively coupled equatorial waves (CCW) on equatorial synoptic scales (roughly 2000 km and 4 days) ( Kiladis et al. 2009 ), and (iii) MCS on mesoscales (roughly 200 km and 0.4 days) ( Houze 2004 ). This hierarchy

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Ronald B. Smith

stationary waves to the mountains themselves. One important clue to the source of planetary waves is their wintertime preference. In winter, the high latitudes are have larger static stability (20-3) , a shifted and stronger polar jet, and strengthened local oceanic heat sources, any of which could be important in stationary wave generation. A second clue is the stronger stationary waves in the Northern versus the Southern Hemisphere. It is generally recognized that the Northern Hemisphere has a greater

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Steven K. Esbensen, Jan-Hwa Chu, Wen-wen Tung, and Robert G. Fovell

central and eastern Pacific. Professor Yanai and graduate students Mong-Ming Lu and Victor Magaña calculated lateral energy fluxes by large-scale disturbances in the upper troposphere and found evidence for selective forcing of equatorially trapped planetary waves in the upper troposphere depending on season and the characteristics of waves propagating energy into the tropics ( Yanai and Lu 1983 ; Magaña and Yanai 1995 ). Magaña and Yanai (1991) also presented evidence for a summertime modulation

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Eric D. Maloney and Chidong Zhang

a : Interactions between the boreal summer intraseasonal oscillation and higher-frequency tropical wave activity . Mon. Wea. Rev. , 131 , 945 – 960 , doi: 10.1175/1520-0493(2003)131<0945:IBTBSI>2.0.CO;2 . Straub , K. H. , and G. N. Kiladis , 2003b : Extratropical forcing of convectively coupled Kelvin waves during austral winter . J. Atmos. Sci. , 60 , 526 – 543 , doi: 10.1175/1520-0469(2003)060<0526:EFOCCK>2.0.CO;2 . Straus , D. M. , and R. S. Lindzen , 2000 : Planetary

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