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Eun-Pa Lim, Harry H. Hendon, Amy H. Butler, David W. J. Thompson, Zachary D. Lawrence, Adam A. Scaife, Theodore G. Shepherd, Inna Polichtchouk, Hisashi Nakamura, Chiaki Kobayashi, Ruth Comer, Lawrence Coy, Andrew Dowdy, Rene D. Garreaud, Paul A. Newman, and Guomin Wang

follow the canonical evolution of the upper-stratospheric winds and planetary wave activity for springtime polar vortex weakening, but the poleward heat flux anomalies at 100 hPa were extraordinarily strong in August and September 2019 ( Fig. 4d ), which was consistent with the resultant record weakening of the polar vortex. More details of the increased poleward heat flux during 2019 are provided in Fig. 5a , which displays the standardized amplitudes of the wave-1 poleward heat flux anomalies

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Albert V. Carlin

A clear-cut case of dispersion of energy downstream in the mid-tropospheric long-wave pattern during the first two weeks of November 1951 is examined with the help of plots of meridional wind components. The dispersion could be traced over more than half the hemisphere traveling with a speed about twice that of the zonal wind at 700-mb. Calculations of group velocity based on Rossby's work show good agreement with observed values of the speed of dispersion.

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Mitchell W. Moncrieff, Duane E. Waliser, Martin J. Miller, Melvyn A. Shapiro, Ghassem R. Asrar, and James Caughey

transported upward into the atmosphere. From there, the heat is radiated back to space and the moisture may condense and form clouds. Some of the condensate grows large enough to fall back to Earth's surface as precipitation. In this regard, moist convection plays a crucial role in the energy and water cycles of the tropics as well as the variability of the tropical climate system. In concert with its effects on the tropics per se, moist convection can generate planetary (Rossby) waves, which affect

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John W. Nielsen-Gammon

A 20-yr loop of the global tropopause, defined in terms of potential vorticity (PV), is constructed using the NCEP–NCAR reanalysis dataset. This method of visualizing observed upper-tropospheric dynamics is useful for studying a wide range of phenomena. Examples are given of the structure of jet streams and planetary-scale tropopause folds, the propagation of a high-amplitude Rossby wave packet partway around a hemisphere, several subtropical wave breaking events, the similarities between exceptional cases of rapid cyclogenesis, favorable regions for cross-equatorial propagation of Rossby waves, the annual cycle of the tropical tropopause, the structure of the Tibetan anticyclone and equatorial easterly jet associated with the Asian monsoon, the meridional structure of the upper branch of the Hadley cell, the interaction of a hurricane and midlatitude trough to form the “Perfect Storm,” and the upper-tropospheric PV changes associated with El Niño and La Niña.

Plumes of anticyclonic potential vorticity are frequently seen to be pulled from the subtropical reservoir and roll up into large anticyclones. These previously undescribed plumes may be particularly relevant to jet streak dynamics and stratosphere-troposphere exchange.

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L. Cavaleri, B. Fox-Kemper, and M. Hemer

WHERE THE INTERACTION BEGINS. Gravity wind-wave–driven processes at the ocean surface—including radiation fluxes and energy, mass, and momentum exchanges—play an important role in the coupled climate system. Erik Mollo-Christensen of Massachusetts Institute of Technology (MIT) and builder of one of the first air–sea interaction buoys used to tell his students: “Meteorologists consider the ocean as a wet surface. Oceanographers consider the atmosphere as a place where wind blows.” Of course

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Roland A. Madden

and observations of wave periods are shown for comparison. 1 THEORETICAL PREDICTIONS OF NORMAL-MODE ROSSBY–HAURWITZ WAVES. Rossby et al. (1939) isolated the basic dynamics that control an important class of the normal modes: the “waves of the second class,” or, in his words, “planetary waves.” Haurwitz (1940a , b ) extended Rossby’s treatment thus the reference “normal-mode Rossby–Haurwitz waves.” The theory of normal modes in the ocean and atmosphere has a long history dating back to the

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Samuel P. Lillo, David B. Parsons, and Malaquias Peña

( Wallace and Gutzler 1981 ), in which a planetary-scale wave response emanates northeastward from enhanced convection over the equatorial Pacific. As a result of this filtering effect, the winters with an augmented subtropical jet would be dominated by low-wavenumber perturbations in the midlatitudes. In stark contrast to this painting of a canonical strong El Niño, the winter of 2015/16 was characterized by a weaker thermal gradient in SSTs due to the warm waters across portions of the subtropics and

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Jennifer Fowler, Junhong Wang, Deborah Ross, Thomas Colligan, and Jaxen Godfrey

. Sounding profiles of temperature, pressure, wind speed, and wind direction can indicate another potential atmospheric phenomenon generated during eclipses: tropospheric and stratospheric gravity (buoyancy) waves. An attempt at obtaining these measurements was made during the 2015 U.K. solar eclipse studies by Marlton et al. (2016) that concluded, “it is impossible to deduce whether the eclipse generated any gravity waves…Further work might concentrate on making similar observations during a future

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Edwin P. Gerber, Amy Butler, Natalia Calvo, Andrew Charlton-Perez, Marco Giorgetta, Elisa Manzini, Judith Perlwitz, Lorenzo M. Polvani, Fabrizio Sassi, Adam A. Scaife, Tiffany A. Shaw, Seok-Woo Son, and Shingo Watanabe

(1949) and Dobson (1956) revealed that the stratosphere actively circulates from the equator to the poles, a meridional overturning now known as the Brewer–Dobson circulation. Key advances in stratospheric dynamics in the 1960s and 1970s linked stratospheric variability to tropospheric phenomena. Direct interactions are primarily at the extremes of the spatial spectrum, involving planetary- scale waves and small-scale gravity waves, but notably not synoptic waves (e.g. Charney and Drazin 1961

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Todd P. Lane, Robert D. Sharman, Stanley B. Trier, Robert G. Fovell, and John K. Williams

turbulence by thunderstorms, and identify the outstanding problems; 2) highlight the inadequacies in current methods for avoidance of thunderstorm-generated turbulence and motivate the development of new turbulence avoidance guidelines; and 3) demonstrate the capabilities of state-of-the-art forecast models that could be utilized for explicit turbulence predictions. Of the many sources of turbulence that affect aviation (e.g., wind shear, jet streams, fronts, mountain waves, etc.), deep convective clouds

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