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Le Kuai, Run-Lie Shia, Xun Jiang, Ka Kit Tung, and Yuk L. Yung

period of the QBO averages about 28 months but is known to have interannual variations of a few months about the average. While it is not surprising for this phenomenon arising from wave–mean flow interaction to have a variable period, the possibility that it could be affected by external forcing such as the 11-yr solar cycle (SC) is intriguing. Using radiosonde data from the Free University of Berlin (FUB) near the equator at 45 hPa between 1956 and 1996, Salby and Callaghan (2000) found that the

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Robert Gall, Richard Blakeslee, and Richard C. J. Somerville

1692 JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUM-36Cyclone-Scale Forcing of U!tralong Waves ROBERT GALL AND RICHARD BLAKESLEEInstitute of Atmospheric Physics, The University of Arizona, Tucson, AZ 85721 RICHARD C. J. SOMERVILLENational Center for Atmospheric Research~, Boulder, CO 80307(Manuscript received 26 December 1978; in final form 4 May 1979)ABSTRACT A numerical experiment is

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Werner Metz

1 SEPTEMBER 1987WERNER METZ2407Transient Eddy Forcing of Low-Frequency Atmospheric VariabilityWERNER METZMeteorological Institute, University of M-nchen, Federal Republic of Germany(Manuscript received 19 August 1986, in final form 16 February 1987)ABSTRACTThis paper is concerned with the forcing of the low-frequency variability (10 days up to 3 months) of thebarotropic planetary waves (wavenumbers 1 to 4) for wintertime conditions in the Northern Hemisphere. Inparticular, the forcing by the

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J. F. Scinocca and P. H. Haynes

weak, a greater proportion of the planetary wave activity in the wintertime stratosphere is associated with travelling, rather than stationary, disturbances (e.g., Randel 1987 ; Manney et al. 1991 ; Yamazaki and Mechoso 1985 ; Mechoso et al. 1988 ). Another important tropospheric source of planetary wave forcing is likely to be associated with synoptic-scale weather systems. Only the largest scale disturbances can propagate upward into the stratosphere. While the weather systems themselves have

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Nicholas M. J. Hall

1. Introduction There are a multitude of different approaches to modeling climate perturbations. Often the approaches are complementary. A comprehensive general circulation model (GCM) might simulate the observed climate realistically using principles that are as physically based as possible. This engenders a certain amount of confidence in the GCM’s ability to simulate perturbations to the climate, whether they arise from anomalous external forcing or internal variability. However, GCMs are

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Douglas A. Stewart

2710 JOURNAL OF THE ATMOSPHERIC SCIENCES VOL. 50, No. 16Persistent Anomaly Forcing in a Two-Level Global Circulation Model DOUGLAS A. STEWARTEnvironmental Dynamics Research, Inc., Miami, Florida(Manuscript received 29 January 1992, in final form 26 November 1992) ABSTRACT Perpetual January data from a simple global two-level model are used to diagnose the forcing of the

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Max Popp, Hauke Schmidt, and Jochem Marotzke

1. Introduction In the 1960s, the idea was advanced that, under strong radiative forcing, a runaway water vapor feedback may occur, which may lead to the evaporation of all oceans on an Earthlike planet (e.g., Gold 1964 ; Komabyashi 1967 ; Ingersoll 1969 )—the runaway greenhouse. The idea was used to explain how Venus could have lost most of its water and could have ended up with the inhospitable atmosphere that it has today. Even though 50 years have passed, the role of clouds in the

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Gunnar Myhre, Frode Stordal, Tore F. Berglen, Jostein K. Sundet, and Ivar S. A. Isaksen

1. Introduction Several global studies of the direct effect of sulfate aerosols have been performed with large differences in the estimates of the radiative forcing ( Myhre et al. 1998 ; Haywood and Boucher 2000 ; Adams et al. 2001 ; Houghton et al. 2001 ). In addition to uncertainties in the global burden of sulfate, uncertainties in the forcing have several causes. First, there are uncertainties connected to the optical properties of sulfate aerosols. The optical properties adopted in the

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Jun Zhai and William Boos

of monsoon dynamics. In the past 30 years, multiple theoretical advances made in understanding Earth’s Hadley circulation have been extended to solstice-like conditions representative of monsoons. Held and Hou (1980) developed an axisymmetric 1 theory for the strength and meridional extent of the annual-mean Hadley circulation, and Lindzen and Hou (1988) extended this theory to cross-equatorial flow driven by off-equatorial thermal forcings. Central to this axisymmetric theory is the idea

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Jadwiga H. Beres

1. Introduction Parameterization of gravity wave drag force (GWD) is critical to the proper representation of the circulations of the middle and upper atmosphere in general circulation models (GCMs; e.g., Lindzen 1981 ; Boville 1995 ). Parameterized GWD is proportional to the vertical divergence of momentum flux carried by the spectrum of upward-propagating gravity waves specified in the model. Proper representation of this quantity is dependent on the specification of the gravity wave phase

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