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Ming Cai and Ka-Kit Tung

1. Introduction Following the pioneering work of Manabe and Wetherald (1975) and Manabe (1983) , Hansen et al. (1984) performed general circulation model (GCM) experiments that include doubling CO 2 and increasing the solar constant by 2%—“forcings of roughly equal magnitude”—to study climate sensitivity. The surface temperature response was found to be remarkably similar in magnitude and in seasonal and meridional variations. This is in spite of the fact that solar radiative heating

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Jin-Song von Storch

1. Introduction In recent years, climate variations on long timescales have drawn more and more attention from researchers. Concerning the atmospheric variability, James and James (1989) considered an integration of about 100 yr obtained with a simplified atmospheric circulation model, with the annual cycle being the only external forcing of the system. They found that the atmospheric flow can be variable on timescales of about 10–40 yr. Several other studies followed, again using long

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Harry H. Hendon and Dennis L. Hartmann

15DECEMBER 1985 HARRY H. HENDON AND DENNIS L. HARTMANN 2783Variability in a Nonlinear Model of the Atmosphere with Zonally Symmetric Forcing HARRY H. HENDON AND DENNIS L. HARTMANNDepartment of Atmospheric Sciences, AK-40, University of Washington, Seattle, WA 98195(Manuscript received 28 January 1985, in final form 15 July 1985)ABSTRACT The variability in a two-level nonlinear atmospheric model is examined. The

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H-L. Liu

the statistical behavior of simplified one-dimensional (in the vertical direction) systems with the following features: 1) They are driven by a force that is random in space and time, which can be regarded as an approximation to various perturbations, including but not limited to gravity waves; 2) The systems undergo diffusive transport. Two scenarios of diffusive transport are considered here, with the diffusive coefficient being uniform, and being dependent on the gradient of the field

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Natalia Calvo and Rolando R. Garcia

stratosphere. GR08 suggested that these changes are linked to trends in the zonal-mean zonal wind structure of the upper troposphere and lower stratosphere, which in turn follow from changes in the zonal-mean temperature distribution caused by the increase in GHGs. Further analysis of the Eliassen–Palm (EP) flux and its divergence revealed that trends in wave driving in the lower stratosphere, below about 20 km, were due mainly to forcing by waves resolved explicitly in the model, the influence of

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Warren P. Smith, Melville E. Nicholls, and Roger A. Pielke Sr.

in the early morning and is weakest in the afternoon local time ( Jacobson and Gray 1976 ). This has been attributed to both a nocturnal differential radiative forcing between cloud structures and their relatively clear-sky surroundings ( Gray and Jacobson 1977 ) and to nocturnal longwave-induced destabilization ( Xu and Randall 1995 ). Convective destabilization of clouds due to longwave radiation is sensitive to the cloud quantity ( Godbole 1973 ) and has been linked to the intensification of

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Matthew Newman and Prashant D. Sardeshmukh

particularly important? Clearly, the statistics of low-frequency (>10 day) variability can also depend upon the annual cycle of the forcing itself (such as synoptic-eddy feedbacks and anomalous tropical heating). Nevertheless, modeling studies suggest that at least part of the annual cycle of the low-frequency statistics could be due to the annual cycle of the mean flow. For example, the response to steady anomalous forcing in a two-level model with zonally symmetric flow has been shown to depend strongly

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John M. Peters

motion w within convective updrafts remains an elusive goal. Perhaps the simplest conceptual explanation for cumulus updrafts is that the air within them rises because it experiences an upward buoyancy force by virtue of the air within the updraft being warmer and less dense than its surroundings. In the atmospheric sciences, the buoyancy force B is formally expressed as the ratio of the density of a parcel of air to the density of its surrounding environment: , where g is gravity, is the

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Aditi Sheshadri, R. Alan Plumb, and Edwin P. Gerber

; their timing is variable around or after the spring equinox (being delayed by around 2 months with respect to equinox in the Southern Hemisphere), with the early events being the most active ( Black and McDaniel 2007a , b ; Hu et al. 2014b ). While some part of this wintertime variability is undoubtedly a reflection of variability in tropospheric wave forcing, it is clear from modeling studies that such variability can arise spontaneously as a consequence of the dynamical interaction between waves

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Tomoaki Nishizawa, Shoji Asano, Akihiro Uchiyama, and Akihiro Yamazaki

present paper, we shall concentrate on aerosol direct effects on the solar radiation on the earth's surface. Radiative forcing is an important parameter in assessing the aerosol direct effect on the radiation budget, and consequently many investigators have made estimates of aerosol radiative forcing. These estimates are generally made by model simulations (e.g., Charlson et al. 1992 ; Kiehl and Briegleb 1993 ; Mitchell et al. 1995 ). Recently, extensive and sophisticated surface aerosol

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