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L. J. Gray, S. T. Rumbold, and K. P. Shine

discrepancy between the 11-yr SC estimates from the SSU/MSU and the National Centers for Environmental Prediction (NCEP)–National Center for Atmospheric Research (NCAR) and 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) reanalyses. An additional output from the above calculations is the radiative forcing at the tropopause, which includes the so-called instantaneous radiative forcing due to the changes in irradiance and ozone, and also the effect of the FDH

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Linda Forster, Claudia Emde, Bernhard Mayer, and Simon Unterstrasser

1. Introduction The global radiative forcing (RF) of line-shaped contrails and contrail cirrus calculated by general circulation models (GCMs) exhibits a high level of uncertainty. These uncertainties arise mainly from the radiative transfer models used to calculate the contrail RF as well as from the contrail parameterization and its inherent assumptions employed to represent contrail properties for large grid boxes rather than for individual contrails. A recent study by Frömming et al. (2011

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Carynelisa Erlick, Jonathan P. D. Abbatt, and Yinon Rudich

1. Introduction Ammonium sulfate (AS)–containing aerosols are among the most common aerosols in the troposphere, contributing significantly to direct solar radiative forcing of the climate (e.g., Forster et al. 2007 ). An important consideration in assessing their direct radiative forcing is their change in size and composition due to uptake of water at different relative humidities, which exhibits a well-known hysteresis pattern. As the relative humidity increases from 0%, a crystalline AS

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Thomas R. Krismer and Marco A. Giorgetta

changing background flow ( Giorgetta et al. 2006 ). Giorgetta et al. (2006) presented a climatology of the forcing of the QBO based on an operational GCM, showing that parameterized small-scale gravity waves are as important in forcing the QBO as the resolved waves with zonal wavenumbers up to 42. The spectral distribution of the QBO wave forcing has been presented by Kawatani et al. (2010a) and Evan et al. (2012) ; however, because of the computational costs of their high-resolution experiments

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Isidoro Orlanski and Silvina Solman

1. Introduction The role and dynamics of large stationary and quasi-stationary atmospheric circulation has stimulated considerable discussion in the scientific community. Since the pioneering work of Charney and Eliassen (1949) , Bolin (1950) , and Smagorinsky (1953) , there have been numerous studies on the effects of large-scale orography and thermal forcing on atmospheric flows. Charney and Eliassen emphasized the importance of orography on large-scale stationary disturbances over the

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Cegeon J. Chan and R. Alan Plumb

1. Introduction Several previous studies (e.g., Song and Robinson 2004 ; Polvani and Kushner 2002 , hereafter PK02 ; Kushner and Polvani 2004 , hereafter KP04 ; Son and Lee 2006 ; Ring and Plumb 2007 , 2008 ) have described the relationship between external forcings and the climatological response in model simulations. With extratropical forcings, the spatial structure of the response is dominated by the model’s “annular modes” ( Thompson and Wallace 2000 ; Lorenz and Hartmann 2001

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O. E. García, A. M. Díaz, F. J. Expósito, J. P. Díaz, A. Redondas, and T. Sasaki

1999 ; Arimoto et al. 2006 ; Shen et al. 2006 ) and hence different radiative traces. In particular, Sokolik and Toon (1999) found that aerosol optical properties are very sensitive to the individual minerals and their mixtures in dust composition, even modifying the net effect (i.e., the sign) of mineral dust radiative forcing. Thus, the present study examines the impact of the natural mineral dust on the UV energy transfer by analyzing the influence of the source region. 2. Instrumentation

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Gang Chen and Pablo Zurita-Gotor

2004 ; Haigh et al. 2005 ). However, the mechanism through which increased lower-stratospheric winds shift the tropospheric jet remains obscure. Previous studies have mainly focused on the effects of the eddy-induced zonal forcings and the vertical wind shears in the lower stratosphere. These zonal forcings can induce a meridional residual circulation that extends downward and closes in the planetary boundary layer. This provides a zonally symmetric pathway to redistribute momentum in the vertical

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Amanda C. Maycock, Christopher J. Smith, Alexandru Rap, and Owain Rutherford

1. Introduction Radiative forcing (RF) quantifies the change in Earth’s energy balance from an imposed perturbation of natural or anthropogenic origin (e.g., IPCC 1990 ). Given knowledge of climate feedback processes, RF is a useful measure to predict the eventual global mean surface temperature change resulting from a climate perturbation (e.g., Hansen et al. 1985 ); as a consequence, it is a common measure of interest for climate science ( Shine and Forster 1999 ). Various incarnations of

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Sarah D. Ditchek, John Molinari, and David Vollaro

composite nondeveloping storm with its diffuse eddy fluxes did not intensify. Most importantly, removing the eddy momentum fluxes from the developing storm prevented it from intensifying, even after 20 days. The authors hypothesized that a deep balanced response to these fluxes created enhanced radial circulation in the storm that contributed to its development. In this framework, outflow eddies provide meaningful forcing of tropical cyclone intensification. One limitation of the Pfeffer and Challa

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