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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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C. W. Fairall, Taneil Uttal, Duane Hazen, Jeffrey Hare, Meghan F. Cronin, Nicholas Bond, and Dana E. Veron

). This paper complements two recent papers featuring analysis of the TAO buoy observations along 95° and 110°W: studies of the annual cycle of cloud radiative forcing at the surface ( Cronin et al. 2006a ) and the annual cycle of sensible and latent heat fluxes ( Cronin et al. 2006b ). The first paper found disagreements as large as 100 W m −2 between buoy radiative flux observations and NWP reanalysis values; the second paper found disagreements of the same order for latent heat flux. The

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Lauren E. Padilla, Geoffrey K. Vallis, and Clarence W. Rowley

1. Introduction The steady-state response of the global-mean, near-surface temperature to an increase in greenhouse gas concentrations (e.g., a doubling of CO 2 levels) is given, definitionally, by the equilibrium climate sensitivity (ECS), and this is evidently an unambiguous and convenient measure of the sensitivity of the climate system to external forcing. However, given the long time scales involved in bringing the ocean to equilibrium, the ECS may only be realized on a time scale of many

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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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Jonathan M. Winter and Elfatih A. B. Eltahir

. Each numerical experiment was initialized 1 April 1994 and allowed to spin up for 21 months. The domain was centered at 40°N, 95°W and spanned 100 points zonally, 60 points meridionally with a horizontal grid spacing of 60 km ( Fig. 2 ). The 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) dataset ( Uppala et al. 2005 ) was used to force the boundaries under the exponential relaxation of Davies and Turner (1977) . SSTs were prescribed using the National Oceanic

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Yi Song and Yongqiang Yu

1. Introduction Both atmospheric and oceanic circulations exhibit prominent fluctuations on decadal and multidecadal time scales. Despite rising concentrations of atmospheric greenhouse gases (GHGs), the global mean surface air temperature (SAT) has remained flat for the past 16 years (i.e., the recent warming hiatus; Easterling and Wehner 2009 ). This observation challenges the prevailing view that anthropogenic forcing leads to global warming. An interpretation regarding the hiatus is the

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Jian Yuan, Dennis L. Hartmann, and Robert Wood

called cloud radiative forcing (CRF), may respond to external influences on the climate system and thereby constitute a substantial climate feedback (e.g., Schneider 1972 ; Cess et al. 1996 ). The tropical climate system response to an external perturbation is an important outstanding problem, and cloud feedback still stands as a large source of uncertainty in predicting future climate ( Cess et al. 2001b ; Stephens 2005 ; Solomon et al. 2007 ). Clouds respond both to large-scale dynamical

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Jérôme Sirven, Christophe Herbaut, Julie Deshayes, and Claude Frankignoul

1. Introduction There is increasing evidence that the decadal variability of the midlatitude ocean (e.g., Kushnir 1994 ; Deser et al. 1999 ) primarily reflects the variability of the atmosphere via stochastic wind stress forcing. Considering a stratified model with an open western boundary, Frankignoul et al. (1997) found that the oceanic response was largest at decadal frequency, but no spectral peak appeared (see also Sirven et al. 2002 ). LaCasce (2000) and Cessi and Louazel (2001

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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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Timothy Andrews

1. Introduction Radiative forcings have long been used to quantify and rank the drivers of climate change (e.g., Hansen et al. 1997 ; Shine and Forster 1999 ). In climate models, radiative forcings can help us understand why different models differ in their simulations of the past and future. For example, Forster et al. (2013) found the intermodel spread in the global surface temperature change across phase 5 of the Coupled Model Intercomparison Project (CMIP5) ( Taylor et al. 2012

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