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Alexey Fedorov, Marcelo Barreiro, Giulio Boccaletti, Ronald Pacanowski, and S. George Philander

meridional overturning circulation associated with the surface temperature and salinity gradients and involving the deep ocean. That a freshening in high latitudes can lead to a shutdown of the thermohaline circulation is the topic of many papers (e.g., Manabe and Stouffer 1995 , 2000 ; Rahmstorf 1995 ; Stocker and Schmittner 1997 ; Alley et al. 2003 ; Seidov and Haupt 2002 , 2003 , and many others). The impact of such a shutdown on the earth’s surface temperatures is prominent mainly over the

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Morris A. Bender, Hans A. Panofsky, and C. A. Peslen

NOVEMBER1976 M. A. BENDER, H. A. PANOFSKY AND C. A. PESLEN 1193Temperature Gradients and Clear-Air Turbulence Probabilities MORRIS A. BENDERl, HANS A. PANOFSKY AND C. A. PESLEN2 Department of Meteorology, The Pennsylvania State University, University Park 16802 (Manuscript received 1 March 1976, in revised form 7 October 1976) ABSTRACT From the end of October 1973 to the beginning of

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David Walland and Ian Simmonds

temperature get out of phase. The rates of warming and cooling between the two annual cycles differ as well for complex energy balance reasons. As a result, the meridional temperature gradients in the midtroposphere between approximately 50°S and the Antarctic continent display a strong half-yearly wave. These meridional temperature gradients are then thought to be directly associated with changes in baroclinicity, which leads to a strong half-yearly wave in surface pressure ( van Loon 1967 ). It should

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Maarten H. P. Ambaum and Panos J. Athanasiadis

1. Introduction In this paper we examine the linear response of a uniform horizontal temperature gradient to heating. Under certain assumptions on the vertical structure of the heating field, linear perturbations satisfy a modified form of surface quasigeostrophic dynamics. The system is the thermal analog to the Charney–Eliassen system of orographically forced barotropic Rossby waves ( Charney and Eliassen 1949 ; Held 1983 ) and a surface-only variant of the system studied by Smagorinsky

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Daniel A. Shaevitz and Adam H. Sobel

1. Introduction Since horizontal temperature gradients are small in the Tropics, it seems reasonable to take them to be zero as a simplifying assumption in theoretical or idealized modeling studies. This has been done in a number of “two column” models that represent the Tropics by two homogeneous regions, representing the ascending and descending branches of the Hadley or Walker circulations ( Pierrehumbert 1995 ; Miller 1997 ; Larson et al. 1999 ; Clement and Seager 1999 ; Kelly and

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Andrew Hoell and Chris Funk

the low-level circulation and convergence over the tropical Pacific Ocean. Though in this work the secular SST trend was removed and the focus is placed on the anomalous SST gradient associated with ENSO, the results presented in the following indicate increased tropical divergence and modifications to the western branch of the Walker circulation associated with strong WPG ENSO events. Displayed in Fig. 9 are vertical sections of equatorial temperature (shading), zonal wind (vectors), and

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L. M. Polvani and A. H. Sobel

1. Introduction Balance models, such as the quasigeostrophic, are at the very foundation of much of our understanding of extratropical atmospheric dynamics. The so-called weak temperature gradient (WTG) approximation has been proposed ( Sobel and Bretherton 2000 ; Sobel et al. 2001 ; Bretherton and Sobel 2002, manuscript submitted to J. Atmos. Sci., hereafter BS02) as a balance model for the Tropics. WTG is somewhat distinct from other balance models in that it does not assume the vorticity

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Christina Karamperidou, Francesco Cioffi, and Upmanu Lall

1. Introduction The midlatitude storm track is a factor in determining moisture and heat transport associated with enhanced precipitation events. In a seminal paper, Lorenz (1984) developed a model—the Lorenz-1984 (L84)—for the jet stream and the superposed eddies that are forced by the equator-to-pole temperature gradient (EPG) and the ocean–land temperature contrast (OLC). The model exhibits chaos and intransitivity, depending on the combination of the EPG and OLC, and its properties have

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Dale B. Haidvogel and Isaac M. Held

2644 JOURHAL OF THE ATMOSPHERIC SCIENCES VOLVM-3?Homogeneous Quasi-Geostrophic Turbulence Driven by a Uniform Temperature Gradient DALE B. HAIDVOGELDepartment of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02545 ISAAC M. HELDGeophysical Fluid Dynamics Laboratory/NOAA, Princeton Univ,ersity, Princeton, NJ 08540(Manuscript received 24 March 1980

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Adam H. Sobel, Johan Nilsson, and Lorenzo M. Polvani

1. Introduction a. Background Horizontal density and temperature gradients are very small in the Tropics. The well-known consequence of this is that, on large scales, the dominant balance in the temperature equation is between heating and vertical advection of potential temperature. A tropical heat source causes vertical motion and an associated horizontal flow but only small temperature changes. A number of studies have neglected horizontal temperature variations as a simplifying assumption in

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