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Hideo Yoshihara

surface boundary layer and the upper levels of the sea downto a depth below the diurnal thermocline. In the surface boundary layer the shear stress and the heat flux areconsidered invariant, and the turbulent diffusivities proposed by Pandolfo are used. For the oceans we essentially use the model due to Munk and Anderson in which a simplification is carried out which decouples theenergy equation from the momentum equations and permits a direct determination of the sensible heat fluxin the ocean from

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James R. Holton

than aconstant static stability model. A twodayer model including both a variable Coriolis parameter and bottomfriction is analyzed. This simple model indicates that both bottom friction and the variation of the Coriolisforce enhance the baroclinic mode.1. Introduction In Part I (Holton, 1965) the role of boundary stressesin transient motions of a stratified rotating fluid in thelaboratory was studied. Mathematical expressions forthe interior circulation forced by vertical mass fluxout of the

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Rong Zhang, Thomas L. Delworth, Rowan Sutton, Daniel L. R. Hodson, Keith W. Dixon, Isaac M. Held, Yochanan Kushnir, John Marshall, Yi Ming, Rym Msadek, Jon Robson, Anthony J. Rosati, MingFang Ting, and Gabriel A. Vecchi

and Atlantic hurricane activity ( Goldenberg et al. 2001 ; Knight et al. 2006 ; Zhang and Delworth 2006 ). In particular, tropical North Atlantic surface warming coincided with above-normal Atlantic hurricane activity during the 1950s, 1960s, and the recent decade. These multidecadal NASST variations are often thought to be associated with Atlantic meridional overturning circulation (AMOC) variability ( Delworth and Mann 2000 ; Latif et al. 2004 ; Knight et al. 2005 ). On the other hand, some

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R. Stuhlmann and G. L. Smith

in the ocean thatfurther depress the thermocline in the eastern Pacificwest of the coast of South America and hence intensifythe sea surface temperature anomalies. On the otherhand, the reverse may happen during northern summerwhen the ITCZ has moved farthest to the north. Nowthe warm sea surface water regions are related to alarge-scale low-level divergence. This change in thelarge-scale circulation pattern again can cause a changein cloudiness but in the opposite direction, which additionally

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P. Berrisford, J. C. Marshall, and A. A. White

McWilliams(1984) have discussed a number of filtered models inisentropic coordinates but not the QG model; Hoskinsand Draghici (1977) had previously examined thesemigeostrophic equations in isentropic coordinates.Thermocline models of ocean gyres (see Welander1971; Huang 1988) use isopycnal PV as a dependentvariable but neglect the contribution of relative vorticity, In a study of stratified flow over isolated topography, Sch'ar and Davies (1988) used an isentropic coordinate version of QGPV, which is

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Ka-Ming Lau

-west overturning favors the largest zonal scale. Chang (1977)further demonstrated the importance of viscousdamping to produce the correct phase speed andvertical scales in the observed low-frequency Kelvinlike oscillations of the forced equatorial waves. Thevariabilities in the amplitude and positions of theWalker circulation are then manifest in the responseof stationary waves to slow variations in heat sourcesand sinks controlled, in part, by the change in surface conditions over the ocean. There are many

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Edwin K. Schneider, Richard S. Lindzen, and Ben P. Kirtman

climatology and the variability of the eastern tropical Pacific SST have proven to be very difficult to simulate correctly with current state-of-the-art coupled ocean–atmosphere general circulation models ( Mechoso et al. 1995 ). Coupled models used in transient climate simulations require large flux corrections, especially in the eastern equatorial Pacific, to correctly simulate the current climatology. For example, Murphy (1995) reports that the annual mean heat flux adjustment applied in the Hadley

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P. Goswami and Rameshan K.

intraseasonal signal is present also in the oceanic circulation. Although in the intraseasonal scale the role of OAC has been less clear, recent analyses of outgoing longwave radiation data (January 1985–April 1991) from International Satellite Cloud Climatology Project (ISCCP) as well as European Centre for Medium-Range Weather Forecasts surface analyses (January 1985–December 1994) indicate strong interaction between ocean and atmosphere at IST ( Jones et al. 1996 ). Other studies ( Shinoda et al. 1998

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Peter J. Webster and Ka Ming W. Lau

stratified fluid. J. Fluid Mech., 37, 643-655.Kraus, E. B., and J. A. Turner, 1967: A one-dimensional model of the seasonal thermocline: II. The general theory and its consequences. Tellus, 19, 98-105.Krishnamurti, T. N., 1971: Tropical east-west circulations during the northern summer. J. Atmos. Sci., 28, 1324-1347.Lahiff, L. N., 1975: A low-latitude atmosphere-ocean climate model. J. At~nos. Sci., 32, 657-674,1084 JOURNAL OF THE ATMOSPHERIC SCIENCES

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Mark A. Cane, Matthias Münnich, and Stephen F. Zebiak

analyze the linearized version of an analytical model, which combines linear ocean dynamics with asimple version of the Bjerknes hypothesis for El Nifio. The ocean is represented by linear shallow water equationson an equatorial beta-plane. It is driven by zonal wind stress,which is assumed to have a fixed spatial form.Stress amplitude is set to be proportional to the thermocline displacement at the eastern boundary. It is shown that, for physically plausible parameter values, the model system can

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