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J. David Neelin, Zheng Hao, and Fei-Fei Jin

time scale is fairy long, so r ~ I is a usefulapproximation [r = (250 days)-~ yields nondimensional r = 0.25 ] and atmospheric length scales are orderof 10- so a = L~/(2L~) ~ 0.05, which is even smallerthan r. For a mode with small growth rate and frequency, a ~ 1, the ocean comes into Sverdrup balanceto O(~2) in thermocline depth and O(-) in currents,as discussed in both N and C, yielding Eq. (50) of N[Eq. (1) of C], valid to O[max(qb2, qba)], for he, theequatorial thermocline depth: 0xhe

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Tim Li, Bin Wang, C-P. Chang, and Yongsheng Zhang

-equatorial monsoonal circulation. At the equator, the annual mean wind is easterly in the Pacific but weaker westerly in the IO. Such a difference results in opposite thermocline gradients across the two ocean basins ( Fig. 3 ). The reversal of the basic-state wind and zonal thermocline gradient in the IO implies that the effect of equatorial ocean waves might differ from the Pacific counterpart. The schematic diagram of Fig. 4 illustrates how the wave effect could be different. In the Pacific, an El Niño

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Amy C. Clement

1. Introduction The mean meridional atmospheric circulation in the Tropics is dominated by the well-known Hadley circulation, which was first described by Hadley (1735) . His depiction of the annual mean circulation consisted of rising motion on the equator and subsidence in the subtropics and has been confirmed with global radiosonde data and multiple reanalysis products ( Oort and Yienger 1996 ; Waliser et al. 1999 ). From month to month, however, the Hadley circulation can look quite

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Zengxi Zhou and James A. Carton

. Ocean modeling studies attempting to simulate seasonal and interannual SST have generally been required to include this process ( Seager et al. 1988 ; Giese and Cayan 1993 ; Koberle and Philander 1994 ; Carton et al. 1996 ). Similarly, full coupled atmosphere–ocean general circulation models include both wind stress and latent heating. Wind speed anomalies impact the moisture exchange between the oceanic and atmospheric boundary layers. The moisture exchange not only affects SST (WESST process

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S. G. H. Philander

the two constitute theSouthern Oscillation. The coherence of the fluctuations in the meteorological parameters shown in Fig. 1 can readily be explained by assuming that large-scale motion in thetropical atmosphere corresponds primarily to a directthermal circulation. In the Pacific Ocean the importantregions of heating are the lntertropical ConvergenceZone (ITCZ), the South Pacific Convergence Zone(SPCZ) and especially the convective zone over themaritime continent of the western tropical

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Paul C. F. van der Vaart, Henk A. Dijkstra, and Fei Fei Jin

resulting mode has the property that the zonally averaged thermocline anomaly and the eastern Pacific SST anomaly are not in phase. At the transition phase of zero SST anomaly, the average thermocline depth is shallower or deeper than its climatological value. Hence, within one cycle of the oscillation the equatorial heat content is discharged and recharged once. These features have been observed in data ( Wyrtki 1975 ) and in models ( Cane 1992 ) and have led to a complementary view of the ENSO mode as

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Yajuan Song, Fangli Qiao, and Zhenya Song

et al. 1996 ; Wu et al. 1999 , 2000 ; Wu 2003 ). As a consequence, the differential heating itself cannot directly drive monsoons of observed amplitude and the oppositely directed circulations in the lower and upper troposphere. To drive monsoons of the observed amplitude and structure, deep latent heating is needed. The low-level circulation directly driven by differential heating brings a large amount of moisture from the ocean to the land, which induces deep thermal heating over the land

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S. G. H. Philander, T. Yamagata, and R. C. Pacanowski

, in final form I November 1983)ABSTRACT During El Nifio Southern Oscillation events modest anomalies amplify spatially and temporally until theentire tropical Pacific Ocean and the global atmospheric circulation arc affected. Unstable interactions betweenthe ocean and atmosphere could cause this amplification when the release of latent heat by the ocean affectsthe such a manner that the altered surface winds induce the further release of latent heat.Coupled shallow water models

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Fei-Fei Jin

dynamics ( Schopf and Suarez 1990 ; CMZ; Schneider et al. 1995 ). For example, at the so-called fast-SST limit, which assumes the equatorial SST anomaly to be in quasi-equilibrium with subsurface thermocline fluctuation, CMZ discovered that the coupled process modifies the ocean basin modes ( Cane and Moore 1981 ) to form a coupled wave oscillator described by mapping equations. In fact, CMZ showed that the BH delayed oscillator is an approximation to the coupled wave oscillator at the fast-SST limit

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Andrew Roberts, John Guckenheimer, Esther Widiasih, Axel Timmermann, and Christopher K. R. T. Jones

can be described in terms of the recharge oscillator paradigm ( Jin 1997 ). The key regions for ENSO physics are the western and eastern equatorial Pacific. The important dynamical variables are the temperatures in these regions , eastern tropical Pacific subsurface temperature , and its linkage to western tropical Pacific thermocline changes . Following the original model ( Jin 1998 ; Timmermann et al. 2003 ), the underlying ordinary differential equations describing ENSO and its linkage to

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