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Jean Philippe Duvel and Jérôme Vialard

perturbations in the Indian Ocean. This shallow thermocline makes cold water readily available to cool the surface by vertical mixing or local upwelling; but, on the other hand, it also limits strongly the depth of the mixed layer, making it more responsive to surface forcing. This surface forcing perturbation itself is due to various physical processes that may have different phasing relative to the maximum convective activity. These physical processes are mainly the screening of the solar heat flux by the

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Hae-Kyung Lee Drbohlav, Silvio Gualdi, and Antonio Navarra

Comprehensive Ocean–Atmosphere Data Set (COADS). The atmospheric forcing variables, such as the air and dewpoint temperatures at 2 m, the mean sea level pressure, and winds at 10 m, are taken from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis project ( Kalnay et al. 1996 ) in order to compute the momentum and heat fluxes interactively with the velocity and sea surface temperature ( Rosati and Miyakoda 1988 ). The assimilation scheme, used

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Karumuri Ashok, Hisashi Nakamura, and Toshio Yamagata

series of the meridional velocity and temperature at the 850-hPa level. This flux has been subject to the 8-day low-pass filtering to represent systematic transport of heat by the transient disturbances. In addition, barotropic feedback forcing by synoptic-scale eddies migrating along a storm track has been evaluated as a local tendency in 250-hPa height ( dZ 250 ) that would be induced due solely to 250-hPa anomalous vorticity flux convergence associated with those eddies ( Nakamura et al. 1997

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Tomoki Tozuka, Jing-Jia Luo, Sebastien Masson, and Toshio Yamagata

forcing play an important role? In Fig. 5 , large decadal anomalies in wind anomalies and SSHAs are seen in the subtropical southern Indian Ocean. It appears that those anomalies are involved in the evolution of the decadal variation in the Tropics. Since the first law of thermodynamics is the basic principle in understanding the change in energy of a climate system, we will address the variations of these heat budgets in the next subsection (cf. Boccaletti et al. 2004 ). b. Mechanism of decadal IOD

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J. Stuart Godfrey, Rui-Jin Hu, Andreas Schiller, and R. Fiedler

patterns. Despite these large intermodel differences the climatologies suggest that the AMNHFs from the OGCMs are rather similar, but nearly all of them seriously underestimate the observed net heat flux. In an unpublished work, referred to below as UW, we and others explored long-term mean northward heat transports in a coarse grid global OGCM. In one experiment (UW − Control) the observed seasonality of all atmospheric forcing variables was retained. In the other (UW − 12MRM), the wind stress (only

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Gary Meyers, Peter McIntosh, Lidia Pigot, and Mike Pook

Meyers 2003 ). These studies also show that as with ENSO, the depth of the thermocline is largely forced by remote winds, from both the Indian and the Pacific Oceans ( Wijffels and Meyers 2004 ). Both remote forcing and the local wind are factors in the generation of the SST of the eastern pole ( Feng and Meyers 2003 ), so that cool SST anomalies (i.e., positive IOD) develop when the easterly wind is favorable for upwelling along the coast of Java and the thermocline is shallow due to remote forcing

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Vinu K. Valsala and Motoyoshi Ikeda

the particles. These tracers are zero-buoyant and independent to any of the modeling restorations. Temperature ( T ) and salinity ( S ) are also typical tracers, which can be used to track the watermass by classical T – S analysis ( You and Tomczak 1993 ), while the difficulty is that they adjust to the surface forcing, and hence, lose the signature of their water types. Instead, the passive tracers with zero surface forcing and restoration will keep their signature on their journey, while they

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Annalisa Cherchi, Silvio Gualdi, Swadhin Behera, Jing Jia Luo, Sebastien Masson, Toshio Yamagata, and Antonio Navarra

consequence of a local effect independent from the forcing from the TPO. Differences are evident while analyzing the behavior in the coupled model; in particular, there is not a clear distinction between the forced and the free SST variability. In both cases, a strong dipolelike dynamics dominates in the tropical Indian Ocean, and the reasons may be ascribed to the simpler dynamics represented in the coupled model with respect to the real world and to the systematic errors of the model already mentioned

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Qian Song, Gabriel A. Vecchi, and Anthony J. Rosati

Niño–Southern Oscillation (ENSO; Bjerknes 1969 ) are not active in the Indian Ocean. Thus, many studies have focused on the interannual Indian Ocean variability resulting from external forcing, in particular that driven by ENSO (e.g., Nigam and Shen 1993 ; Tourre and White 1995 ; Klein et al. 1999 ; Venzke et al. 2000 ; Lau and Nath 2003 ). The ENSO-related SST anomalies (SSTAs) in the Indian Ocean are basin wide and peak about one to two seasons after the maximum of the SSTAs in the central

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Lisan Yu, Xiangze Jin, and Robert A. Weller

measurements ( Fig. 5 ). The first time series was taken from the Arabian Sea Experiment, which took place from October 1994 to October 1995 ( Weller et al. 1998 ). The buoy was located off the coast of Oman at (15.5°N, 61.5°E), a site where some of the strongest winds associated with the southwest monsoon pass through. The experiment was designed to collect measurements of near-surface meteorology and air–sea fluxes that could be used to ascertain the atmospheric forcing under the influence of strong

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