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Lisan Yu, Xiangze Jin, and Robert A. Weller

1. Introduction The Indian Ocean is the only ocean that is bounded by land at the tropical latitudes around 26°N. On the climatological annual-mean basis, ship-based flux products indicate that there is net heat going into the ocean north of 15°S ( Hastenrath and Lamb 1979a , b ; Esbensen and Kushnir 1981 ; Hsiung 1985 ; Oberhuber 1988 ; da Silva et al. 1994 ; Josey et al. 1999 ). Of the heat stored by the ocean, part is released to the atmosphere, mostly by latent evaporation and

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Clémentde Boyer Montégut, Jérôme Vialard, S. S. C. Shenoi, D. Shankar, Fabien Durand, Christian Ethé, and Gurvan Madec

importance of upper-ocean stratification, caused by the freshwater fluxes, for the thermodynamics of the upper ocean. The stratification due to salinity leads to the existence of a barrier layer similar to that in the western tropical Pacific (see, e.g., Vialard and Delecluse 1998 ). Sengupta et al. (2002) highlighted the importance of penetrative solar radiation in determining the upper-layer heat budget of the eastern AS. Both the barrier layer, which often leads to subsurface inversions ( Shankar

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Rui-Jin Hu and J. Stuart Godfrey

1. Introduction In the previous paper ( Godfrey et al. 2007 , hereafter Part I ) it was shown that observed annual mean net heat fluxes (AMNHFs) into the tropical Indian Ocean are much greater than those from present-day ocean general circulation models (OGCMs); see Fig. 1 . This suggests that this region of the ocean may couple more strongly with the atmosphere than previously thought, with consequences for (e.g.) predictability of monsoons, or ENSO. It also means that, in the real Indian

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

1. Introduction This paper and the following one ( Hu and Godfrey 2007 , hereafter Part II ) suggest that ocean general circulation models (OGCMs) are systematically underestimating the annual mean net heat flux (AMNHF) into the northern Indian Ocean, and explore possible reasons for this. The magnitude of interannual variation of any quantity is often roughly proportional to its mean. If the AMNHF into this region is underestimated, its interannual variability—and hence the amount of heat

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Jean Philippe Duvel and Jérôme Vialard

). These perturbations are associated with westerly wind bursts generating important surface flux perturbations (e.g., Weller and Anderson 1996 ; Duvel et al. 2004 ). Many studies suggest that these westerly wind bursts can also play an important role in the onset of El Niño events when they have significant amplitude along the equator in the western Pacific Ocean (e.g., McPhaden 1999 ; Lengaigne et al. 2002 ). The mechanisms for the generation and the evolution of the intraseasonal variability of

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

the western Pacific. Lau and Nath (2003) and Shinoda et al. (2004a) also showed that SST variations in the central and eastern Pacific are capable of producing realistic El Niño–related zonal wind variations and surface heat flux anomalies over the eastern tropical Indian Ocean, through one-dimensional mixed layer processes. These surface heat flux anomalies capture the cooling of the eastern Indian Ocean during boreal summer and fall, followed by a rapid warming in boreal winter, resulting in

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J. C. Hermes, C. J. C. Reason, and J. R. E. Lutjeharms

Current is in fact enhanced by a further 30 Sv from this recirculation subgyre, implying that of the three sources it contributes the most volume flux to the Agulhas Current. It is also possible that the recirculation may be influenced by seasonal shifts of the south Indian Ocean anticyclone ( Preston-Whyte and Tyson 1988 ). Since the recirculation seems to be the major contributor to the Agulhas Current it is conceivable that a seasonal variability to the inflow to the Agulhas Current may occur. The

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Bohua Huang and J. Shukla

interannual variability in the tropical Indian Ocean. Previous studies have emphasized the effects of the surface heat flux over the tropical Indian Ocean (e.g., Klein et al. 1999 ; Venzke et al. 2000 ; Lau and Nath 2000 , 2003 ; Baquero-Bernal et al. 2002 ; Li et al. 2003 ; Yu and Lau 2004 ). In this study, we further examine the role of the ocean dynamics in the tropical air–sea feedback. We also distinguish the tropical air–sea interaction from those in the subtropical Indian Ocean where the

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

Atmosphere Sea Ice Soil (OASIS 2.4; Valcke et al. 2000 ) coupling software package. No measures for flux adjustments are taken in the model. For the AGCM, a semi-Lagrangian transport method ( Rasch and Williamson 1990 ) is used for the advection of cloud water and water vapor, while the parameterization of Tiedtke (1989) is used to represent convection and that of Morcrette (1991) is used for radiation. The horizontal resolution of the OGCM is 2° × 2° cosine (latitude) with an increased meridional

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Tommy G. Jensen

wind patterns and SST during IOD events in El Niño years and during non–El Niño years, and provides a detailed discussion of the role of advection and heat flux. The two following papers address the response of the Indian Ocean. Using an Indian Ocean model driven with composite winds, Jensen finds that the annual clockwise cross-equatorial circulation of the upper Indian Ocean on average is slowed down during La Niña years, allowing Bay of Bengal water to enter the Arabian Sea. Conversely, the

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