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James F. Booth, Lu Anne Thompson, Jérôme Patoux, Kathryn A. Kelly, and Suzanne Dickinson

influences the transient dynamics of the atmosphere. Nakamura et al. (2008) use an AGCM to show that the SST front in the Southern Hemisphere acts to anchor, or fix the location of, the wintertime storm track. They theorize that the turbulent heat fluxes from the ocean to the atmosphere on the warm side of the SST front reinvigorate the low-level atmospheric baroclinicity that is removed by wind advection associated with a passing storm. Nakamura and Yamane (2009) show that anomalies in the monthly

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Masami Nonaka, Hisashi Nakamura, Bunmei Taguchi, Nobumasa Komori, Akira Kuwano-Yoshida, and Koutarou Takaya

observations. J. Geophys. Res. , 108 , 3078 – 3094 . Nakamura , H. , and A. Shimpo , 2004 : Seasonal variations in the Southern Hemisphere storm tracks and jet streams as revealed in a reanalysis dataset. J. Climate , 17 , 1828 – 1844 . Nakamura , H. , T. Sampe , Y. Tanimoto , and A. Shimpo , 2004 : Observed associations among storm tracks, jet streams and midlatitude oceanic fronts. Earth Climate: The Ocean–Atmosphere Interaction, Geophys. Monogr., Vol. 147, Amer. Geophys

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Jianping Li, Zhiwei Wu, Zhihong Jiang, and Jinhai He

the southern flank is primarily controlled by anomalously westerly winds. Such wind anomalies tend to shift the EA subtropical jets more southward than normal. Meanwhile, the WPSH also withdraws southward. Large areas of positive 500-hPa H anomalies occupy the Philippine Sea and SCS, while the East China Sea, Korean Peninsula, and Japan Islands and the adjacent oceans are controlled by negative 500-hPa H anomalies. Coupled with such circulation changes, the subtropical rain belt shifts

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Bunmei Taguchi, Hisashi Nakamura, Masami Nonaka, and Shang-Ping Xie

confirmed the high sensitivity of storm-track activity to the midlatitude SST gradient. However, it has not been fully understood what specific processes are operative in the oceanic baroclinic adjustment. Recently, Nonaka et al. (2009) have scrutinized the processes involved in the maintenance of surface baroclinicity across a prominent oceanic front simulated in a high-resolution coupled GCM. They focused on the Antarctic polar frontal zone (APFZ) in the southern Indian Ocean. The APFZ exhibits

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Kathryn A. Kelly, R. Justin Small, R. M. Samelson, Bo Qiu, Terrence M. Joyce, Young-Oh Kwon, and Meghan F. Cronin

vertical shear of the horizontal wind multiplied by f / N (where f is the Coriolis force). Indeed, Cione et al. (1993) used the horizontal thermal gradient between the air temperature at Cape Hatteras and SST at the GS north wall as a measure of baroclinicity with which to estimate the potential growth of storms passing that way. Nakamura and Shimpo (2004) found that within the core region of the Southern Hemisphere storm track and subpolar jet over the Indian Ocean, the lower-troposphere eddy

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Takeaki Sampe, Hisashi Nakamura, Atsushi Goto, and Wataru Ohfuchi

relaxing by poleward eddy heat fluxes, regardless of the presence of planetary waves. As is well known, the surface westerlies are of great importance in the general circulation of the ocean. For example, they play a major role in driving the ACC ( Gnanadesikan and Hallberg 2000 ) and its changes (e.g., Oke and England 2004 ), which might influence the storage of heat and greenhouse gases in the Southern Ocean ( Russell et al. 2006 ). Therefore, understanding the driving mechanisms of the midlatitude

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Young-Oh Kwon, Michael A. Alexander, Nicholas A. Bond, Claude Frankignoul, Hisashi Nakamura, Bo Qiu, and Lu Anne Thompson

representation (within the grid resolution) of its southern edge and positioning of its extension. The poleward displacement of the northern edge leads to a 1-psu saline bias and 4°C warm bias ( Fig. 14a ): Correspondingly, the local heat loss to the atmosphere is excessive by ~100 W m −2 . An ocean-only simulation (i.e., an ocean model forced by repeated annual forcing from observation; see Thompson and Cheng 2008 for details) gives very similar results, with too warm water upstream and a too cool region

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Lu Anne Thompson and Young-Oh Kwon

1. Introduction Observations of a shift in the climate of the North Pacific Ocean around 1976–77 and the link to large-scale patterns in sea surface temperature (SST; Mantua et al. 1997 ) have lead to a search for potential sources of decadal variability in the ocean–atmosphere system in the North Pacific sector. Observations show two modes of variability in SST in the Pacific Ocean ( Deser and Blackmon 1995 ), the first with a large expression in the tropics and a maximum of a different sign

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Daisuke Hotta and Hisashi Nakamura

filtering. The activity of a transient eddy can be measured as the variance in geopotential height or meridional wind velocity, or as a poleward heat flux based on their filtered time series. In both the Northern and Southern Hemispheres (NH and SH, respectively), distinct maxima of measured eddy activity are observed in longitudinally confined regions above the midlatitude oceans ( Figs. 1a,c ): over the North Atlantic and over the North Pacific ( Blackmon et al. 1977 ; Hoskins and Valdes 1990

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Shoshiro Minobe, Masato Miyashita, Akira Kuwano-Yoshida, Hiroki Tokinaga, and Shang-Ping Xie

and Brazil–Malvinas Currents, interesting oceanic signatures in surface wind were reported, but low SSTs (colder than 20°C even in local summer) probably prevent the deep heating mode from being dominant in the extratropical Southern Hemisphere. The western North Pacific meets both conditions for the deep heating mode. Very recently, Tokinaga et al. (2009) showed deep penetration of upward winds in summer (June–July) over the Kuroshio Extension, accompanied by frequent cloud-top occurrence at

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