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Mototaka Nakamura and Shozo Yamane

of the storm track entrance, as one may anticipate from the geostrophic balance as the valid first approximation to the planetary- and synoptic-scale atmospheric motions. There is a general positive correlation between B x and U in the troposphere and lower stratosphere. However, the anomalous thermal wind associated with the horizontal temperature gradient anomalies in the lowest part of the atmosphere alone does not explain all of the U anomalies in the upper troposphere and stratosphere

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Daisuke Hotta and Hisashi Nakamura

fluxes, surface westerlies are maintained along midlatitude storm tracks; (b) The induced westerlies reinforce the warm WBC; (c) from which moisture supply to the atmosphere is enhanced; (d) Then latent heat release associated with precipitating storms is also enhanced; (e) inducing a steady planetary wave response in which mean baroclinicity along the storm track and the surface westerlies over the ocean basin are reinforced; and (f) the enhanced mean baroclinicity, in turn, maintains the storm

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Akira Kuwano-Yoshida, Shoshiro Minobe, and Shang-Ping Xie

temperature in the northwestern Atlantic. Mon. Wea. Rev. , 129 , 1273 – 1294 . Gyakum , J. R. , and P. J. Roebber , 2001 : The 1998 ice storm—Analysis of a planetary-scale event. Mon. Wea. Rev. , 129 , 2983 – 2997 . Hogg , A. M. , W. K. Dewar , P. Berloff , S. Kravtsov , and D. K. Hutchinson , 2009 : The effects of mesoscale ocean–atmosphere coupling on the large-scale ocean circulation. J. Climate , 22 , 4066 – 4082 . Hoskins , B. J. , and P. J. Valdes , 1990 : On

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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

1. Introduction In the strong Northern Hemisphere midlatitude western boundary current (WBC) systems—the Gulf Stream (GS) in the North Atlantic and the Kuroshio Extension (KE) in the North Pacific—there is a complex interaction between dynamics and thermodynamics and between the atmosphere and ocean ( Fig. 1 ). A precipitous drop in the meridional transport of heat in the Northern Hemisphere ocean occurs where these warm WBCs separate from the coast and flow into the ocean interior ( Trenberth

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

the oceanic western boundary currents is important for strong diabatic heating in storm-track regions, which excites planetary waves that enhance baroclinicity around the storm-track regions. Nakamura et al. (2004 , 2008) argued that, because of the large heat capacity of the oceanic mixed layer and the strong thermal advection by confluent ocean currents, the presence of an oceanic front can exert a strong restoring effect on baroclinicity of the overlying atmosphere that is subject to

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

the deep ocean ML and the maintenance of the fronts by oceanic advection. The large heat and moisture fluxes to the south of the WBCs can enhance latent heating associated with cyclones, thereby acting to organize precipitation bands and the associated heat source regions for atmospheric planetary waves ( Hoskins and Valdes 1990 ; Minobe et al. 2008 ). Over most of the midlatitude oceans Q net variability is controlled largely by the atmosphere ( Cayan 1992 ; Frankignoul and Kestenare 2002

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Xujing Jia Davis, Lewis M. Rothstein, William K. Dewar, and Dimitris Menemenlis

1. Introduction Mode waters are waters with exceptionally uniform properties over an extended depth range. Regions of mode water formation are of particular interest to climate since these are areas where atmospheric variability is transmitted to large volumes of water that penetrate and are sequestered below the surface layer. Mode waters integrate the atmosphere’s influence on the ocean and therefore provide a link between the shorter time scales of the atmosphere and the longer time scales

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

evidence is emerging that the midlatitude atmosphere does respond to fine structures of SST associated with oceanic fronts and eddies ( Nonaka and Xie 2003 ; Chelton et al. 2004 ; Xie 2004 ; Tokinaga et al. 2006 ; Small et al. 2008 ), but the response is localized and mostly confined to the atmospheric planetary boundary layer (PBL). Climatologically, a western boundary current associated with a subtropical gyre transports a huge amount of heat from the tropics into a midlatitude oceanic frontal

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

overlying atmosphere is still under debate. Summarizing the results of numerical experiments carried out previously with atmospheric general circulation models (GCMs), Kushnir et al. (2002) concluded that no coherent large-scale atmospheric response had been obtained to prescribed midlatitude sea surface temperature (SST) anomalies. Rather, midlatitude SST anomalies in general have been shown to be forced primarily by atmospheric anomalies ( Frankignoul 1985 ) through changes in surface heat fluxes

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Nicholas A. Bond, Meghan F. Cronin, and Matthew Garvert

et al. 2006 ; Minobe et al. 2008 ; Tokinaga et al. 2009 ), the extent to which the larger-scale atmospheric circulation is sensitive to anomalies in SST is controversial (e.g., Kushnir et al. 2002 ). There is tentative evidence that this sensitivity is mediated by the atmosphere’s basic state (e.g., Peng et al. 1997 ; Bond and Harrison 2000 ). It is plausible to suppose that extratropical transitions are particularly sensitive to SST, because of the latter’s impact on the surface fluxes of

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