Search Results

You are looking at 1 - 10 of 20 items for :

  • CLIVAR - Western Boundary Currents x
  • All content x
Clear All
Takeaki Sampe, Hisashi Nakamura, Atsushi Goto, and Wataru Ohfuchi

1. Introduction Synoptic-scale transient eddies are one of the essential components of the tropospheric general circulation, because they transport a substantial amount of heat, moisture, and angular momentum meridionally. The momentum transport maintains midlatitude westerlies, which can be organized as an eddy-driven jet, called a “polar front jet” (“PFJ”; also called a subpolar jet; Palmén and Newton 1969 ). The eddy activity reaches a maximum over the midlatitude oceans where it forms

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

drives such a change of the EASM. Figure 4 presents the composite difference of 200-hPa JJA winds and 500-hPa geopotential heights H between the 1958–79 and 1980–2008 periods over EA (the latter minus the former). A noticeable feature is that large areas of positive H anomalies associated with anticyclonic wind anomalies prevail over northern EA. The northern flank of climatological westerly jets over EA (color shadings in Fig. 4 ) is basically controlled by anomalously easterly winds, whereas

Full access
Mototaka Nakamura and Shozo Yamane

the eddy fields’ maxima to be displaced southward and downstream in cold months. In the summer, however, they are displaced slightly to the north of the OE. The upper-tropospheric storm track core marked by the maximum V  ′ V  ′ is located downstream of the jet core marked by the U maximum throughout the year, with the displacement during cold months being much greater than that in the summer. The difference is attributed to the difference in the strength of the upper-tropospheric flow that

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

, Nakamura et al. (2004) proposed a new framework for interpreting how the mean state of the tropospheric general circulation is maintained, in which midlatitude oceanic fronts play a significant role in anchoring storm tracks and their associated westerly polar-front jets. They argued that the differential heat supply from the ocean to the atmosphere across a midlatitude oceanic frontal zone acts to maintain the surface baroclinicity, which is necessary for the recurrent development of cyclones and

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

with the current ( Fig. 4 , top panel) reveal that spatial variations in the air–sea temperature difference are nearly as large as the synoptic variations. Turbulent heat fluxes as large as 1000 W m −2 were measured over the GS using the direct covariance method during the CLIMODE field program in 2007 ( The CLIMODE Group 2009 ), while mooring observations just north of the KE jet show mean values of more than 600 W m −2 during wintertime northerly wind events ( Konda et al. 2010 ). The cold

Full access
Daisuke Hotta and Hisashi Nakamura

Extension [the subarctic frontal zone (SAFZ)] acts to anchor the storm track along it, while the strong subtropical jet acts to trap upper-level synoptic eddies into its core and thereby retard their efficient coupling with the surface baroclinic zone. Nakamura and Shimpo (2004) found that a surface baroclinic zone anchored by the distinct SST frontal zone between the Antarctic Circumpolar Current (ACC) and the Agulhas Current in the south Indian Ocean [Antarctic polar frontal zone (APFZ)] coincides

Full access
Claude Frankignoul, Nathalie Sennéchael, Young-Oh Kwon, and Michael A. Alexander

significant changes in the year-to-year near-surface synoptic activity. Observational attempts to relate large-scale tropospheric fluctuations in the North Atlantic sector to prior changes of the Gulf Stream have failed ( Frankignoul et al. 2001 ), but the atmospheric circulation in the North Pacific sector appears to be influenced by SST anomalies in the KE region ( FS07 ; Qiu et al. 2007 ). However, lacking a reliable indicator of the KE jet changes, the signals could not be firmly linked to the

Full access
Masanori Konda, Hiroshi Ichikawa, Hiroyuki Tomita, and Meghan F. Cronin

1. Introduction The Kuroshio and the Kuroshio Extension (KE) contribute to the meridional heat transport system in the Pacific Ocean. Persistent warm surface water in the KE region is considered to be one of the main reasons for the large heat release in fall and winter (e.g., Deser et al. 1999 ; Qiu et al. 2004 ). Thus, the strong sea surface temperature (SST) front associated with the KE jet naturally divides the KE region into two subregions. South of the front, a recirculation gyre is

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

by SST changes are different from one model to another ( Kushnir et al. 2002 ). Also, even within the same model, the atmospheric response to given SST anomalies can be different with different background states (e.g., Peng et al. 1997 ). A recent study suggests that the different responses can be understood in terms of changes in the position of the midlatitude SST front relative to the subtropical jet ( Brayshaw et al. 2008 ). The Gulf Stream is the strongest western boundary current ( Tomczak

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

and polar-front jet (PFJ; or subpolar jet) that accompanies it. An idealized AGCM experiment by Brayshaw et al. (2008) with zonally symmetric SST distribution showed high sensitivity of the position and intensity of a midlatitude storm track to the meridional SST profile and the strength of a subtropical jet (STJ). Another idealized AGCM experiment by Nakamura et al. (2008) with zonally symmetric SST showed that a midlatitude frontal SST gradient anchors a storm track by energizing migratory

Full access