Search Results

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

  • CLIVAR - Western Boundary Currents x
  • All content x
Clear All
Hailan Wang, Siegfried Schubert, Max Suarez, and Randal Koster

a useful framework for isolating and assessing the roles of the leading SST patterns of variability in forcing U.S. hydroclimate variations (e.g., Schubert et al. 2004a ; Wang et al. 2009 ). However, the exact physical mechanisms by which the leading patterns of SST variability affect the U.S. hydroclimate in the GCMs, and the issue of model dependence of the results has not been sufficiently addressed. A systematic investigation of these mechanisms in AGCM experiments is necessary to improve

Full access
Haiming Xu, Hiroki Tokinaga, and Shang-Ping Xie

midlatitudes, such as the Kuroshio Extension ( Nonaka and Xie 2003 ), Gulf Stream ( Chelton et al. 2004 ), Agulhas Return Current ( O’Neill et al. 2003 ), and Brazil–Malvinas confluence in the South Atlantic ( Tokinaga et al. 2005 ). This positive correlation between SST and wind speed prevails for ocean fronts ( Xie 2004 ; Small et al. 2008 ), in sharp contrast with the negative correlation often observed on the basin scale in the extratropics that is indicative of atmosphere-to-ocean forcing ( Namias

Full access
Daisuke Hotta and Hisashi Nakamura

mechanism of atmospheric baroclinicity (e.g., Stone 1978 ); however, it cannot explain the existence of such meridionally narrow baroclinic zones, as observed near the surface along the storm tracks. HV90 was the first to address this issue. Using a planetary wave model linearized about the observed wintertime zonal-mean flow with each of the transient eddy momentum and heat fluxes and diabatic heating imposed in the NH storm-track regions—namely, the North Atlantic and the North Pacific—as forcing

Full access
Terrence M. Joyce, Young-Oh Kwon, and Lisan Yu

particularly identify the dynamical cause. Because the system is coupled, there are processes within the atmosphere and the ocean separately that will force an alignment between the two ( Hoskins and Valdes 1990 , Nakamura et al. 2008 ): storms can produce vorticity fluxes that enhance the midlatitude zonal jet, which can affect the location of the GS and KE, and then further influence the development of the storms. Recently Tanimoto et al. (2003) have examined decadal variability in SST and interannual

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

that the atmosphere forces the ocean, and experiments using atmospheric general circulation models (AGCMs) with specified extratropical sea surface temperature anomalies (SSTAs) generally yield atmospheric anomalies of modest amplitude and variable spatial structure ( Kushnir et al. 2002 ). Given the low-frequency response of WBCs to integrated basinwide atmospheric forcing, the large ocean-to-atmosphere heat fluxes over the WBCs, their proximity to the storm tracks, and the long time scale

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

-warming background. How would the EASM respond to a global-warming forcing? Section 2 describes the datasets, models, and method employed in this study. Section 3 presents the observed warming trend and variations of precipitation and circulations over EA. Section 4 analyzes the observed relationship between EASM and ENSO. To verify further the conclusion derived from the observations, the response of the EASM to global-warming forcing is investigated with the “A1B” stabilization experiments (with an

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

be rather persistent because of SST anomaly reemergence, sustained forcing from the tropics, and low-frequency changes in oceanic heat advection. The extratropical SST variability is large near the strong SST gradients along the oceanic fronts associated with western boundary currents and their extensions (hereafter WBCs), especially at decadal time scales ( Nakamura et al. 1997 ; Nakamura and Kazmin 2003 ; Kwon et al. 2010a ), when the changes in the oceanic circulation are particularly

Full access
Mototaka Nakamura and Shozo Yamane

advects synoptic-scale disturbances as they enter and grow in the storm track. The characteristics of MR z850 , whose divergence out of and convergence into the planetary boundary layer are related to, respectively, acceleration and deceleration of the surface pseudo-westerlies when the horizontal flux convergence is negligible ( Plumb 1986 ), are roughly in accord with those of V  ′ θ ′ 850 , which is a primary component of MR z850 . The sense of the surface momentum forcing by MR z850 along the

Full access
Lu Anne Thompson and Young-Oh Kwon

decadal SST variability. Schneider et al. (2002) , who also examined ECHO-2, concluded that the decadal time scale of the KOE variability results from the integration along Rossby waves trajectories of stochastic atmospheric forcing. They suggest a positive feedback such that anomalies of wind stress curl over the western North Pacific forced locally by KOE anomalies reinforces those anomalies. However, they found no negative feedback that would close the loop to create a true coupled mode of

Full access
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

Full access