Influence of warm SST anomalies formed in the eastern Pacific subduction zone on recent El Niño events

Anomalous April–June warm surface water in the eastern Pacific convergence zone (the Great Pacific Garbage Patch) subducts and depresses the thermocline as a single waveform. This waveform propagates toward the equator much more quickly (reaching the equator in 1.5–2.5 years) than the normal transit time (5–10 years) of the meridional overturning cell. The movements of the sea-surface temperature (SST) anomalies that occurred before the 1997 and 2009 El Niños can be clearly traced to the area south of 20°N using the altimeter sea-level signals. Upon arriving near the Pacific equator, these warm water anomalies can contribute to the formation of the El Niño by lowering the depth of the thermocline. The time required for a subducted SST anomaly to drift 3000 km to the equator depends upon its initial location and on the distribution of the SST anomalies near the western coast of North America. The subducted warm SST anomalies observed before the El Niños of 1982 and 1997 took 12 months to reach the equator. Longer drift times of 24 months were indicated for the 1972, 1986, 1993, 2003, 2006 and 2009 events. The thermocline depressions that drift toward the equator in the eastern Pacific are shown to be a major energy source for the onset of the El Niño in the central and eastern Pacific. This study presents a theory that could expand our understanding of the onset mechanism of the El Niño episode

Wind-driven secondary circulation in ocean mesoscale

A two-dimensional, numerical circulation model is used to study the response of a stratified, f-plane ocean current to wind stress forcing at the surface. Nonhydrostatic, primitive equations are integrated on a 3 m vertical and 400 m horizontal grid in a periodic domain perpendicular to the ocean current. Initially, a geostrophically balanced current [Vi(x, z)] with a maximum Rossby number of 0.16–0.8 is maintained against horizontal and vertical diffusion by a body force. A spatially uniform wind is applied along and across this jet. A secondary circulation is created as a result of the nonlinear interaction between the jet and wind-driven flow in the Ekman layer. We present results from seven numerical experiments. When the wind blows in the direction of the jet (against the jet), a narrow upwelling (downwelling) area and broad downwelling (upwelling) area are formed. This secondary circulation pattern extends well below the mixed layer. When the wind blows perpendicular to the jet, the secondary circulation does not extend below the mixed layer. The fully nonlinear secondary circulation is 50% weaker than the circulation produced by the semi-linearized calculation around the basic state, Vi. Near-inertial fluctuations appear and are confined to the negative relative vorticity side of the circulation (dV/dx \u3c 0). The time-averaged vertical velocity can be as high as 1.5 m/day with a wind stress of 1 dyne/cm2 over a jet and a maximum Rossby number of 0.16. The magnitude of the vertical circulation in this symmetric basic state is dependent on the Rossby number and the horizontal and vertical mixing coefficients

Evaluando el rendimiento en la tabla de golpeo del makiwara

No hay en la literatura estudios que cuantifiquen las características del impacto en las tablas del makiwara. Lógicamente, la evaluación de las características mecánicas de varios diseños de tablas de makiwara debería ser un paso inicial en la determinación de la validez del makiwara como medio de desarrollo de la técnica del kárate. Consecuentemente, el propósito de este estudio fue determinar la dureza de los diseños del makiwara que se estrecha y en tabla apilada, utilizando técnicas estáticas de carga para evaluar su idoneidad para practicantes de diferentes niveles. Cuando nuestros resultados se observan en términos de progresión del entrenamiento, parece que el diseño apilado de fresno, más flexible, se ajusta mejor al principiante, mientras que el modelo que se estrecha de encina, más rígido, se ajusta mejor al experto

Evaluating Makiwara Punching Board Performance

[ES] No hay en la literatura estudios que cuantifiquen las características del impacto en las tablas del makiwara. Lógicamente, la evaluación de las características mecánicas de varios diseños de tablas de makiwara debería ser un paso inicial en la determinación de la validez del makiwara como medio de desarrollo de la técnica del kárate. Consecuentemente, el propósito de este estudio fue determinar la dureza de los diseños del makiwara que se estrecha y en tabla apilada, utilizando técnicas estáticas de carga para evaluar su idoneidad para practicantes de diferentes niveles. Cuando nuestros resultados se observan en términos de progresión del entrenamiento, parece que el diseño apilado de fresno, más flexible, se ajusta mejor al principiante, mientras que el modelo que se estrecha de encina, más rígido, se ajusta mejor al experto

Low-frequency eddy modulations in the Hawaiian Lee Countercurrent : observations and connection to the Pacific Decadal Oscillation

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): C12009, doi:10.1029/2011JC007286.Interannual-to-decadal time scale eddy variability in the Hawaiian Lee Countercurrent (HLCC) band is investigated using the available sea surface height, sea surface temperature, and surface wind stress data sets. In the HLCC band of 17°N–21.7°N and 170E°–160°W, the prevailing interannual eddy kinetic energy (EKE) signals show enhanced eddy activities in 1993–1998 and 2002–2006, and subpar eddy activities in 1999–2001 and 2007–2009. These interannual EKE signals exhibit little connection to the zonal HLCC velocity changes generated by the dipolar wind stress curl forcing in the immediate lee of the island of Hawaii. Instead, they are highly correlated to the time series of the Pacific Decadal Oscillation (PDO) index. Through a budget analysis for the meridional temperature gradient along the HLCC, we find that during the positive phase of the PDO index, the surface heat flux forcing induces cold (warm) sea surface temperature (SST) anomalies to the north (south) of the HLCC, intensifying the vertical shear between the surface, eastward-flowing HLCC and the subsurface, westward-flowing North Equatorial Current (NEC). This increased vertical shear enhances the baroclinic instability of the HLCC-NEC system and leads to a higher regional EKE level. The opposite processes occur when the PDO switches to a negative phase with the resulting lowered EKE level along the HLCC band. Compared to the surface heat flux forcing, the Ekman flux convergence forcing is found to play a minor role in modifying the meridional SST changes along the HLCC band.We acknowledge support from NOAA through grant NA17RJ1230 for S.Y. and P.H. and NASA’s Ocean Surface topography Mission through JPL contract 1207881 for B.Q.2012-06-0

Observations of the cold wake of Typhoon Fanapi (2010)

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 316–321, doi:10.1029/2012GL054282.Several tens of thousands of temperature profiles are used to investigate the thermal evolution of the cold wake of Typhoon Fanapi, 2010. Typhoon Fanapi formed a cold wake in the Western North Pacific Ocean on 18 September characterized by a mixed layer that was >2.5 °C cooler than the surrounding water, and extending to >80 m, twice as deep as the preexisting mixed layer. The initial cold wake became capped after 4 days as a warm, thin surface layer formed. The thickness of the capped wake, defined as the 26 °C–27 °C layer, decreased, approaching the background thickness of this layer with an e-folding time of 23 days, almost twice the e-folding lifetime of the Sea Surface Temperature (SST) cold wake (12 days). The wake was advected several hundreds of kilometers from the storm track by a preexisting mesoscale eddy. The observations reveal new intricacies of cold wake evolution and demonstrate the challenges of describing the thermal structure of the upper ocean using sea surface information alone.This work is primarily supported by the U.S. Office of Naval Research, with additional support from the National Science Foundation and the National Science Council, Taiwan

Typhoon-ocean interaction in the western North Pacific : Part 1

Author Posting. © The Oceanography Society, 2011. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 24 no. 4 (2011): 24–31, doi:10.5670/oceanog.2011.91.The application of new technologies has allowed oceanographers and meteorologists to study the ocean beneath typhoons in detail. Recent studies in the western Pacific Ocean reveal new insights into the influence of the ocean on typhoon intensity.This work is supported by grants from the Office of Naval Research, N00014- 10-WX-20203 (Black), N00014-08-1- 0656 (Centurioni), N00014-08-1-0577 (D’Asaro), N00014-09-1-0816 (D’Asaro), N00014-10-WX-21335 (Harr), N00014-08-1-0614 (Jayne), N00014- 09-1-0133 (Lee), N00014-08-1-0560 (Lien), N00014-10-1-0313 (student support), N00014-08-1-0658 (Rainville), N00014-08-1-0560 (Sanford); the National Oceanic and Atmospheric Administration NA17RJ1231 (Centurioni); and the National Science Foundation OCE0549887 (D’Asaro)

The Kuroshio Extension northern recirculation gyre : profiling float measurements and forcing mechanism

Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1764-1779, doi:10.1175/2008JPO3921.1.Middepth, time-mean circulation in the western North Pacific Ocean (28°–45°N, 140°–165°E) is investigated using drift information from the profiling floats deployed in the Kuroshio Extension System Study (KESS) and the International Argo programs. A well-defined, cyclonic recirculation gyre (RG) is found to exist north of the Kuroshio Extension jet, confined zonally between the Japan Trench (145°E) and the Shatsky Rise (156°E), and bordered to the north by the subarctic boundary along 40°N. This northern RG, which is simulated favorably in the eddy-resolving OGCM for the Earth Simulator (OFES) hindcast run model, has a maximum volume transport at 26.4 Sv across 159°E and its presence persists on the interannual and longer time scales. An examination of the time-mean x-momentum balance from the OFES hindcast run output reveals that horizontal convergence of Reynolds stresses works to accelerate both the eastward-flowing Kuroshio Extension jet and a westward mean flow north of the meandering jet. The fact that the northern RG is eddy driven is further confirmed by examining the turbulent Sverdrup balance, in which convergent eddy potential vorticity fluxes are found to induce the cyclonic RG across the background potential vorticity gradient field. For the strength of the simulated northern RG, the authors find the eddy dissipation effect to be important as well.This study was supported by NSF through Grant OCE-0220680 (UH) and OCE-0220161 (WHOI)