The Baroclinic Response of the West Tropical Pacific to Wind Stress

Wang

Shi-Kuo

et al. 2005

Chinese J. Geophys.

The synchronous response of tropical ocean to meridional and zonal wind stress has been studied. The results show that meridional wind stress of the first order that diverges or converges affects the velocity and geopotential fields. The disturbed termocline and the zonal flow of the zeroth order are driven directly by wind stress and affected by Kelvin wave and short Rossby wave. Rossby wave is produced by meridional wind stress. The disturbed termocline and the zonal flow of the second order mode are driven directly by wind stress and affected by short Rossby wave. At the same time, the meridional wind stress also produces the short Rossby wave. In addition, warm water is recruited to equator district strongly at the west boundary, which indicates that the meridional wind stress may transport the warm water equatorward, and the westerly wind stress transports the warm water at the west boundary eastward.

Section: The Laplace Transform Inversion For Solutionsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Synchronous Response of Tropical Ocean to Meridional and Zonal Wind Stress

Wang

Shi-Kuo

et al. 2005

Chinese J. Geophys.

“…Afterwards, utilizing the coupled ocean-atmosphere model (CGCM), Yu and Mechoso [28] simulated successfully the coupling process during the ENSO cycle, and confirmed the observed results mentioned above. In recent years, Chao et al [29,30] and Li [31] analyzed the propagation of the subsurface layer ocean temperature anomalies in the tropical Pacific and discovered that the anomalous ocean temperature signals forming ENSO events propagated eastward along the equator at the thermocline depth from the West Pacific to the East Pacific and then propagated away from the equator, at the same time there existed a anomalous ocean temperature signal with opposite signs propagating westward along the latitudes of 10°S and 10°N respectively and then turn towards the equator to form two complete cycles. The above results reveal a new evolving process for El Niño/La Niña events, providing a factual basis for further understanding the mechanism of the ENSO cycle.…”

Section: Introductionmentioning

confidence: 99%

Mixed-layer water oscillations in tropical Pacific for ENSO cycle

Zhao

Sci. China Ser. D-Earth Sci.

Wang

et al. 2007

The main modes of interannal variabilities of thermocline and sea surface wind stress in the tropical Pacific and their interactions are investigated, which show the following results. (1) The thermocline anomalies in the tropical Pacific have a zonal dipole pattern with 160°W as its axis and a meridional seesaw pattern with 6-8°N as its transverse axis. The meridional oscillation has a phase lag of about 90° to the zonal oscillation, both oscillations get together to form the El Niño/La Niña cycle, which behaves as a mixed layer water oscillates anticlockwise within the tropical Pacific basin between equator and 12°N. (2) There are two main patterns of wind stress anomalies in the tropical Pacific, of which the first component caused by trade wind anomaly is characterized by the zonal wind stress anomalies and its corresponding divergences field in the equatorial Pacific, and the abnormal cross-equatorial flow wind stress and its corresponding divergence field, which has a sign opposite to that of the equatorial region, in the off-equator of the tropical North Pacific, and the second component represents the wind stress anomalies and corresponding divergences caused by the ITCZ anomaly. (3) The trade winds anomaly plays a decisive role in the strength and phase transition of the ENSO cycle, which results in the sea level tilting, provides an initial potential energy to the mixed layer water oscillation, and causes the opposite thermocline displacement between the west side and east side of the equator and also between the equator and 12°N of the North Pacific basin, therefore determines the amplitude and route for ENSO cycle. The ITCZ anomaly has some effects on the phase transition. (4) The thermal anomaly of the tropical western Pacific causes the wind stress anomaly and extends eastward along the equator accompanied with the mixed layer water oscillation in the equatorial Pacific, which causes the trade winds anomaly and produces the anomalous wind stress and the corresponding divergence in favor to conduce the oscillation, which in turn intensifies the oscillation. The coupled system of ocean-atmosphere interactions and the inertia gravity of the mixed layer water oscillation provide together a phase-switching mechanism and interannual memory for the ENSO cycle. In conclusion, the ENSO cycle essentially is an inertial oscillation of the mixed layer water induced by both the trade winds anomaly and the coupled ocean-atmosphere interaction in the tropical Pacific basin between the equator and 12°N. When the force produced by the coupled ocean-atmosphere interaction is larger than or equal to the resistance caused by the mixed layer water oscillation, the oscillation will be stronger or maintain as it is, while when the force is less than the resistance, the oscillation will be weaker, even break.tropical Pacific, thermocline and sea surface wind stress anomaly, ENSO cycle, mixed layer water oscillation

“…During the period between the end of the El Nino event and the onset of the La Nina event, the sub-surface abnormal warm water in the northern equatorial current area (in the vicinity of 10°N) spreads from the Middle East Pacific to the western Pacific warm pool subduct along with the thermocline, and the abnormal warm water signal continually increases and extends, and finally the warm water controls the whole western Pacific, and provides the essential conditions for the onset of an El Nino event [2] . Results of Chao et al (2002) showed that the initial ocean temperature departure of El Nino or La Nino aroused by the observation mainly appeared in the thermocline at about 150 m in a warm pool; when its intensity reached up to a specific threshold, it would spread to the tropic western Pacific along with climatic thermocline and move up to the sea surface. In the western boundary of the Pacific, the abnormally forced by the atmosphere can arouse sub-surface temperature anomaly, which spreads to the ocean east, mainly with an eastspread Kelvin wave, and arouses the anomaly in the whole ocean [3] .…”

mentioning

confidence: 98%

Features of the Three Dimensional Structure in the Pacific Sub-surface Layer in Summer

Cheng

Zhang

et al. 2020

j. of atmos. sci. res.

The anomaly of the summer sea temperature is analyzed by a spatial-temporal synthetically rotated orthogonal function (REOF) at three different depths (0 m, 40 m, and 120 m) over the area 110°E~100°W and 30°S~60°N. The spatial-temporal distribution shows that the “signal” of annual anomaly is stronger in the sub-surface layer than the surface layer, and it is stronger in the eastern equatorial Pacific than in the western area. The spatial structure of the sea temperature anomaly at different layers is related to both the ocean current and the interaction of ocean and atmosphere. The temporal changing trend of the sub-surface sea temperature in different areas shows that the annual mean sea temperature increases and the annual variability evidently increases from the 1980s, and these keep the same trend with the increasing El Nino phenomenon very well.