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  • 1
    Online Resource
    Online Resource
    Wave, Vortex and Wave‐Vortex Dipole (Instability Wave): Three Flavors of the Intra‐Seasonal Variability of the North Equatorial Undercurrent
    American Geophysical Union (AGU) ; 2022
    In:  Geophysical Research Letters Vol. 49, No. 11 ( 2022-06-16)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 49, No. 11 ( 2022-06-16)
    Abstract: Three flavors of the sub‐thermocline variability—wave, vortex (mesoscale eddy) and wave‐vortex dipole (WVD)—of the North Equatorial Undercurrent are identified The WVD consists of a pair of antisymmetric vortices and is characterized by lens‐like temperature anomalies The WVD is identified as a second baroclinic mode‐like Rossby wave‐initiated instability wave fueled by baroclinic conversion
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2021GL097239
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Image_5.tiff
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-6-9)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-6-9)
    Abstract: The maintenance and variation of the Pacific Equatorial Undercurrent (EUC) are thought to be controlled by the zonal pressure gradient force (ZPGF). However, a recent study found that a large-scale circulation associated with Rossby waves can also lead to EUC variation, implying that the structures and timing of the influential winds and the underlying wind-driven mechanisms need to be revisited. Here, we use the adjoint-sensitivity method to obtain the crucial winds that can most efficiently influence EUC variations. The obtained adjoint sensitivities (denoting the sensitive winds) are confined to 15°S–15°N and exhibit a funnel-shaped pattern with high symmetry about the equator. The remote winds, which occur 4 to 11 months prior, can lead to EUC variations at the basin scale; in contrast, the near-term winds (occurring not earlier than 4 months) lead only to local EUC variations. Accordingly, we find that wind-initiated equatorial Kelvin waves, equatorial Rossby waves, and the reflected waves at both the western and eastern boundaries superimpose onto each other to result in EUC variations. Specifically, when the travel time is longer than 4 months, the waves can form a negative-positive-negative sea surface height anomaly (SSHA) pattern between 15°S and 15°N in the central-eastern tropical Pacific, indicating the joint effect of both types of waves; they also form a positive SSHA in the western equatorial Pacific, indicating the dominance of the Kelvin wave therein. These mechanisms are complementary to the canonical ZPGF mechanism, which provide a clear theoretical basis for EUC variation studies.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2022.908939
    DOI: 10.3389/fmars.2022.908939.s001
    DOI: 10.3389/fmars.2022.908939.s002
    DOI: 10.3389/fmars.2022.908939.s003
    DOI: 10.3389/fmars.2022.908939.s004
    DOI: 10.3389/fmars.2022.908939.s005
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2757748-X
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  • 3
    Online Resource
    Online Resource
    The Adjoint-Based Favorable Winds for the Generation of the Central Pacific El Niño
    American Meteorological Society ; 2023
    In:  Journal of Climate Vol. 36, No. 16 ( 2023-08-15), p. 5491-5510
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 36, No. 16 ( 2023-08-15), p. 5491-5510
    Abstract: Central Pacific (CP) El Niño (i.e., CP El Niño) events have occurred more frequently during recent decades. Wind stress patterns are argued to have significant effects on the generation and evolution of CP El Niño. However, the winds differ in different CP El Niño events, making it hard in previous studies to avoid overgeneralizing the timing and location of the winds that indeed matter. In this study, the theoretically favorable wind perturbations (FWPs) that may warm the Niño-4 region, in terms of their directions, horizontal structures, and bounds, in each month before the peak month (December) of CP El Niños are determined, using an adjoint sensitivity method. The mechanisms of the FWPs are interpreted. Primarily, zonal temperature advection via the equatorial wave–associated velocity anomalies is responsible. In particular, easterly FWPs over the central equatorial Pacific with off-equatorial westerly FWPs (constituting a wind structure with a strong north–south gradient) during the first half year can play a positive role in warming the Niño-4 region and so can the westerly FWPs over the western tropical Pacific, while westerly FWPs in the western-central tropical Pacific in the second half year show higher efficiency. Meanwhile, the particular wind structure of the first half year (i.e., the easterly anomaly over the central equatorial Pacific with strong wind stress curl off the equator) has also been verified to be able to produce a CP-type warming in an intermediate coupled model (ICM); similar wind stress anomalies had been observed in some CP El Niño events. Thus, the FWPs provide helpful guidance in analyzing the generation and evolving processes of the wind-driven CP El Niño.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-22-0548.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 4
    Online Resource
    Online Resource
    Deep-reaching thermocline mixing in the equatorial pacific cold tongue
    Springer Science and Business Media LLC ; 2016
    In:  Nature Communications Vol. 7, No. 1 ( 2016-05-12)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2016-05-12)
    Abstract: Vertical mixing is an important factor in determining the temperature, sharpness and depth of the equatorial Pacific thermocline, which are critical to the development of El Ninõ and Southern Oscillation (ENSO). Yet, properties, dynamical causes and large-scale impacts of vertical mixing in the thermocline are much less understood than that nearer the surface. Here, based on Argo float and the Tropical Ocean and Atmosphere (TAO) mooring measurements, we identify a large number of thermocline mixing events occurring down to the lower half of the thermocline and the lower flank of the Equatorial Undercurrent (EUC), in particular in summer to winter. The deep-reaching mixing events occur more often and much deeper during periods with tropical instability waves (TIWs) than those without and under La Niña than under El Niño conditions. We demonstrate that the mixing events are caused by lower Richardson numbers resulting from shear of both TIWs and the EUC.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/ncomms11576
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 2553671-0
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  • 5
    Online Resource
    Online Resource
    The Northeast‐Southwest Oscillating Equatorial Mode of the Tropical Instability Wave and Its Impact on Equatorial Mixing
    American Geophysical Union (AGU) ; 2019
    In:  Geophysical Research Letters Vol. 46, No. 1 ( 2019-01-16), p. 218-225
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 46, No. 1 ( 2019-01-16), p. 218-225
    Abstract: At the equator, zonal velocity oscillations of the 17‐day TIW are identified, in complement to the well‐known meridional oscillations The resulting NE‐SW oscillating, equatorial mode TIW differs from both the Yanai wave at the equator or the TIV north of the equator The westward anomalous velocities induce the strongest vertical shear in the subsurface ocean, favoring the equatorial turbulent mixing
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2018GL080226
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    The Subsurface Mode Tropical Instability Waves in the Equatorial Pacific Ocean and Their Impacts on Shear and Mixing
    American Geophysical Union (AGU) ; 2019
    In:  Geophysical Research Letters Vol. 46, No. 21 ( 2019-11-16), p. 12270-12278
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 46, No. 21 ( 2019-11-16), p. 12270-12278
    Abstract: Subsurface tropical instability waves, with zonal velocity oscillation peaking at 70–90 m, are identified in the eastern equatorial Pacific The waves have periods of 5–20 days and amplitudes of 0.1–0.2 m/s and can persist for 3–7 months from July to the following February The waves can induce periodically enhanced and reduced shear and hence mixing at ~50 m and above the core of the Equatorial Undercurrent
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2019GL085123
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Four Types of Baroclinic Instability Waves in the Global Oceans and the Implications for the Vertical Structure of Mesoscale Eddies
    American Geophysical Union (AGU) ; 2021
    In:  Journal of Geophysical Research: Oceans Vol. 126, No. 3 ( 2021-03)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 126, No. 3 ( 2021-03)
    Abstract: Four vertical types of baroclinic instability (BCI) are identified, and their global distributions are determined The BCI waves’ propagation speeds are controlled by BCI type‐dependent mean flows Subsurface‐intensified BCI waves dominate off‐equatorial regions that correspond to reported hotspots for subsurface eddies
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2020JC016966
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Seasonality of Four Types of Baroclinic Instability in the Global Oceans
    American Geophysical Union (AGU) ; 2022
    In:  Journal of Geophysical Research: Oceans Vol. 127, No. 5 ( 2022-05)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 127, No. 5 ( 2022-05)
    Abstract: Global baroclinic instability (BCI) types show obvious seasonality, particularly in the Kuroshio Extension/Gulf Stream and tropic‐subtropics BCI seasonality in the former regions is controlled by density stratification and in the latter additionally by vertical velocity shear The seasonality of BCIs may lead to seasonal variation of eddy types, confirmed by baroclinic energy conversion rates
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2022JC018572
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    The adjoint-based Two Oceans One Sea State Estimate (TOOSSE)
    Springer Science and Business Media LLC ; 2022
    In:  Journal of Oceanology and Limnology Vol. 40, No. 1 ( 2022-01), p. 1-21
    Details
    In: Journal of Oceanology and Limnology, Springer Science and Business Media LLC, Vol. 40, No. 1 ( 2022-01), p. 1-21
    Type of Medium: Online Resource
    ISSN: 2096-5508 , 2523-3521
    URL: Article
    DOI: 10.1007/s00343-021-0439-9
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2931064-7
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  • 10
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    Online Resource
    On the Formation of a Subsurface Weakly Sheared Laminar Layer and an Upper Thermocline Strongly Sheared Turbulent Layer in the Eastern Equatorial Pacific: Interplays of Multiple-Time-Scale Equatorial Waves
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 10 ( 2020-10-01), p. 2907-2930
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 10 ( 2020-10-01), p. 2907-2930
    Abstract: The origins of an observed weakly sheared nonturbulent (laminar) layer (WSL), and a strongly sheared turbulent layer above the Equatorial Undercurrent core (UCL) in the eastern equatorial Pacific are studied, based mainly on the data from the Tropical Atmosphere and Ocean mooring array. Multiple-time-scale (from 3 to 25 days) equatorial waves were manifested primarily as zonal velocity oscillations with the maximum amplitudes (from 10 to 30 cm s −1 ) occurring at different depths (from the surface to 85-m depths) above the seasonal thermocline. The subsurface-intensified waves led to vertically out-of-phase shear variations in the upper thermocline via destructive interference with the seasonal zonal flow, opposing the tendency for shear instability. These waves were also associated with depth-dependent, multiple-vertical-scale stratification variations, with phase lags of π /2 or π , further altering stability of the zonal current system to vertical shear. The WSL and UCL were consequently formed by coupling of multiple equatorial waves with differing phases, particularly of the previously identified equatorial mode and subsurface mode tropical instability waves (with central period of 17 and 20 days, respectively, in this study), and subsurface-intensified waves with central periods of 6, 5, and 12 days and velocity maxima at 45-, 87-, and 40-m depths, respectively. In addition, a wave-like feature with periods of 50–90 days enhanced the shear throughout the entire UCL. WSLs and UCLs seem to emerge without a preference for particular tropical instability wave phases. The generation mechanisms of the equatorial waves and their joint impacts on thermocline mixing remain to be elucidated.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-19-0245.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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