Circulation in the South China Sea is in a state of forced oscillation: Results from a simple reduced gravity model with a closed boundary

Ruixin Huang Hui Zhou

Ruixin Huang, Hui Zhou. Circulation in the South China Sea is in a state of forced oscillation: Results from a simple reduced gravity model with a closed boundary[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-022-2013-5
Citation: Ruixin Huang, Hui Zhou. Circulation in the South China Sea is in a state of forced oscillation: Results from a simple reduced gravity model with a closed boundary[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-022-2013-5

doi: 10.1007/s13131-022-2013-5

Circulation in the South China Sea is in a state of forced oscillation: Results from a simple reduced gravity model with a closed boundary

Funds: The Strategic Priority Research Program of the Chinese Academy of Sciences under contract No. XDB42000000; the National Natural Science Foundation of China under contract No. 41876009.
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  • Figure  1.  Idealized monthly mean wind stress for the model. a. Zonal wind (independent of longitude); b. meridional wind (independent of latitude); based on Global Ocean Data Assimilation System data.

    Figure  2.  The time-latitude diagram of the climatological monthly mean Ekman pumping rate for the model forced by the zonally mean zonal wind stress only (a); the annual mean (b); the basin mean Ekman pumping rate (c).

    Figure  3.  Layer depth in January (a-c) and July(d-f) for the simple model forced by zonally mean zonal wind (a , d, Exp. 1)), by zonally mean zonal wind and meridionally mean meridional wind (b , e , Exp. 2)) and 2D wind (c , f , Exp. 3).

    Figure  4.  Western boundary current transport (a-c) and eastern boundary current (d-f) for a simple model forced by zonally mean zonal wind (a ,d , Exp. 1)), by zonally mean zonal wind and meridionally mean meridional wind (b, e, Exp. 2)) and 2D (c, f, Exp. 3). The margent curves indicate the zero contours (1 Sv=1×106 m3/s).

    Figure  5.  Rossby wave speed (a-c) and the cross- basin time (d-f) for the model located between 0–16°N (Exp. 4, a, d); the model located between 6°–22°N (Exp. 1, b,e) and the model located between 16°–32°N (Exp. 5, c,f).

    Figure  6.  Time evolution of layer depth for the model forced by zonal wind stress only (Exp. 1). The red lines indicate the corresponding signal speed.

    Figure  7.  Volumetric transport of the western boundary current (a-c) and eastern boundary current (d-f). Left column for the model located between 0°–16°N (Exp. 4); middle column for the model located between 6°–22°N (Exp. 1); right column for the model located between 16°–32°N (Exp. 5). The margent curves indicate the zero contours (1 Sv=1×106 m3/s).

    Figure  8.  Experiments forced by idealized monthly zonal/meridional wind (Exp. 2). a. Total volumetric anomaly at each latitude band; b. zonally integrated monthly mean meridional volumetric flux (1 Sv=1×106 m3/s).

    Figure  9.  Experiments forced by idealized monthly zonal/meridional wind (Exp. 2). a. Total volumetric anomaly at each longitude band; b. meridionally integrated monthly mean zonal volumetric flux (1 Sv=1×106 m3/s).

    Figure  10.  Annual cycle of mechanic energy balance. a. For the model forced by zonal wind stress only (Exp. 1); b. for the model forced by two-dimensional zonal/meridional wind (Exp. 3).

    Figure  11.  Vorticity balance for the model forced by zonal wind stress only (Exp. 1).

    Figure  12.  Rossby wave speed (a) and the cross-basin time (b) for the models with the same meridional location, but different zonal width (Exps 1, 6, 7).

    Figure  13.  Latitudinal distribution of volume transport based on models with the same meridional range of 6°–22°N, but different zonal width of 10° (Exp. 1, a, d), 60° (Exp. 6, b, e), and 480° (Exp. 7, c, f) for western boundary current (a-c) and eastern boundary current (d-f) (1 Sv=1×106 m3/s).

    Figure  14.  Time-latitude diagram of volumetric transport of the western boundary current (a-c) and eastern boundary current (d-f) for models with the same meridional range of 6°–22°N , but different zonal width of 10° (Exp. 1, a, d), 60° (Exp. 6, b, e), and 480° (Exp. 7, c, f). The margent curves indicate the zero contours (1 Sv=1×106 m3/s).

    Table  1.   Idealized wind stress data used in the model experiments

    Monthly wind stressZonally mean zonal wind stressZonally mean zonal wind stress and meridionally mean meridional wind stressTwo-dimensional wind stress
    Expression, m=(1, …, 12) is the month$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $,$ {\overline {{\tau ^y}\left( {x,m} \right)} ^y} $${ {\tau ^x}\left( {x,y,m} \right),{\tau ^y}\left( {x,y,m} \right)}$
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    Table  2.   Experiment design

    ExperimentsMeridional rangeZonal rangeWind stressRun duration/a
    Exp. 16°–22°N110°–120°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $20
    Exp. 26°–22°N110°–120°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $,$ {\overline {{\tau ^y}\left( {x,m} \right)} ^y} $20
    Exp. 36°–22°N110°–120°E${ {\tau ^x}\left( {x,y,m} \right),{\tau ^y}\left( {x,y,m} \right)}$20
    Exp. 40°–16°N110°–120°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $20
    Exp. 516°–32°N110°–120°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $40
    Exp. 66°–22°N110°–170°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $60
    Exp. 76°–22°N110°–590°E$ {\overline {{\tau ^x}\left( {y,m} \right)} ^x} $400
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    Table  3.   Volumetric transport of the western/eastern boundary current (WBC/EBC) for three geographic settings of the model ocean

    Transport Western boundary transportEastern boundary transport
    ExperimentExp. 1Exp. 4Exp. 5Exp. 1Exp. 4Exp. 5
    Basin location6°–22°N0°–16°N16°–32°N6°–22°N0°–16°N16°–32°N
    Maximum/Sv2.782.981.690.540.620.55
    Minimum/Sv−4.35−4.22−4.44−0.64−0.57−0.73
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出版历程
  • 收稿日期:  2021-06-10
  • 录用日期:  2021-11-26
  • 网络出版日期:  2022-04-29

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