Observational characteristics and dynamic mechanism of low-salinity water lens for the offshore detachment of the Changjiang River diluted water in August 2006

Zhenyu Liu Wenjing Zhang Xuejun Xiong Shouxian Zhu

Zhenyu Liu, Wenjing Zhang, Xuejun Xiong, Shouxian Zhu. Observational characteristics and dynamic mechanism of low-salinity water lens for the offshore detachment of the Changjiang River diluted water in August 2006[J]. Acta Oceanologica Sinica, 2021, 40(3): 34-45. doi: 10.1007/s13131-021-1710-9
Citation: Zhenyu Liu, Wenjing Zhang, Xuejun Xiong, Shouxian Zhu. Observational characteristics and dynamic mechanism of low-salinity water lens for the offshore detachment of the Changjiang River diluted water in August 2006[J]. Acta Oceanologica Sinica, 2021, 40(3): 34-45. doi: 10.1007/s13131-021-1710-9

doi: 10.1007/s13131-021-1710-9

Observational characteristics and dynamic mechanism of low-salinity water lens for the offshore detachment of the Changjiang River diluted water in August 2006

Funds: The National Natural Science Foundation of China under contract No. 41376012.
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  • Figure  1.  Surface salinity distribution observed in the summer of 2006 with gray circles showing the observation sites (a) , and vertical salinity distribution along Line A (b). The red triangle in a indicates the center of the LSWL; and the thick solid line in b is the 22 isohaline.

    Figure  2.  Surface temperature distribution observed in the summer of 2006 with gray circles showing the observation sites (a), and vertical temperature distribution along Line A (b). The red triangle in a indicates the center of the LSWL, and the thick solid line in b is the 25°C isotherm.

    Figure  3.  $\sigma $ coordinate for the current calculation (a), and $\sigma {\text{-}} z$ coordinate for the salinity calculation (b).

    Figure  4.  Map of the East China Sea, the Yellow Sea and the Bohai Sea (a), and model domain and horizontal curvilinear coordinate system (b). Bathymetry contours are given in unit of m.

    Figure  5.  Surface distribution of salinity in CASE06 at 03:00 on August 3 (a) , 02:00 on August 7 (b), 01:00 on August 12 (c) and 00:00 on August 19 (d).

    Figure  6.  Average wind vectors during August 2 to 6 (a), August 7 to 11 (b), August 12 to 16 (c) and August 17 to 21 (d).

    Figure  7.  Distributions of the 5-day average velocity in the 0–10 m layer during August 2 to 6 (a), August 7 to 11 (b), August 12 to 16 (c) and August 17 to 21 (d). Dashed lines are the 30 m and 50 m isobaths. Filled contours indicate the distribution of the vertical velocity. The vectors represent the Eulerian residual current.

    Figure  8.  Simulated surface salinity at 05:00 on August 7 in CASE06b.

    Figure  9.  Tide level at Lühuashan station from August 1 to 31 in 2006 (the reference level is the average sea level).

    Figure  10.  Vertical distributions of salinity along Line B in CASE06 on August 3 (a), August 7 (b) and August 10 (c).

    Figure  11.  Surface distributions of salinity in CASE06d at 18:00 on August 4 (a) and in CASE06e at 01:00 on August 12 (b).

    Figure  12.  Vertical salinity and upwelling distributions along Line C (marked in Fig. 5c) in CASE06. The upwelling is the average result from August 7 to 11. The upwelling velocity is amplified by a factor of 104. Salinity is the simulated result at 01:00 on August 12.

    Figure  13.  Surface distribution of salinity in CASE06f at 01:00 on August 13 (a) and in CASE06g at 05:00 on August 6 (b).

    Figure  14.  Distribution of the 5-day average vertical velocity in the 0–10 m layer during August 7 to 11 in CASE06h. Dashed lines are the 30 m and 50 m isobaths.

    Figure  15.  Distribution of vertical velocity in the 0–10 m layer on August 3, 7, and 10 simulated by CASE06i. Dashed lines are the 30 m and 50 m isobaths.

    Figure  16.  Distribution of bottom currents (vectors, $\sigma $=–0.93) on August 10 simulated by CASE06k. Blue dashed lines are the 30 m and 50 m isobaths.

    Table  1.   Summary of the numerical experiments conducted to analyze the LSWL detachment mechanism1)

    CaseWindTideVertical mixingVertical velocityBaroclinity
    CASE06YYYYY
    CASE06aNYYYY
    CASE06b Y2)YYYY
    CASE06cYNYYY
    CASE06dYYNYY
    CASE06eYYYNY
    CASE06fYYYYN
    CASE06gYYYY Y3)
    Note: 1) Y means that the dynamic factors are considered in the simulation, and N means that dynamic factors are excluded from the simulation. 2) The wind is changed to a steady southerly wind of 4 m/s. 3) The BPG is calculated by the climatological average of the salinity and sea temperature.
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    Table  2.   Summary of the numerical experiments conducted to analyze the upwelling mechanism1)

    CaseBaroclinityWindTideRiver discharge and open boundary current
    CASE06hN2)YYY
    CASE06iN2)NYY
    CASE06jN2)YNY
    CASE06kN2)NYN
    Note: 1) Y means that the dynamic factors were considered in the simulation, and N means that the dynamic factors were excluded from the simulation. 2) The salinity of this experiment was fixed and the BPG was set to 0.
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出版历程
  • 收稿日期:  2020-04-13
  • 录用日期:  2020-06-22
  • 网络出版日期:  2021-04-30
  • 刊出日期:  2021-04-30

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