Study on spatial-temporal distribution characteristics of tidal skewness in the Wenzhou Bay
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摘要: 人类活动引起的岸线变化影响着近岸海域的潮波在传播过程中的运动特征。本研究基于瓯江口与乐清湾5个验潮站,时间跨度为1984−2019年的逐时潮位实测资料,分析了该海域潮波形态的时空变化规律并解构造成潮汐不对称性的主要分潮簇的贡献度。研究发现,温州湾海域瓯江河口与乐清湾潮形有明显的不同,潮汐不对称性在瓯江河口涨潮占优,且向上游方向持续增大,但在乐清湾内则落潮占优。该海域潮汐不对称性呈现出明显的季节性变化特征。在6−7月、12月至翌年1月时
$ \gamma $ 值达到最大。该海域潮汐不对称性主要由分潮组合M2/M4、M2/S2/MS4、M2/N2/MN4等分潮簇控制,分潮簇如M2/S2/MS4、M2/N2/MN4、O1/K1/M2的不对 称贡献度则表现出明显的季节性变化。从2000年起,温州湾海域涨潮占优的潮汐不对称性呈现逐渐减弱的趋势,这与瓯江河口频繁的海岸工程存在一定的联系。Abstract: The changes of shoreline caused by human activities affect the kinematic characteristics of tidal wave in the propagation process. Based on the hourly tidal level data from five tidal stations in the Wenzhou Bay from 1984 to 2019, the temporal and spatial variation of tidal wave patterns in this area and deconstructed the contribution of major tidal clusters to the tidal asymmetry is analyzed in this study . The results show that the tidal patterns in Oujiang Estuary and Yueqing Bay, two semi-enclosed embayments of the Wenzhou Bay, are obviously different. The tidal symmetry of Oujiang Estuary is flood-dominant tide and the tidal asymmetry increases continuously in the upstream direction, whilst tide is ebb-dominant in Yueqing Bay. Moreover, the tidal asymmetry shows distinct seasonal variation. The skewness ($ \gamma $ ) reaches maximum in June to July and December to January in the Wenzhou Bay. The tidal asymmetry in this area is mainly controlled by the component groups such as M2/M4, M2/S2/MS4 and M2/N2/MN4. The skewness caused by nonlinear interactions from M2/S2/MS4, M2/N2/MN4, O1/K1/M2 shows obvious seasonal variation. Since 2000, the tidal asymmetry of Wenzhou Bay has been decreasing, which is related to the frequent reclamation surrounding the Oujiang Estuary.-
Key words:
- tidal skewness /
- Wenzhou Bay /
- tidal clusters /
- shoreline changes /
- seasonal variability /
- yearly variability /
- flood-dry seasons
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图 5 2019年温州海域每月总降雨量(a)、2019年各测站枯汛期偏度比较(b)和温州站历年枯汛期偏度比较(c)
Fig. 5 Precipitation over year 2019 in Wenzhou waters (a), scatter plots of tidal skewness in flooding season vs. dry season at different stations (b) and scatter plots of tidal skewness in flooding season vs. dry season at Wenzhou Station for different years (c)
图 6 2019年各测站最主要3大分潮簇对潮汐不对称性的贡献度月际变化
a. 测站年均β值最大的分潮组合;b. 测站年均β值第二的分潮组合;c. 测站年均β值第三的分潮组合
Fig. 6 Monthly variability of the contribution to tidal duration asymmetry from the top three primary combinations of tidal constituents at each station in 2019
a. The tidal combination with the largest annual average β value of the station; b. the tidal combination with the second annual average β value of the station; c. the third tidal combination with the third annual average β value of the station
图 7 2019年各测站3大分潮簇对潮汐不对称性的月均贡献度与年均贡献度比值
a. 测站年均β值最大的分潮组合;b. 测站年均β值第二的分潮组合;c. 测站年均β值第三的分潮组合
Fig. 7 The ratio of monthly contribution to tidal duration asymmetry over annual contribution to tidal duration asymmetry by the top three primary combinations of tidal constituents at each station in 2019
a. The tidal combination with the largest annual average β value of the station; b. the tidal combination with the second annual average β value of the station; c. the third tidal combination with the third annual average β value of the station
图 9 温州站 2000−2019 年典型月份主要分潮簇对潮汐不对称性的贡献β值及偏态指标γ值 Mann-Kendall 跃变检验结果
Fig. 9 Test result of Mann-Kendall break of contribution to tidal duration asymmetry from the primary combinations of tidal constituents denoted by β and tidal skewness index (γ) in typical months at Wenzhou Station from year 2000 to 2019
表 1 2019年各测站潮波基本特征
Tab. 1 Characteristics of tidal wave at each station in 2019
测站 南麂山 大门岛 龙湾 温州 东门村 最大潮差/m 7.15 8.04 8.19 7.53 8.56 最大潮差发生时间(月/日) 7/3 7/3 7/3 7/3 7/4 最小潮差/m 1.41 1.56 1.99 2.22 1.70 最小潮差发生时间(月/日) 12/6 12/6 1/29 12/6 2/28 年均潮汐偏度($ \mathrm{\gamma } $) 0.03 0.05 0.25 0.43 −0.16 表 2 各测站2019年7个主要分潮簇
Tab. 2 The seven primary combinations of tidal constituents at each station in 2019
分潮簇 南麂山站 大门岛站 龙湾站 温州站 东门村站 1 O1/K1/M2 M2/S2/MS4 M2/M4 M2/M4 M2/M4 2 M2/S2/MS4 O1/K1/M2 M2/S2/MS4 M2/S2/MS4 M2/S2/MS4 3 K1/M2/MK3 M2/M4 M2/N2/MN4 M2/N2/MN4 O1/K1/M2 4 M2/O1/MO3 M2/K1/MK3 M2/K1/MK3 M2/M4/M6 K1/P1/S2 5 M2/N2/MN4 M2/O1/MO3 M2/K2/MK4 M2/MS4/2MS6 K1/K2 6 K1/P1/S2 M2/N2/MN4 M2/K1/O1 MU2/S2/M4 MU2/S2/M4 7 M2/K2/MK4 S2/S4 M2/O1/MO3 M2/K2/MK4 M2/M4/M6 表 3 温州站2000−2019年6月和11月份主要分潮簇对潮汐不对称性贡献值及月潮位偏度Mann-Kendall检验值
Tab. 3 Mann-Kendall test value of contributions to tidal duration asymmetry by primary combinations of tidal constituents and tidal skewness at Wenzhou Station in June and November over 2000 to 2019
时间 β−M2/M4 β−M2/S2/MS4 β−M2/N2/MN4 γ 6月 −4.44 −0.68 −0.68 −3.21 11月 −2.95 −1.46 −0.36 −2.24 -
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