Application of a modified tidal harmonic analysis method in the analysis of short-term tide levels offshore Zhejiang
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摘要: 传统调和分析方法受限于瑞利准则,需半年数据以分辩八大主要分潮(M2,S2,N2,K2,K1,O1,P1,Q1)。对于短期潮位资料,未分辩的分潮需采用附近长期潮位站资料的差比关系来推算。而浙江近海公开的长期潮位资料匮乏,使得无法从短期资料中准确提取主要分潮。本文引入的新型潮汐调和分析算法,基于各主要分潮间内在联系所建立的平滑函数,突破瑞利准则限制,显著减少了所需潮位资料长度,特别适用于短期资料丰富的海域。本研究将该算法应用于浙江沿海多岛屿海域,对小于15天的潮位资料进行试验。结果表明:石浦站八大主要分潮的调和常数与传统调和分析方法得到的结果总体接近,而所需资料长度从
8760 小时减少至336小时,可用于理论深度基准面等特征参数的计算。采用该算法分析浙江沿海潮位的八大主要分潮时,建议数据长度在5天以上。Abstract: Due to the limitations of the Rayleigh criterion, classical harmonic analysis (CHA) model requires half a year of data records to analyze the eight main tidal constituents, namely, M2, S2, N2, K2, K1, O1, P1, Q1. For short-term tidal records, the unresolved constituents typically rely on the ratio differences from nearby long-term tidal stations for estimation. However, there is a scarcity of publicly available long-term tidal data in the coastal areas of Zhejiang, which currently prevents the accurate extraction of the main constituents from short-term records. This paper introduces a modified harmonic analysis model, referred to as the Modified Harmonic Analysis model based on the Credo of Smoothness (MHACS). Based on the smooth functions established by the intrinsic connections between major constituents, it breaks through the Rayleigh criterion, significantly reducing the length of tidal records required, especially suitable for coastal areas with abundant short-term data. This algorithm was applied to the multi-island area of Zhejiang offshore, using tidal records shorter than 15 days. The results show that the harmonic constants of the eight main constituents at the Shipu station are very close to the results obtained by the CHA method, and the required data length is reduced from8760 hours to 336 hours, which can be used to calculate characteristic parameters such as the theoretical depth datum. For analyzing the eight main constituents along the Zhejiang coast using MHACS, a minimum data length of 5 days is recommended.-
Key words:
- Zhejiang offshore /
- multi-island /
- short-term tidal records /
- harmonic analysis /
- tidal admittance
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表 1 潮位站信息
Tab. 1 The information of tide gauges
站点名称 编号 纬度(°N) 经度(°E) 站点名称 编号 纬度(°N) 经度(°E) 金塘 1 29.99 121.84 峙南 11 29.84 122.06 毛礁 2 29.93 121.87 黄牛礁 12 29.68 121.82 万华码头 3 29.94 121.95 西泽 13 29.63 121.85 定海 4 30.00 122.05 澉浦 14 30.37 120.90 双合 5 30.29 122.06 镇海口 15 29.95 121.72 衢山 6 30.44 122.28 石浦 16 29.23 121.96 泗礁 7 30.72 122.51 岱山 17 30.28 122.22 嵊山 8 30.72 122.80 下三山 18 29.94 121.85 独山码头 9 30.66 121.21 乍浦 10 30.59 121.10 石浦 16 29.23 121.96 表 2 各回归方法下石浦站的调和常数矢量差统计(单位:cm)
Tab. 2 Vector differences of harmonic constants using different regression methods
插值函数 线性函数 二次函数 求解方法 普通最小二乘法 迭代重加权最小二乘法 岭回归法 普通最小二乘法 迭代重加权最小二乘法 岭回归法 矢量差 4.17 3.60 4.11 6.05 7.19 4.13 表 3 石浦站采用经典调和分析CHA方法(1年数据)、EOT20模型和新型调和分析MHACS方法(336小时数据)得到的调和常数(单位:cm,°)
Tab. 3 Estimated tidal amplitudes (cm) and phase lags (degree) at Shipu using CHA (one-year records) , EOT20 model and MHACS (336 hours records) methods
分潮名称 石浦站振幅(迟角) CHA方法 EOT20模型 MHACS方法 M2 145.23(246.08°) 145.00(246.10°) 140.87(244.05°) S2 60.65(291.02°) 60.08(290.16°) 61.25(290.42°) N2 26.86(227.94°) 27.34(224.05°) 33.89(227.42°) K2 16.65(285.47°) 15.94(286.90°) 17.36(294.00°) K1 29.93(209.30°) 29.34(208.12°) 32.15(205.73°) O1 21.58(169.07°) 21.01(168.11°) 22.88(164.01°) P1 8.69(207.32°) 8.68(203.41°) 10.05(202.56°) Q1 3.79(150.15°) 4.22(143.26°) 5.22(149.45°) 表 4 石浦站不同调和分析方法的回报结果比较
Tab. 4 The performances of CHA and MHACS methods at Shipu
方法 解释的信号方差 (%) 均方根误差 (m) 最大误差 (m) CHA方法 94.6 0.28 1.01 MHACS方法 94.7 0.29 0.94 表 5 MHACS方法与EOT20模型得到的18个站位分潮振幅误差比较
Tab. 5 Comparison of the amplitude errors of 18 stations obtained from the MHACS method and the EOT20 model
分潮名称 均方根误差RMSE(m) 最大误差MAE(m) M2 0.27 0.65 S2 0.12 0.25 K1 0.03 0.09 O1 0.02 0.03 表 6 利用MHACS结果计算的浙江近海理论深度基准面值(cm)
Tab. 6 Theoretical depth datum calculated using MHACS results in the coastal area of Zhejiang
站点名称 金塘 毛礁 万华 定海 双合 衢山 泗礁 嵊山 独山 理基值 −194 −185 −180 −181 −100 −204 −203 −208 −406 站点名称 乍浦 峙南 黄牛礁 西泽 澉浦 镇海 石浦 岱山 下三山 理基值 −428 −212 −256 −265 −499 −183 −283 −173 −181 表 7 浙江近海各站位潮汐类型及潮型系数
Tab. 7 Tidal types and daily form factor values using MHACS results in the coastal area of Zhejiang
站点名称 金塘 毛礁 万华 定海 双合 衢山 泗礁 嵊山 独山 F 0.56 0.60 0.63 0.59 0.67 0.47 0.42 0.42 0.24 类型 不正规半日潮 不正规半日潮 不正规半日潮 不正规半日潮 不正规半日潮 半日潮 半日潮 半日潮 半日潮 站点名称 乍浦 峙南 黄牛礁 西泽 澉浦 镇海 石浦 岱山 下三山 F 0.23 0.52 0.43 0.42 0.19 0.62 0.39 0.57 0.59 类型 半日潮 半日潮 半日潮 半日潮 半日潮 不正规半日潮 半日潮 不正规半日潮 不正规半日潮 表 8 浙江近海各站位月潮汐包络因子E值
Tab. 8 The monthly tidal envelope factor E at various stations in the coastal area of Zhejiang
站点名称 金塘 毛礁 万华 定海 双合 衢山 泗礁 嵊山 独山 E 0.91 0.91 0.92 0.91 0.87 0.87 0.84 0.84 0.91 站点名称 乍浦 峙南 黄牛礁 西泽 澉浦 镇海 石浦 岱山 下三山 E 0.91 0.87 0.86 0.86 0.91 0.93 0.86 0.90 0.92 -
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