Observed seasonality of M2 and M4 tidal currents in the Gulf of Khambhat using high-frequency radars

IF 2.2 3区地球科学 Q2 OCEANOGRAPHY Ocean Dynamics Pub Date : 2024-02-02 DOI:10.1007/s10236-024-01601-2

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Abstract

This study presents the initial findings from analyzing the ocean surface current observations during 2018 from the recently installed high-frequency (HF) radars in the Gulf of Khambhat in the northeastern Arabian Sea, India. The research is structured into two main sections: firstly, the extraction of the major (M2, S2, N2, K1, and O1) and shallow-water (M4, MS4, M6, and M8) tidal currents in the gulf, and secondly, understanding the impact of seasonal riverine freshwater influxes on the M2 tidal currents. The HF radars accurately captured strongest currents of ~2.0 m/s within the gulf. Additionally, the circulation pattern in the western gulf is mostly characterized by zonal currents, in contrast to the eastern gulf, where meridional currents prevail. Based on the findings of the higher harmonic analysis, it is apparent that the M2 tidal currents exhibit the highest magnitude, followed by other semi-daily constituents such as S2 and N2, as well as diurnal tidal constituents including K1 and O1. The M4 tidal currents, which are one of the shallow-water tidal components, exhibit strengths that span from 3.15 to 16.50 cm/s. The enhancement of tidal currents in the nearshore areas (within approximately 50 m) can be attributed to their interaction with the bottom bathymetry and the general coastline geometry of the gulf. Notably, higher values of Richardson number ( \({R}_{i}\) ) and Brunt-Väisälä frequency ( \({N}^{2}\) ) indicated the presence of highly stratified upper layers, particularly during September. The signatures of higher stratification during September contribute to the highest amplitude (>1.50 m/s) of M2 tidal currents.

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利用高频雷达观测康巴特湾 M2 和 M4 潮汐的季节性变化

摘要本研究介绍了对 2018 年期间印度阿拉伯海东北部坎巴特湾最近安装的高频（HF）雷达的洋面海流观测数据进行分析的初步结果。研究分为两个主要部分：首先，提取海湾中的主要（M2、S2、N2、K1 和 O1）和浅水（M4、MS4、M6 和 M8）潮流；其次，了解季节性河流淡水流入对 M2 潮流的影响。高频雷达准确捕捉到了海湾内 ~2.0 m/s 的最强潮流。此外，海湾西部的环流模式主要以带状流为特征，而海湾东部则以经向流为主。根据高次谐波分析结果，显然 M2 潮汐流的波幅最大，其次是 S2 和 N2 等其他半日潮成分，以及 K1 和 O1 等昼夜潮成分。M4 潮流是浅水潮汐成分之一，其强度从 3.15 厘米/秒到 16.50 厘米/秒不等。近岸区域（约 50 米范围内）潮汐流的增强可归因于其与海底水深和海湾一般海岸线几何形状的相互作用。值得注意的是，理查森数（{R}_{i}\）和布伦特-韦赛莱频率（{N}^{2}\）的数值较高，表明存在高度分层的上层，尤其是在 9 月份。9月份较高的分层特征导致了M2潮流的最高振幅（1.50米/秒）。

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来源期刊

Ocean Dynamics 地学-海洋学

CiteScore

5.40

自引率

0.00%

发文量

审稿时长

6-12 weeks

期刊介绍： Ocean Dynamics is an international journal that aims to publish high-quality peer-reviewed articles in the following areas of research: Theoretical oceanography (new theoretical concepts that further system understanding with a strong view to applicability for operational or monitoring purposes); Computational oceanography (all aspects of ocean modeling and data analysis); Observational oceanography (new techniques or systematic approaches in measuring oceanic variables, including all aspects of monitoring the state of the ocean); Articles with an interdisciplinary character that encompass research in the fields of biological, chemical and physical oceanography are especially encouraged.