Abstract The present study analyzed 41 years of ERA-5 wind-wave data (1979–2019) to understand the long-term trend, inter-annual, and inter-seasonal variability of total wind-generated waves, wind-seas, and swell waves in the Indian Ocean (IO). The significant wave height (SWH) of ERA-5 was validated with the multi-platform calibrated altimetry wave height. The correlation coefficient of SWH was about 0.97 considering the entire domain, and it is greater than 0.9 for different sectors in the IO basin. The absolute and root mean square errors in different sub-domains are observed in the range of 0.16–0.3 m and 0.2–0.37 m, respectively and found higher in the extra tropical IO (ETSI). The ETSI showed an increasing trend for both wind-seas and swell waves (0.5–1 cm/year). In context to wind-seas, shift in the westerly wind belt leads to pole-ward increasing and equator-ward decreasing trend. In the northern Arabian Sea, the swell waves exhibited an increasing trend (0.8 cm/year) during the south-west monsoon. Meanwhile, the wind-sea activity over the Arabian Sea and Head Bay of Bengal are seen to decrease. The regions in the IO that experienced higher variability of SWH in the last four decades are identified using EOF (Empirical Orthogonal Function) analysis. The dominant mode of Principal Component Analysis signified the explicit contribution of swell waves over the total significant wave height. The second and third modes of variability are majorly contributed by wind-seas, especially in the south IO attributed due to the Southern Annular Mode (SAM). The wavelet spectrum analysis conducted at the identified locations of higher variability manifests the domain sensitivity by which the Makran coast experienced an increased average variance in annular and semi-annular scales.

中文翻译：

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使用 ERA-5 数据集的印度洋风波气候变化

摘要 本研究分析了 ERA-5 41 年的风浪数据（1979-2019），以了解总风浪、风海和涌浪的长期趋势、年际和季节间变化。印度洋 (IO) 的波浪。ERA-5 的有效波高 (SWH) 通过多平台校准测高波高进行验证。考虑到整个域，SWH 的相关系数约为 0.97，对于 IO 流域的不同扇区，相关系数大于 0.9。不同子域中的绝对和均方根误差分别在 0.16-0.3 m 和 0.2-0.37 m 范围内观察到，并且在额外热带 IO (ETSI) 中发现更高。ETSI 显示出风-海和涌浪（0.5-1 厘米/年）的增加趋势。在风海的背景下，西风带的移动导致向极地增加和向赤道减少的趋势。在阿拉伯海北部，西南季风期间涌浪呈增加趋势（0.8 cm/年）。与此同时，阿拉伯海和孟加拉海德湾上空的风-海活动减少。使用EOF（经验正交函数）分析确定了在过去四个十年中经历了 SWH 更高变异性的 IO 区域。主成分分析的主导模式表示涌浪对总有效波高的显着贡献。第二和第三变率模态主要由风-海贡献，特别是在南 IO 归因于南环形模态 (SAM)。