Abstract
This study investigates the spatial and temporal distribution of FUI and its changes in Japan and its coastal seas from 2013 to 2023 using the Google Earth Engine platform, analyzes the reasons for these changes and provides corresponding recommendations. The results indicate that during this decade, the FUI values in Japan and its coastal seas mainly range from 10 to 15, showing a spatial distribution of relatively high FUI values in the south and relatively low values in the north. Additionally, FUI exhibits obvious seasonality, with values in autumn and winter significantly higher than those in spring and summer, in the order of autumn > winter > spring > summer. From 2013 to 2023, the sea surface temperature has shown an increasing trend, characterized by a similar spatial distribution: high in the south and low in the north, akin to the distribution of FUI. Compared to the period from 2013 to 2018, the changes in FUI from 2018 to 2023 are more positive, indicating a decline in the quality of water bodies in Japan and its coastal seas.
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Acknowledgements
The authors would like to thank the editors and the anonymous reviewers for their constructive comments and suggestions, which greatly helped to improve the quality of the manuscript.
Funding
This work was supported by the Fundamental Research Funds for the Central Universities (Ph.D. Top Innovative Talents Fund of CUMTB), the key program of the National Natural Science Foundation of China (grant number 41930650), and the general program of the National Natural Science Foundation of China (grant number 42271435).
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All authors were involved in the conception and design of the study. Material preparation, data collection, analysis and methodology were carried out by Linye Zhu, Xiaoyi Jiang, Longfei Zhao, Hui Qu, Wenbin Sun, and Haibo Ban. The first draft of the manuscript was written by Linye Zhu and Wenbin Sun, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Zhu, L., Jiang, X., Zhao, L. et al. Changes in remotely sensed Forel-Ule Index for the coastal seas of Japan, 2013–2023. Earth Sci Inform 18, 57 (2025). https://doi.org/10.1007/s12145-024-01507-z
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DOI: https://doi.org/10.1007/s12145-024-01507-z