Modeling of extreme freshwater outflow from the north-eastern Japanese river basins to western Pacific Ocean

Troselj, Josko, Sayama, Takahiro, Varlamov, Sergey M., Sasaki, Toshiharu, Racault, Marie-Fanny, Takara, Kaoru, Miyazawa, Yasumasa, Kuroki, Ryusuke, Yamagata, Toshio and Yamashiki, Yosuke (2017) Modeling of extreme freshwater outflow from the north-eastern Japanese river basins to western Pacific Ocean. Journal of Hydrology, 555. pp. 956-970. ISSN 0022-1694

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Abstract

This study demonstrates the importance of accurate extreme discharge input in hydrological and oceanographic combined modeling by introducing two extreme typhoon events. We investigated the effects of extreme freshwater outflow events from river mouths on sea surface salinity distribution (SSS) in the coastal zone of the north-eastern Japan. Previous studies have used observed discharge at the river mouth, as well as seasonally averaged inter-annual, annual, monthly or daily simulated data. Here, we reproduced the hourly peak discharge during two typhoon events for a targeted set of nine rivers and compared their impact on SSS in the coastal zone based on observed, climatological and simulated freshwater outflows in conjunction with verification of the results using satellite remote-sensing data. We created a set of hourly simulated freshwater outflow data from nine first-class Japanese river basins flowing to the western Pacific Ocean for the two targeted typhoon events (Chataan and Roke) and used it with the integrated hydrological (CDRMV3.1.1) and oceanographic (JCOPE-T) model, to compare the case using climatological mean monthly discharges as freshwater input from rivers with the case using our hydrological model simulated discharges. By using the CDRMV model optimized with the SCE-UA method, we successfully reproduced hindcasts for peak discharges of extreme typhoon events at the river mouths and could consider multiple river basin locations. Modeled SSS results were verified by comparison with Chlorophyll-a distribution, observed by satellite remote sensing. The projection of SSS in the coastal zone became more realistic than without including extreme freshwater outflow. These results suggest that our hydrological models with optimized model parameters calibrated to the Typhoon Roke and Chataan cases can be successfully used to predict runoff values from other extreme precipitation events with similar physical characteristics. Proper simulation of extreme typhoon events provides more realistic coastal SSS and may allow a different scenario analysis with various precipitation inputs for developing a nowcasting analysis in the future.

Item Type: Article
Additional Information: Funding Information: This study was supported by Post-K Priority Issue 4 Advancement of meteorological and global environmental predictions utilizing observational ‘Big Data’ where the corresponding author is joining as a member. This study was also supported by the Monbukagakusho ( MEXT ) scholarship and the Kyoto University Global COE program “Human Security Engineering for Asian Megacities” which were funding the Ph.D. degree study of the first author, who also deeply thanks to Professor Nobuhito Mori at DPRI Kyoto University and The Social Implementation Program on Climate Change Adaptation Technology ( SI-CAT ) for recent scientific, operational and financial support. Corresponding author (Y. Yamashiki) and co-authors (T. Sasaki and R. Kuroki) deeply thanks to Professor Hoshin Gupta at University of Arizona for his support in learning SCE-UA method combining into hydrological model. M-F Racault was supported by the Japan Society for the Promotion of Science ( JSPS ) Invitational Fellowship for Research in Japan (Long-term) based upon the invitation of Japanese host Prof. Yamagata. The authors would also like to acknowledge the Ocean Colour Climate Change Initiative dataset, Version 3.1, European Space Agency, available online at http://www.esa-oceancolour-cci.org/ . The authors are grateful to Adrean Webb and Cassandra Wardinsky for providing English proofread of the manuscript. Corresponding author (Y. Yamashiki) is also grateful to the Croatian-Japanese joint research Science and Technology Research Partnership for Sustainable Development (SATREPS) project ‘Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia’ and its Croatian Focal Point Professor Nevenka Ožanić who introduced the first author (J. Troselj) to the corresponding author at first time in 2012. Finally, we thank to the Editor-in-Chief, the Associate Editor and two anonymous Reviewers for their useful comments that greatly improved quality of the paper.
Uncontrolled Keywords: coastal zone,extreme typhoon events,integrated hydrological and oceanographic model,nowcasting,sce-ua optimization method,sea surface salinity distribution,water science and technology ,/dk/atira/pure/subjectarea/asjc/2300/2312
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 14 Feb 2022 13:30
Last Modified: 10 May 2022 16:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/83467
DOI: 10.1016/j.jhydrol.2017.10.042

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