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IOD and ENSO impacts on the extreme stream-flows of Citarum river in Indonesia |
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| Authors: | Netrananda Sahu Swadhin K Behera Yosuke Yamashiki Kaoru Takara Toshio Yamagata |
| Institution: | 1. Disaster Prevention Research Institute, Innovative Disaster Prevention Technology and Policy Research Laboratory, Kyoto University, Gokasho, Uji City, Kyoto, 611-0011, Japan 2. Research Institute for Global Change, JAMSTEC, 3173-25 Showamachi, Yokohama, Kanagawa, 236-0001, Japan 4. Application Laboratory, JAMSTEC, Yokohama, Japan 3. School of Science, University of Tokyo, 3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan |
| Abstract: | Extreme stream-flow events of Citarum River are derived from the daily stream-flows at the Nanjung gauge station. Those events are identified based on their persistently extreme flows for 6 or more days during boreal fall when the seasonal mean stream-flow starts peaking-up from the lowest seasonal flows of June–August. Most of the extreme events of high-streamflows were related to La Ni?a conditions of tropical Pacific. A few of them were also associated with the negative phases of IOD and the newly identified El Ni?o Modoki. Unlike the cases of extreme high streamflows, extreme low streamflow events are seen to be associated with the positive IODs. Nevertheless, it was also found that the low-stream-flow events related to positive IOD events were also associated with El Ni?o events except for one independent event of 1977. Because the occurrence season coincides the peak season of IOD, not only the picked extreme events are seen to fall under the IOD seasons but also there exists a statistically significant correlation of 0.51 between the seasonal IOD index and the seasonal streamflows. There also exists a significant lag correlation when IOD of June–August season leads the streamflows of September–November. A significant but lower correlation coefficient (0.39) is also found between the seasonal streamflow and El Ni?o for September–November season only. |
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