Satoshi Nakada, Yoichi Ishikawa, Toshiyuki Awaji, Teiji In, Shigeki Shima, Tomoharu Nakayama, Tomonori Isada, Sei-Ichi Saitoh
Published: May 18, 2012

Modeling runoff into a Region Of Freshwater Influence for improved ocean prediction: Application to Funka Bay
Satoshi Nakada1), Yoichi Ishikawa1) 2), Toshiyuki Awaji1), Teiji In3), Shigeki Shima3), Tomoharu Nakayama3), Tomonori Isada4), Sei-Ichi Saitoh4)

1) Department of Geophysics, Division of Earth and Planetary Sciences, Kyoto University
2) Data Research Center for Marine-Earth Sciences, Japan Agency for Marine-Earth Science and Technology
3) Japan Marine Science Foundation
4) Laboratory of Marine Bioresource and Environment Sensing, Faculty of Fisheries Sciences, Hokkaido University

released J-STAGE 2012/05/18
received 2012/01/20 accepted 2012/03/13

Regions Of Freshwater Influence (ROFI) existing between oceans and estuaries often yield significant fishery resources. To inform fishermen of the real-time ocean state, an operational prediction system focusing on a specific coastal region would normally require accurate and timely runoff data for all rivers. In this paper, hydrometeorological procedures providing the required runoff data on a daily basis were coupled with an Ocean General Circulation Model (OGCM) to evaluate the impacts of runoff processes on ocean simulations within a ROFI. The procedures we adopted employ a distributed tank model based on water mass and heat budgets derived from predicted meteorological datasets. An exponential relationship between runoff rates and watershed areas was used to determine model parameters in order to estimate the runoff from many other small rivers. The coupled model reproduced a surface salinity field in the bay that was in good agreement with observations, and simulated the expected clockwise circulation generated by the high net total discharge associated with snowmelt. Our results underline the fact that implementation of hydrological processes into ocean simulations is essential for a better understanding of water circulation driven by runoff into semi-enclosed bays over interannual timescales.

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