3:45 PM - 4:00 PM
[AOS14-07] A high-resolution numerical model at the Oshima Strait
Keywords:A high-resolution numerical model , The Oshima Strait, FVCOM
1, Introduction
The Oshima strait is located the southwest of Japan, between Amami island and Kakeroma island, is famous for aquaculture owing to calm sea.It is significant to forecast sea conditions at the Oshima Strait to actualize efficiency of feed managements for red tide and inflow of low-oxygen water pathways to aquaculture farms. DREAMS_E (Kuroshio conditions forecast model, 1.5 km x 1.5 km space) is not forecasting the sea condition at the Oshima Strait owing to too narrow. This research builds a high-resolution numerical model to forecast sea conditions at the Oshima Strait.
2, Model Description
In this research, Finite Volume Community Ocean Model (FVCOM), which can show clearly coastal and submarine topography was used. Coastal and submarine topography data used calculations were obtained from M7000 series of the Japan Hydrographic Association. Submarine topography data were obtained from observations conducted by our laboratory were also added. The grid width is about 200m at boundary, and the minimum grid is about 50m. Vertical direction separates σ coordinate system 10 layers. The sea temperature and salinity in the Oshima Strait given as initial conditions were calculated to linear interpolation DREAMS_E data which closest point to the strait. The sea temperature, salinity, sea level and current velocity of DREAMS_E were given to the boundary. Besides, the heat budget of sea surface and wind stress were calculated using COARE.ver2.6. Evaporation was calculated based on Kondo’s equation (1975). Meteorological data were obtained from the meteorological elements of MSM-GPV. However, regarding the calculation of reproducibility of observed current velocity in 2010 and 2013, meteorological observation data from the Nase meteorological station was used.
3, Comparison of observed and calculated value (sea level, current velocity, seawater temperature)
Comparison of calculated and observed results of sea levels. Overall, although the calculated values underestimate the observed values, the phase matches. The correlation coefficient is 0.93, and RMSE is 0.18m. The reproducibility of sea level indicates high.
Next, comparison of calculated and observed results of ADCP fixed point current velocity.When red tide occurs or low-oxygen water flows in, some tuna aquacultures discard a portion of feed, as the tuna cease feeding. Overall, although the calculated values underestimate the observed values, the phase matches. The correlation coefficient is 0.87, and RMSE is 0.32m/s. The calculated results of current direction were slightly southerly during the rising tide and slightly northerly during the falling tide, compared to the observed results.
In addition, comparison of calculated and observed results of towing current velocity. The qualitative characteristics of strong currents were reproducibility like tailed for current direction. However, both the rising and falling tides, the calculated results underestimate the observed results.
Finaly, comparison of calculated and observed results of seawater temperature. The calculated values underestimated the observed values, while after the latter half, the results were mostly the same.
4, Summary
To sum up, sea conditions forecasting model at the Oshima Strait was built as a prototype model using sea condition forecast data of DREAMS_E and meteorological forecast data of MSM. In terms of tidal component about sea level and current velocity the calculated results underestimated the observed results. This could be caused by the small tidal fluctuations of DREAMS_E given to the boundary. Although the calculated results of seawater temperature also underestimated the observed results, it shows the possibility of reproducing short-period variations. Our future prospect is to research the case of using DREAMS_Ep (the sea conditions forecast model) given to the boundary.
The Oshima strait is located the southwest of Japan, between Amami island and Kakeroma island, is famous for aquaculture owing to calm sea.It is significant to forecast sea conditions at the Oshima Strait to actualize efficiency of feed managements for red tide and inflow of low-oxygen water pathways to aquaculture farms. DREAMS_E (Kuroshio conditions forecast model, 1.5 km x 1.5 km space) is not forecasting the sea condition at the Oshima Strait owing to too narrow. This research builds a high-resolution numerical model to forecast sea conditions at the Oshima Strait.
2, Model Description
In this research, Finite Volume Community Ocean Model (FVCOM), which can show clearly coastal and submarine topography was used. Coastal and submarine topography data used calculations were obtained from M7000 series of the Japan Hydrographic Association. Submarine topography data were obtained from observations conducted by our laboratory were also added. The grid width is about 200m at boundary, and the minimum grid is about 50m. Vertical direction separates σ coordinate system 10 layers. The sea temperature and salinity in the Oshima Strait given as initial conditions were calculated to linear interpolation DREAMS_E data which closest point to the strait. The sea temperature, salinity, sea level and current velocity of DREAMS_E were given to the boundary. Besides, the heat budget of sea surface and wind stress were calculated using COARE.ver2.6. Evaporation was calculated based on Kondo’s equation (1975). Meteorological data were obtained from the meteorological elements of MSM-GPV. However, regarding the calculation of reproducibility of observed current velocity in 2010 and 2013, meteorological observation data from the Nase meteorological station was used.
3, Comparison of observed and calculated value (sea level, current velocity, seawater temperature)
Comparison of calculated and observed results of sea levels. Overall, although the calculated values underestimate the observed values, the phase matches. The correlation coefficient is 0.93, and RMSE is 0.18m. The reproducibility of sea level indicates high.
Next, comparison of calculated and observed results of ADCP fixed point current velocity.When red tide occurs or low-oxygen water flows in, some tuna aquacultures discard a portion of feed, as the tuna cease feeding. Overall, although the calculated values underestimate the observed values, the phase matches. The correlation coefficient is 0.87, and RMSE is 0.32m/s. The calculated results of current direction were slightly southerly during the rising tide and slightly northerly during the falling tide, compared to the observed results.
In addition, comparison of calculated and observed results of towing current velocity. The qualitative characteristics of strong currents were reproducibility like tailed for current direction. However, both the rising and falling tides, the calculated results underestimate the observed results.
Finaly, comparison of calculated and observed results of seawater temperature. The calculated values underestimated the observed values, while after the latter half, the results were mostly the same.
4, Summary
To sum up, sea conditions forecasting model at the Oshima Strait was built as a prototype model using sea condition forecast data of DREAMS_E and meteorological forecast data of MSM. In terms of tidal component about sea level and current velocity the calculated results underestimated the observed results. This could be caused by the small tidal fluctuations of DREAMS_E given to the boundary. Although the calculated results of seawater temperature also underestimated the observed results, it shows the possibility of reproducing short-period variations. Our future prospect is to research the case of using DREAMS_Ep (the sea conditions forecast model) given to the boundary.