報告書番号

U02054

タイトル（和文）

沿岸流動モデルのための開境界条件の推定法

タイトル（英文）

Estimation Method for Open Boundary Conditions of Coastal Current Model

概要 （図表や脚注は「報告書全文」に掲載しております）

データ同化の適用により，観測結果から沿岸モデルの開境界条件を推定する手法を開発した.観測結果には，汀線29km×沖合い11kmの海域における15点の流速結果のみを用いた．沿岸流動モデルには，線形・定常な浅水方程式を用い，この開境界での水位を制御変数とした．ペナルティ乗数法を用いて観測結果と計算結果の目的関数を最小化し，制御変数の推定を行った.推定方法を検討するために，２つの同化モデルを構築した．最初の同化モデルでは，数値モデルの格子点全てに観測結果を与える出力モデルを用い，開境界上の全計算点の水位を推定した．次の同化モデルでは，観測点を囲む4つの計算点の結果が観測結果であるとした出力モデルを用い，開境界の水位形状を構成する直交関数の係数を推定した．両モデルによりデータ同化した結果，両モデルともに観測結果にほぼ一致した流動場が計算出来，さらにこの流速場を実現する境界条件を推定できた.

概要 （英文）

The method estimating the open boundaries for a coastal current model from the observational data was developed using the data assimilation approach. The observations available in this study was only the velocity data measured with current-meters at 15 stations in the sea area with about 29km in the alongshore direction × about 11km in the offshore direction. The linear, steady shallow water equation was applied as the coastal current model. The water level along the three open boundaries of this model was set as the control variable. We estimated the control variables by using the penalty multiplier method to minimize the objective function composed of observations and computational results. To study this estimation method, we developed two assimilation models. The first assimilation model used the output model by which the observations were set to all the calculation grids, and estimated the water level on all calculation grids along the open boundaries. The second model used the output model by which the observation was represented by four calculation results around the station, and estimated the coefficients of the orthogonal functions of which linear sum composed the sea level along the open boundaries. The data assimilation was carried out using both models. The calculated flow field agreed with the observed flow pattern, which suggested that the open boundary conditions achieving the flow field were estimated appropriately.

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