MARS3D / AGRIF model configuration for the Bay of Brest

This repository provides the source code written in Fortran 90 language based on MARS3D model code (Lazure and Dumas, 2008) implemented with the AGRIF library (Adaptive Grid Refinement In Fortran from Debreu et al. (2008)). It also contains the bathymetric grids and the input namelist files. The MARS3D/AGRIF model is setup over the Iroise sea (geographic limits 47.74°N - 48.82°N and 4.08°W - 5.55°W) with a horizontal grid resolution of 250m. A zoom over the Bay of Brest is introduced with a resolution of 50m (geographic limits 48.20°N - 48.44°N and 4.09°W - 4.72°W). The time and space refinement factors are both equal to 5. The vertical discretization is performed with 20 equidistant σ-layers in both grids. The timestep for mother grid is set to 30s which consequently leads to 6s for the child grid. The bathymetries are interpolated from a combination of different digital terrain models (SHOM, Ifremer, IGN). The Iroise model is forced by harmonic components from the SHOM CST-France model (Le Roy and Simon, 2003). The 3D open boundary conditions for temperature and salinity are imposed at hourly frequency from a regional configuration based on a hindcast (Caillaud et al., 2016). Freshwater inputs for the four main rivers in the Bay were taken from the French HYDRO database and corrected with corresponding watershed surface rates The horizontal turbulent closure consists of a Laplacian operator with a constant turbulent viscosity coefficient. This coefficient was set to 0.5 m2 s−1. The vertical turbulent closure is performed using the generalised length-scale parametrisation with a two-equation k-ε model. For the child grid, the surface drag coefficient was set uniformly to obtain the optimum validation of the currents in the Bay of Brest. However, the bottom drag coefficient relied on the Prandtl theory of the bottom boundary layer and its logarithmical shape. It includes in its formulation a classical roughness scale, which was spatialised according to a recent sedimentological map (Gregoire et al. 2016).

本仓库提供基于MARS3D模型（MARS3D model）代码（Lazure与Dumas，2008）、采用AGRIF库（Adaptive Grid Refinement In Fortran，由Debreu等人2008年提出）编写的Fortran 90语言源代码，同时包含水深网格与输入namelist文件。本MARS3D/AGRIF模型构建于伊罗伊斯海（地理范围：47.74°N~48.82°N，4.08°W~5.55°W），水平网格分辨率为250米；针对布雷斯特湾设置了嵌套加密区域，分辨率为50米，其地理范围为48.20°N~48.44°N，4.09°W~4.72°W。该模型的时间与空间加密因子均为5，两套网格均采用20层等距σ坐标系垂直分层。母网格的时间步长设为30秒，因此子网格的时间步长为6秒。水深数据由SHOM、Ifremer、IGN三套数字地形模型融合插值得到。伊罗伊斯海模型的强迫场采用SHOM CST-France模型的谐波分量（Le Roy与Simon，2003）；温度与盐度的三维开边界条件采用基于后报数据集的区域配置结果，每小时更新一次（Caillaud等人，2016）。布雷斯特湾四条主要河流的淡水输入数据取自法国HYDRO数据库，并依据对应流域表面积参数进行了校正。水平湍流闭合方案采用拉普拉斯算子，搭配恒定湍流黏性系数，该系数取值为0.5 m²·s⁻¹。垂直湍流闭合方案采用基于广义长度尺度参数化的两方程k-ε模型。针对子网格，海面拖曳系数统一设置为最优值，以实现布雷斯特湾海流的最优模拟验证；而底拖曳系数则基于普朗特底边界层理论及其对数分布形式构建，该方案的公式中包含经典粗糙度尺度，并依据最新沉积学地图（Gregoire等人，2016）实现了空间分布化。