中文摘要：

在地形变化剧烈的海域，由于6坐标在垂向离散出现了较大的压强梯度力误差，导致盐度模拟误差较大。本文在EFDC（Environmental Fluid Dynamics Code）模型的基础上，以美国莫比尔湾（Mobile Bay）2例，比较了在水深变化剧烈的区域。坐标和LCLG坐标下盐度数值模拟结果的差异。研究结果表明，采用LCLσ坐标能使得压强梯度力所产生的截断误差降到最低；在LCLσ坐标下，模拟的趋势和模拟数值都能够真实地反应实际的物理情况，为今后解决此类问题提供了一种新方法。

英文摘要：

In steep topography areas, error in pressure gradient is often big due to the dissociation in vertical direction in a sigma coordinate, which would cause considerable bias in salinity that simulated. To solve this problem, using the Mobile Bay （30° 13′-30°39′N, 87°45′-88°07′W） USA as an example of steep topography, we simulated the salinity of the bay in the EFDC （Environmental Fluid Dynamics Code） model in both sigma and LCL （Laterally Constrained Local- ized）-sigma coordinates. Results show that simulation in the LCL-sigma coordinate could minimize the truncation error that resulted from the pressure gradient force, and produce clear and good simulation results that are consistent with the physical realities. Therefore, we can apply the method for solving similar problems in the future.