中文摘要：

通过2组线性平流试验，分析随地形复杂度和空间分辨率增加，正交地形追随坐标系（OS坐标）中平流误差的变化．第一组试验采用3种地形，即：单峰、三峰和五峰的波状地形，第二组试验采用5种水平（垂直）分辨率，对比分析OS坐标和经典地形追随坐标系的混合版本（HS坐标）的平流误差．第一组多地形试验表明：单峰试验中，OS坐标与HS坐标的平流误差接近；三峰试验中，OS坐标的平流误差略小于HS坐标的平流误差；五峰试验中，OS坐标的平流误差远小于HS坐标的平流误差．其原因是，HS坐标生成的非正交网格，与OS坐标生成的正交网格，在五峰地形条件下差异最明显．这说明，在简单地形条件下，由于OS坐标和HS坐标的网格差异小，OS坐标减小平流误差的效果不明显，在复杂地形条件下，两者计算网格差异明显，相比HS坐标，OS坐标能显著减小平流误差．第二组多分辨率试验表明：OS坐标的平流误差始终小于HS坐标的平流误差，且垂直分辨率越高，效果越明显．两组理想试验的结果说明，OS坐标有可能减小高分辨率模式中，复杂地形区域的平流误差．

英文摘要：

The orthogonal curvilinear terrain-following coordinate （OS-coordinate） can create smooth vertical layers and orthogonal vertical computational grids, therefore reducing the advection errors in the classic terrain-following coordinate. The reduction of advection errors by the OS-coordinate had been validated by the idealized experiments using one kind of terrain and one kind of resolution. We have implemented two more types of 2D linear advection experiments to further analyze the advection errors of the OS-coordinate. The first experiment is to use three kinds of terrain which are one-crest, three-crest, and five-crest wavelike terrain （multi-mountain experiment）. And the second experiment is to use five different horizontal （vertical） resolutions （multi-resolution experiment）. In both types of the experiments, we compare the advection errors in the OS-coordinate with those in the corresponding hybrid terrain- following coordinate （HS-coordinate） to investigate the effect of the OS-coordinate on reducing the advection errors. For the multi- mountain experiment, the advection errors in the OS-coordinate and those in the HS-coordinate are almost the same in one-crest terrain experiments. And in the three-crest terrain experiments, the advection errors in the OS-coordinate are slightly smaller than those in the HS-coordinate. However, in the five-crest terrain experiment （complex terrain）, the advection errors in the OS-coordinate are much reduced comparing with those in the HS-coordinate. This reason is that the OS-coordinate creates the orthogonal computational grids while the HS-coordinate creates the non-orthogonal computational grids. And the differences between these two grids are most significant in the five-crest terrain experiments. Moreover, the differences between these two grids actually represent the different quality of them. This indicates that the OS-coordinate can reduce the advection errors comparing with the corresponding hybrid terrain-following coordinate above the compl