This paper, relates the lee vortex which is trig- gered when the rotating and stratified flow passes over the large obstacle by using towing tank and based on the simi- larity. The results show that Froude number Fr is the most important parameter, and, in the rotating case, the lee vortex is easily triggered, because the rotating may, on one hand, lead to downward flow, on the other hand, induce lee vortex through generating geostrophic vorticity. Even in the non-rotating case, the lee vortex can be still formed, as long as both Froude number Fr and stratification parameter N are appropriate. For the formation mechanism of the lee vortex, there are obvious differences in the rotating case compared with the non-rotating case. In the non-rotating case, the tilting term of the perturbation vorticity is a domi- nant factor of inducing the lee vortex. However, in the rotat- ing case, effect and the convergence of perturbation vorticity are dominant factors.
The rainfall over the Yangtze River val- ley during flood seasons (June to July) shows both interannual and decadal variations. The rainfall has been increasing since 1990, showing a decadal sig- nal. The variations of rainfall are influenced by the multi-scale interactions in the atmosphere-ocean coupled climate system. The rainfall, SST, and cir- culation are analyzed with the Chinese 160 station data, and other observational/reanalysis data, re- spectively. The separation between the interannual and decadal variations is carried out. The key areas affecting the Yangtze rainfall are the western Pacific warm pool on the interannual time scale and the EINO3 area on the decadal time scale, respectively. The circulation anomaly associated with the interan- nual variation occurs in the upper troposphere whereas that associated with the decadal variation appears in the lower troposphere.
