华东沿海地形对登陆热带气旋运动影响的理想数值研究

利用中尺度数值模式设计一组高分辨率理想试验,采用位涡趋势方法定量诊断分析热带气旋在登陆我国华东沿海地形时,其运动发生的精细化变化以及不同因子的贡献。结果表明,平地的存在使得登陆热带气旋移速相对更快,当华东沿海地形存在时,热带气旋移速显著增大,这种增速现象主要是由于平地和地形所引起的非对称气流以及相应的引导气流变化所致,这很可能是导致预报路径误差的一个重要原因。平地试验中,陆地在热带气旋低层激发出中小尺度的非对称气流,与之不同的是,实际地形的加入激发出更大尺度并且更强的非对称偏南气流。位涡趋势方法的诊断结果表明,非引导效应总体而言对热带气旋运动贡献较小,这是因为这些因子相互抵消,但在不同的垂直层次上,不同的非引导因子贡献存在明显的差异。

Idealized numerical study on influence of topography along East China coast on landfall tropical cyclone motion

Most previous studies have paid much attention on changes in landfall tropical cyclone(TC) motion caused by island topography and land drift induced by flat terrain roughness but rarely focused on influences of continental topography.In this study,the landfall tropical cyclone movement changes are examined in the presence of the influences of topography and environmental flows through numerical experiments,in which an initially axisymmetric vortex makes landfall on East China coastal areas.It is found that the flat land can bring about an acceleration of tropical cyclone during landfall while the increase in tropical cyclone speed is much larger,which is attributed to the increase of steering flows.The increase of speed has not been revealed in previous studies and may be an important attribution to TC track prediction error.Of more importance is that the flat land can induce asymmetric flow within the tropical cyclone regions while the asymmetric flows induced by topography are much stronger.Non-steering factors tend to counteract between one another and contribute little to the landfall tropical cyclone motion in general but different factors have individual contributions on different vertical layers.