加速度迁移项位势及其在高原低涡及台风系统分析中的应用

依据水平风矢量场的分解思路,应用调和-余弦的二维风场分解方法,对水平风场的加速度迁移项也进行调和-余弦的分解,引入加速度迁移项位势概念,用加速度迁移项对应的位势分量部分对东移高原低涡及登陆台风系统的演变过程进行分析.结果表明:加速度迁移项位势对东移高原低涡系统有较好的描述作用.利用加速度迁移项位势追踪东移的高原低涡系统比常用的500 hPa位势高度场对低涡进行追踪更为清晰.此外,加速度迁移项位势在登陆台风Bilis的分析中也有较好的应用,可用以指示台风系统,判断台风中心的位置以及表示台风强度的变化.由于加速度迁移项位势可反映出水平风场平流的辐合辐散特征,因此对低涡及台风等与平流场的辐合辐散关系密切的天气系统的动力结构有较好的识别能力,可以作为一个新的动力诊断变量来诊断示踪天气系统的演变.

The relocation term in acceleration potential and its application in analyzing the Tibetan Plateau vortex and typhoon

Based on the same ideas of wind decomposition and using the harmonic-cosine methods, by introducing the concept of the relocation term in acceleration (RTA) potential, the RTA is decomposed into two parts: the rotational part and divergent part. The RTA potential corresponding to the divergent part of advection is used for diagnosing a Tibetan Plateau vortex and typhoon Bilis (0604). The results show that RTA potential can depict the Tibetan Plateau vortex well, and it is clearer to describe the low systems on the Tibetan plateau than potential height at 500hPa; besides that, it is also a good signal to identity the center and strength of typhoon Bilis. For the reason that RTA potential can reflect the divergence and convergence of horizontal advection, it has advantages in distinguishing vortexes in which the wind advection plays an important role.