定量分析几种Q矢量
Quantitative Analyses of Several Q Vectors
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摘要: 结合1991年7月5日20:00~6日20:00一次典型的江淮梅雨锋暴雨过程,从台站实际业务工作需要考虑,细致、具体地比较分析了850 hPa、700 hPa及500 hPa 3个层次的准地转 Q 矢量散度场、半地转 Q 矢量散度场、非地转 Q 矢量散度场及湿 Q 矢量散度场与相应时刻地面降水场对应关系的差异,同时还针对每一种 Q 矢量,将其在850 hPa、700 hPa及500 hPa 3个层次的散度场对同时刻降水场的反映能力进行了比较。在定量比较的基础上,得到了对4种 Q 矢量诊断特性的具体认识:(1)在整个梅雨锋暴雨过程中,3个层次的半地转 Q 矢量散度场及准地转 Q 矢量散度场对雨区的反映能力较小,而非地转 Q 矢量的散度场和湿 Q 矢量的散度场对雨区的反映能力明显较前二者大,尤其是湿 Q 矢量散度场在每个层次的诊断能力基本都大于相应层次的其它 Q 矢量的散度场。(2)对于每一种 Q 矢量而言,基本都是在700 hPa的散度场与雨区的对应关系好于各自在850 hPa和500 hPa的散度场,尤其是700 hPa湿 Q 矢量散度辐合场对同时刻梅雨锋暴雨的强度及落区都有很好的指示作用。最后,基于理论的角度对各 Q 矢量的诊断特性进行了较为深入地探讨和比较分析,明确地指出了4种 Q 矢量存在理论前提上的差异。Abstract: Considering a typical Jiang-Huai Meiyu rainstorm event during 5-6 July, 1991 and the operational requirements, the differences of the capability of reflecting precipitation area among quasi-geostropic-, semi-geostrophic-, ageostrophic- and wet-Q vector divergence fields at 850 hPa, 700 hPa and 500 hPa are examined in detail; in the meanwhile, the capability of reflecting precipitation area for each Q vector itself in the divergence fields at the three layers is analyzed. On a quantitative comparison basis, the diagnostic features of the four Q vectors are obtained: (1) quasi-geostropic- and semi-geostrophic-Q vector divergence fields at the three layers respond less obviously to the synchronous rainfall, while ageostrophic- and wet-Q vector divergence fields are better than previous two; especially, the diagnostic capability of the wet-Q vector divergence field at each layer is greater than those of the others throughout the Meiyu-front rainstorm. (2) As far as each Q vector is concerned, the 700 hPa convergence field basically has good capability of reflecting precipitation area than those at the other two layers; in particular, the convergence of the wet-Q vector divergence at 700 hPa serves as a good indicator of precipitation intensity and fallout region. At last, the diagnostic property of each Q vector is documented on a theoretical basis, and not only the theoretical differences among four Q vectors are depicted in full but the results form the quantitative comparison are confirmed theoretically as well.
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Key words:
- Q vector;
- Divergence field;
- Quantitative analysis;
- Meiyu front rainstorm
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