复杂构型涡旋能量频散波列的形成过程

能量频散是一个基础性的科学问题,与台风、暴雨以及地震等灾害密切相关,一直受到多学科研究人员和广大预报员的关注。孤立圆涡能量频散波列形成过程己经清楚。但是,造成天气灾害的往往是非孤立圆涡,这里,非孤立圆涡指的是:一个热带气旋(Tropical Cyclone,TC)涡旋和一个中尺度涡构成的复杂构型。非孤立圆涡能量频散波列的形成过程研究目前尚未见报道。本文用线性化的正压无辐散涡度方程,研究了复杂构型的非孤立圆涡能量频散波列的形成过程,并指出该形成过程由三个阶段构成:涡旋东西向非对称结构的形成;涡旋主体东侧,频散高值系统的出现、持续和发展;在频散高值系统的东侧,频散低值系统的出现和加强。这些结果在台风预测中具有应用前景。

Formation process of a wave train created by the energy dispersion of a complex structure non-isolated vortex

Two numerical simulations whose integration times are 144 h are performed using a linearized non-divergent barotropic vorticity equation model to investigation into the formation process of a wave train induced by the energy dispersion of a complex structure non-isolated vortex.In the initial field a tropical cyclone (TC) vortex and a mesoscale vortex coexist,which forms a complex structure pattern in the first simulation.The results in the first simulation show that a TC-high-low wave train may be created by the energy dispersion of the complex structure non-isolated vortex.The formation of the wave train was composed of three stages: (1) an asymmetric structure in the east-west direction in the TC area emerged,(2) a high dispersion system occurred,was maintained and strengthened to the east of the TC vortex,and (3) a low dispersion system occurs and then intensifies to the east of the high dispersion system.In the initial field there is only one tropical cyclone vortex,which forms an isolated circular vortex pattern rather then a complex structure pattern in the second simulation.The results in the second simulation show that a TC-high-low wave train can be identified.Compared with the case of the isolated circular vortex,three differences exhibit in the case of the complex structure vortex.Firstly,the first stage of the wave train formation is significantly shortened.Secondly,the dispersion high is stronger.Thirdly,the dispersion low has a larger spatial scale.The results have following application prospects.(1) TC is often located on the southern side of the subtropical high,the dispersion high system occurs on the east side of the TC,while TC moves from the east to the west under the influence of the steering flow.Sometimes the dispersion high can be connected with the subtropical high,which extends to the south,and TC track turns abruptly to the north from the west.In most cases,the subtropical high and the dispersion high is far away from each other,therefore they cannot be connected.The results in this paper show that the dispersion high is stronger in the case of complex structure configuration vortex,it will be in favor of their connection and leads to the unusual track of the TC.(2) Normally there is less moisture with low probability of a new TC genesis in the dispersion high area,and vice versa.The results in this paper show that in the case of the complex structure vortex the dispersion low system extends to a large area,and the high probability region of a new TC genesis will be enlarged as well.