登陆台风莫拉克(2009)的涡度拟能收支分析

Analysis of the budget of enstrophy during the landing of Typhoon Morakot (2009)

中文关键词:  涡度拟能  散度能量  变形能量

英文关键词:Vorticity enstrophy  Divergence energy  Deformation energy

中文摘要:

      利用涡度拟能、散度平方项(简记为散度能量)和总变形平方项(简记为变形能量)来表征涡度、散度和变形的强度,并推导这3个物理量的倾向方程.这些方程中既包含代表这些物理量相互转化的符号相反项,也含有代表共同强迫的符号相同项,其中,涡度拟能局地变化主要由涡度拟能与变形能量的共同强迫项、涡度拟能与变形能量的转化项以及涡度拟能与散度能量的转化项组成.针对2009年第8号台风莫拉克,利用美国全球预报系统分析场资料计算这些方程中的强迫项,分析涡度拟能及其收支特征,以此来探讨影响台风莫拉克涡度拟能局地变化的主要物理因素.结果表明,在莫拉克发展和衰减阶段,涡度拟能与变形能量的共同强迫项(涡-形相同项)和涡度拟能与散度能量的转化项(涡-散转化项)是影响涡度拟能局地变化的重要强迫项.涡度拟能与变形能量转化项(涡-形转化项)的贡献相对来说弱一些.影响位涡拟能局地变化的重要物理因素是涡-形相同项和涡-形转化项中的平流输送项和散度耦合项,以及涡-散转化项中散度耦合项.变形能量一方面通过涡-形转化项向涡度拟能转化,直接促进涡度拟能增长；另一方面通过散-形转化项向散度能量转化,再通过涡-散转化项散度能量向涡度拟能转化,间接促进涡度拟能增长.

英文摘要:

      The vorticity enstrophy, divergence energy and deformation energy are introduced in this paper.By deriving their tendency equations which contain both terms of identical signs and those of opposite signs, the interactions between the rotational, divergent and deformational fields can be studied.In the landing process of Typhoon Morakot in Taiwan in 2009, all the three variables and terms in their tendency equations are calculated.The results show that in the stages of development and decay of Morokat, the exchange between vorticity enstrophy and divergence energy and the external forcing of vorticity enstrophy play the most important role in the local change of vorticity enstrophy, while the effect of the exchange between vorticity enstrophy and deformation energy is relatively small.On the whole (both the spatial and time averages), the exchanges between the three variables in the center areas of the typhoon are favorable to the development of vorticity enstrophy.The deformation energy transforms to vorticity enstrophy by the vorticity-deformation transition term, which increases the vorticity enstrophy.In the same time, the deformation energy transforms to the divergence energy by the divergence-deformation transition term, which increases the divergence energy.Then the divergence energy transforms to vorticity enstrophy by the vorticity-divergence transition term, which represents the influence of deformation energy on vorticity enstrophy.