大气和海洋中一类中尺度边界急流的形成理论

对一个非地转线性浅水模式的研究表明,当背景场为大尺度径向地转流V_g时,在山地或海岸附近可以形成一类中尺度边界急流,其特征宽度为L_c=L₀（c₀/V_g）,式中c₀=（gH）^1/2为考虑了密度垂直差后的重力波波速,L₀=c₀/f为Rossby变形半径,f为柯利奥来参数。一般来说,L_c的量级在大气和海洋中分别为百公里和几十公里。由于大尺度地转流是形成这类中尺度边界急流的重要条件,因此从这一观点看,在大气中的这类急流,在亚洲东部一般只能在春末或夏季出现,因为在这些季节,在这一地区盛行大尺度的西南或东南季风。对海洋,这类中尺度边界急流可以出现在海洋的东西两岸,不具有明显的季节变化,即是一类半永久持续系统。

FORMATION OF A KIND OF LATERAL BOUNDARY MESO-SCALE JET IN THE ATMOSPHERE AND OCEAN

By using an ageostrophic shallow water model, it is pointed out that a kind of lateral boundary meso-scale jet can be established near the plateau or coast. The characteristic width of this kind of jet is proportional to the scale of L_c=L₀（c₀/_Vg）, where L₀=c₀/f is the radius of Rossby deformation, c₀=（g*H）1/2 the speed of gravity wave and Vg the large-scale geostrophic jet in the background. In general, L_c is of the order of one hundred kilometers and tens of kilometers in the atmosphere and in the ocean respectively. The large-scale geostrophic current is an important background condition for forming this kind of jet. From this view point it seems that this kind of atmospheric meso-scale jet. only occurs in late spring and summer in the eastern part of Asia, because there is a large-scale, south-west or south-east monsoon over there. For the ocean, this kind of meso-scale jet seems to be a semi-persistant system and not to show a significant seasonal variation, and it can be established in both sides of the ocean.