中层和热层大气的垂直动力传输及其影响

本文根据气体分子运动论导出了垂直动力传输函数,此函数可以代替Nicolet和Mangc的混合比,较好地描述高层大气中从完全混合状态向扩散分离状态的过渡过程。分析了高层大气中湍流运动的观测结果,给出了湍流系数随高度分布的几个模式,利用这些模式计算了惰性气体氩、氦与氮的数密度比的高度剖面,并与箭载质谱仪探空资料作了比较。根据光化-动力传输理论,计算了上中层及低热层大气主要化学成份的高度分布。结果表明:垂直动力传输明显地影响着大气成份的分布。文中还指出,氧分子的光离解系数与其数密度的高度剖面耦合在一起,因而应当由上向下数值求解有源有汇的连续方程组,这样可避免由于光离解系数的假设所造成的误差。

ON THE VERTICAL DYNAMIC TRANSPORT AND ITS EFFECTS IN THE UPPER MESOSPHERE AND LOWER THERMOSPHERE

A formula for vertical dynamic transport function is deduced from the molecular kinetic theory of gases. Instead of Nicolet-Mange's "mixing ratio", this formula can describe successfully the transition process from mixing to separation conditions in the upper atmosphere. Considering the observational data of turbulence motion in the upper atmosphere, the distribution models of diffusion coefficient with height are presented, according to which the height distribution profiles of number density ratio, such as n（Ar）/n（N2）, n（He）/n（N2）, are calculated and compared with the rocket-borne mass-spectrometer's data. The distributions of main chemical components with height in the upper mesosphere and lower thermosphere are computed according to photochemical-dynamical transport theory. It is concluded, that photodissociation coefficient is coup-led with number density profiles of molecular oxygen, and the system of equations in-volved must be solved numerically from upper to lower heights, in order to diminish the errors arising from the assumption of photodissociation coefficient in computations.