对流层上传重力波的非线性演化

利用二维全隐欧拉格式对重力波在可压、非等温大气中的非线性传播过程进行了数值模拟和分析.分析结果表明，从对流层顶激发的重力波能稳定地经平流层传到中层顶，从而将能量和动量从一个区域带到另一个区域；在向上传播过程中，重力波经历了发展、位温翻转、对流直至最终破碎的演变；重力波的破碎是对流和小尺度波动的重要的源，对流不稳定和翻转是非线性现象的一个基本特征.计算还显示，扰动源的大小直接影响着重力波的非线性传播过程，当扰动源足够小时，重力波能稳定传播，而大振幅扰动可以加速重力波的破碎.

NONLINEAR EVOLUTION OF A GRAVITY WAVE PROPAGATING FROM THE TROPOPAUSE

By using a Full Implicite Continuous Eulerian （FICE） scheme, a two dimensional numerical model for describing nonlinear propagation of a gravity wave in the compressible and nonisothermal atmosphere is established. The result shows that gravity wave excited by the tropopause forcing can propagate stably to the mesosphere through the stratosphere so that the energy and momentum can be transferred from a region to another. In the propagation, gravity wave undergoes growth, overturning, convection and breaking. The breaking of gravity wave is the important source of convection and smallscale waves, and convective instability and overturn are the character of nonlinear phenomenon. It can be inferred that the size of the perturbing source affects directly the propagation of nonlinear gravity wave. When the source is sufficiently small gravity wave can propagate stably, and large amplitude forcing can accelerate the breaking of gravity wave.