初始扰动对静力适应过程的影响

本文从描述非静态、可压缩、等温干大气静力适应过程的线性模型出发，利用均匀介质中的波动理论，研究了初始扰动对静力适应过程中物理量场适应方向的影响；从能量分配和转换的角度探讨了静力平衡破坏后大气运动的物理本质.理论结果显示，当大气静力平衡被破坏后，垂直气压梯度场和密度场、垂直气压梯度场和水平流场u分量之间相互适应的因果关系受波动螺旋结构、水平基流及初始扰动性质等因素的影响，其中，初始扰动性质决定了声重力波各分支在静力适应过程中的贡献大小，从而影响各物理量场随时间的演变.在水平基流为西风急流的条件下，中尺度系统对初始扰动性质较敏感，初始速度扰动和密度扰动破坏静力平衡的前20分钟内，有垂直气压梯度场向浮力场适应，初始气压扰动破坏静力平衡的前期和后期，有浮力场向垂直气压梯度场适应，而中期，适应方向相反；垂直气压梯度场和水平流场u分量之间的适应关系对初始扰动性质不敏感但对扰动尺度较敏感；实验表明，当静力平衡被破坏后，在微尺度系统中，垂直气压梯度场是大气运动的因，而在中尺度系统中，水平流场u分量是大气运动的因.同时，初始扰动的性质影响适应过程中扰动能量的分配比例和扰动能量之间的转换情况，不同性质的初始扰动，引起大气运动的物理本质不同.

The effect of initial perturbation on the hydrostatic adjustment

The effect of initial perturbation on the hydrostatic adjustment is investigated based on the linear model describing the dynamics and thermodynamics of a non-static, compressible and isothermal dry atmosphere. The direction of adjustment between the vertical gradient of pressure field and the buoyance field is examined by using the wave theory in the homogeneous medium; and the physical essence of atmospheric movement is presented from the perspective of energy partition and conversion during the hydrostatic adjustment. The theoretical results show that the causal relationships between the vertical gradient of pressure field and the buoyancy field, the u branch of horizontal flow field and the vertical gradient of pressure field are affected by the helical structure of wave, the horizontal basic flow and the initial perturbation properties during the balance of atmospheric static equilibrium is destroyed, where the characteristic of initial perturbation determines the contribution of each branch of the acoustic-gravity waves in the process of hydrostatic adjustment, and affecting the evolution of the physical fields with time.